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Controllable synthesis of efficient Ru-doped PtSn alloy nanoplate electrocatalysts for methanol oxidation reaction
Abstract
Platinum (Pt) is considered as the preferred metal catalyst for methanol oxidation reactions. However, the application prospects of Pt catalysts are limited due to the inherent scarcity and cost. Enabling a trace amount of Pt to exert satisfactory catalytic activity and durability has become a key issue in designing electrocatalysts. Here, Ru-doped PtSn alloy nanoplates ([email protected] NP) with an average particle size of less than 5 nm were controllably synthesized by adjusting the Pt–Sn atomic ratio. Compared with Ru-doped PtSn alloy nanospheres ([email protected] NS/C, 714.7 mA/mgPt), PtSn bimetallic nanoplates (PtSn NP/C, 880.2 mA/mgPt) and commercial Pt/C (299.6 mA/mgPt), the prepared [email protected] NP/C (1105.1 mA/mgPt) exhibited an extraordinary methanol oxidation mass activity. Furthermore, the peak oxidation current retention of [email protected] NP/C was as high as at 87.5% after 1000 accelerated durability tests. The significantly enhanced catalytic performance and durability were attributed to the synergistic effect of the alloy components and morphological advantages. This work has led us to think more deeply about the constitutive relationship between structure and performance.
... Alternatively, Pt-Ni supported on graphene also displayed good MOR activity in previous reports [10,13]. Another effective approach is to introduce a second oxyphilic metal, such as Ru, In and Sn, to adsorb hydroxyl species and to oxidate the adsorbed CO, which is referred to as a bifunctional effect [14][15][16][17][18] [19]. ...
Direct methanol fuel cells (DMFC) have attracted increasing research interest recently; however, their output performance is severely hindered by the sluggish kinetics of the methanol oxidation reaction (MOR) at the anode. Herein, unique hierarchical Pt-In NWs with uneven surface and abundant high-index facets are developed as efficient MOR electrocatalysts in acidic electrolytes. The developed hierarchical Pt89In11 NWs exhibit high MOR mass activity and specific activity of 1.42 A mgPt-1 and 6.2 mA cm-2, which are 5.2 and 14.4 times those of Pt/C, respectively, outperforming most of the reported MORs. In chronoamperometry tests, the hierarchical Pt89In11 NWs demonstrate a longer half-life time than Pt/C, suggesting the better CO tolerance of Pt89In11 NWs. After stability, the MOR activity can be recovered by cycling. XPS, CV measurement and CO stripping voltammetry measurements demonstrate that the outstanding catalytic activity may be attributed to the facile removal of CO due to the presence of In site-adsorbing hydroxyl species.
Alloying Pt with foreign metal to modulate the electronic structure and controlling the geometric morphology of Pt nanomaterials to tailor the surface structure are two extensively applied strategies to promote the electrocatalytic activity of Pt nanomaterials in fuel cell reactions. The former enhances the intrinsic catalytic activity of the nano-catalysts while the latter increases the number of active sites for catalytic reactions. So why not combine the two strategies to construct highly efficient Pt-based nano-catalysts? Within this work, we successfully synthesized one-dimensional PtPd nanowires through a one-pot method by exploiting the similarities of Pt and Pd, like identical lattice constants. The as-prepared products had alloyed structures and ultrafine profiles of nanowires. The electrochemical test indicated that the PtPd nanowires as-prepared possessed superior catalytic activity to methanol oxidation reaction with the mass activity of 2071 mAmg⁻¹, significantly better than that of the commercial Pt/C (473 mAmg⁻¹). Density functional theory calculation showed that with the introduction of Pd, the d-band electron center of Pt would downshift and the adsorbed interaction between CO intermediates (CO∗) with the surface of catalysts would diminish, which would improve the resistance of the catalysts to the toxicity of CO∗, thus enhancing the electro-catalytic activity and stability. Apart from the alloying effect, the unique structure of the one-dimensional ultra-fine nanowires could guarantee adequate atoms would be involved to expose and provide sufficient active sites for reactions, which was another essential factor in the promotion of the electro-catalytic performance.
Electrocatalytic water-gas shift reaction (EWGSR) at room temperature and atmospheric pressure is an emerging process for high-pure hydrogen production without an additional H2 separation procedure. Therefore, developing efficient electrocatalysts of EWGSR is one of the critical factors for its wide applications. Herein, the effects of support and calcinated temperature on the EWGSR performance are highlighted by systematically investigating the Pt/γ-Fe2O3, Pt/CeO2, Pt/TiO2, and Pt/α-Fe2O3 catalysts. The results reveal that the γ-Fe2O3 supported Pt catalyst (calcined at 400 °C) exhibits the lowest anodic onset potential and the highest activity compared to these prepared catalysts, and the mass activity is 3.5 times as high as 20% Pt/C. Furthermore, the onset potential for the EWGSR shows a strong correlation with the active O in the amorphous PtOx structures, where the active O atoms can promote the activation of the OH⁻ and reduce the onset potential of the reaction. The significantly enhanced catalytic performance and durability are more responsible for the exposed Pt⁰ and the weak adsorption of CO on the Pt/γ-Fe2O3 catalyst. This study provides a new and promising route for designing excellent Pt catalysts for EWGSR in the hope that it can be helpful to the scholars in this orientation.
The emergence of platinum‐based catalysts promotes efficient methanol oxidation reactions (MOR). However, the defects of such noble metal catalysts are high cost, easy poisoning, and limited commercial applications. The efficient utilization of a low‐cost, anti‐poisoning catalyst has been expected. Here, it is skillfully used N‐doped graphdiyne (NGDY) to prepare a zero‐valent platinum atomic catalyst (Pt/NGDY), which shows excellent activity, high pH adaptability, and high CO tolerance for MOR. The Pt/NGDY electrocatalysts for MOR with specific activity 154.2 mA cm−2 (1449.3 mA mgPt−1), 29 mA cm−2 (296 mA mgPt−1) and 22 mA cm−2 (110 mA mgPt−1) in alkaline, acid, and neutral solutions. The specific activity of Pt/NGDY is 9 times larger than Pt/C in alkaline solution. Density functional theory (DFT) calculations confirm that the incorporation of electronegativity nitrogen atoms can increase the high coverage of Pt to achieve a unique atomic state, in which the shared contributions of different Pt sites reach the balance between the electroactivity and the stability to guarantee the higher performance of MOR and durability with superior anti‐poisoning effect. Independent zero‐valent Pt atoms on N‐doped GDY to prepare a zero‐valent platinum atomic catalyst (Pt/NGDY) are skilfully anchored. The results reveal that the inhomogeneous electronic distribution of NGDY allows the dispersive and high coverage of Pt atoms, boosting up the electroactivity for efficient methonal oxidation reaction (MOR). The Pt/NGDY electrocatalysts exhibit higher specific activity for MOR than commercial Pt/C.
Single Pt atom catalysts are key targets because a high exposure of Pt substantially enhances electrocatalytic activity. In addition, PtRu alloy nanoparticles are the most active catalysts for the methanol oxidation reaction. To combine the exceptional activity of single Pt atom catalysts with an active Ru support we must overcome the synthetic challenge of forming single Pt atoms on noble metal nanoparticles. Here we demonstrate a process that grows and spreads Pt islands on Ru branched nanoparticles to create single-Pt-atom-on-Ru catalysts. By following the spreading process by in situ TEM, we found that the formation of a stable single atom structure is thermodynamically driven by the formation of strong Pt–Ru bonds and the lowering of the surface energy of the Pt islands. The stability of the single-Pt-atom-on-Ru structure and its resilience to CO poisoning result in a high current density and mass activity for the methanol oxidation reaction over time. PtRu nanoparticles are the state-of-the-art catalysts for methanol electrooxidation—the anodic reaction in direct methanol fuel cells. Now, a method of dispersing single Pt atoms over Ru nanoparticles is presented and monitored in situ, thereby boosting the catalytic performance in the methanol oxidation reaction.
Li–CO2 batteries provide the possibility for synchronous implementation of carbon neutrality and development of advanced energy storage devices. Catalytic cathodes composed of well‐designed conductive substrates and active materials are critical to the improvement of Li–CO2 batteries. Herein, MnOx‐CeO2 hollow nanospheres are strung together by conductive polypyrrole (PPy) via post‐in‐situ polymerization, and a necklace‐like MnOx‐CeO2@PPy hierarchical cathode with excellent flexibility and self‐supporting feature is constructed. Benefitting from the excellent conductivity of PPy, the binder‐free structure, and the greatly exposed catalytic active sites, the MnOx‐CeO2@PPy based Li–CO2 batteries exhibit superior discharge capacity (13631 mA h g–1 at 100 mA g–1) and cycle performance (253 cycles) as well as a low overpotential of 1.49 V. Of particular note, the flexible freestanding film is confirmed as a potential catalytic cathode for flexible Li–CO2 batteries. The density functional theory calculations, combined with experimental tests, are performed to gain insights into the enhanced substrate adsorption capacity, the optimized electronic structure of the active surface MnOx‐CeO2 (111), the concentrated electrons on the reaction sites Ce, and the electrochemical mechanism. This work initiates the use of conductive polymers for catalytic cathodes in Li–CO2 batteries, which provide new opportunities for promoting the performance of various energy storage devices.
We report a general concurrent template strategy for precise synthesis of mesoporous Pt‐/Pd‐based intermetallic nanoparticles with desired morphology and ordered mesostructure. The concurrent template not only supplies a mesoporous metal seed for re‐crystallization growth of atomically ordered intermetallic phases with unique atomic stoichiometry but also provides a nanoconfinement environment for nanocasting synthesis of mesoporous nanoparticles with ordered mesostructure and rhombic dodecahedral morphology under elevated temperature. Using the selective hydrogenation of 3‐nitrophenylacetylene as a proof‐of‐concept catalytic reaction, mesoporous intermetallic PtSn nanoparticles exhibited remarkably controllable intermetallic phase‐dependent catalytic selectivity and excellent catalytic stability. This work provides a very powerful strategy for precise preparation of ordered mesoporous intermetallic nanocrystals for application in selective catalysis and fuel cell electrocatalysis.
Developing low cost, highly efficient, and long-term stability electrocatalysts are critical for direct oxidation methanol fuel cell. Despite huge efforts, designing low-cost electrocatalysts with high activity and long-term durability remains a significant technical challenge. Here, we prepared a new kind of platinum-nickel catalyst supported on silane-modified graphene oxide (NH2-rGO) by a two-step method at room temperature. Powder X-ray diffraction, UV–vis spectroscopy, Raman, FTIR spectroscopy and X-ray photoelectron spectroscopy results confirm that GO was successfully modified with 3-aminopropyltriethoxysilane (APTES), which helps to uniformly disperse PtNi nanoparticles. Cyclic voltammetry, chronoamperometry, CO-stripping and rotating disk electrode (RDE) results imply that PtNi/NH2-rGO catalyst has significantly higher catalytic activity, enhance the CO toxicity resistance, higher stability and much faster kinetics of methanol oxidation than commercial Pt/C under alkaline conditions.
Direct methanol fuel cell (DMFC) has been considered as an ideal “green” energy converter because of its high energy-conversion efficiency and low pollution emissions, while the high costs and poor...
Phase engineering of nanomaterials (PEN) offers a promising route to rationally tune the physicochemical properties of nanomaterials and further enhance their performance in various applications. However, it remains a great challenge to construct well‐defined crystalline@amorphous core–shell heterostructured nanomaterials with the same chemical components. Herein, the synthesis of binary (Pd‐P) crystalline@amorphous heterostructured nanoplates using Cu3−χP nanoplates as templates, via cation exchange, is reported. The obtained nanoplate possesses a crystalline core and an amorphous shell with the same elemental components, referred to as c‐Pd‐P@a‐Pd‐P. Moreover, the obtained c‐Pd‐P@a‐Pd‐P nanoplates can serve as templates to be further alloyed with Ni, forming ternary (Pd‐Ni‐P) crystalline@amorphous heterostructured nanoplates, referred to as c‐Pd‐Ni‐P@a‐Pd‐Ni‐P. The atomic content of Ni in the c‐Pd‐Ni‐P@a‐Pd‐Ni‐P nanoplates can be tuned in the range from 9.47 to 38.61 at%. When used as a catalyst, the c‐Pd‐Ni‐P@a‐Pd‐Ni‐P nanoplates with 9.47 at% Ni exhibit excellent electrocatalytic activity toward ethanol oxidation, showing a high mass current density up to 3.05 A mgPd−1, which is 4.5 times that of the commercial Pd/C catalyst (0.68 A mgPd−1). Binary (Pd‐P) and ternary (Pd‐Ni‐P) nanoplates, both with crystalline@amorphous core–shell nanostructures, are synthesized using Cu3−χP nanoplates as templates. The obtained c‐Pd‐Ni‐P@a‐Pd‐Ni‐P heterostructured nanoplates exhibit superior electrocatalytic performance toward the ethanol oxidation reaction in alkaline media compared to c‐Pd‐P@a‐Pd‐P heterostructured nanoplates and commercial Pd/C catalysts.
Palladium (Pd) nanostructures are highly active non‐platinum anodic electrocatalysts in alkaline direct methanol fuel cells (ADMFCs) and their electrocatalytic performance relies highly on their morphology and composition. Herein, a facile high‐temperature pyrolysis method to synthesize high‐quality Pd‐palladium oxide (PdO) porous nanotubes (PNTs) by using Pd(II)‐dimethylglyoxime complex (Pd(II)‐DMG) nanorods as a self‐template is reported. The chemical component of pyrolysis products highly correlates with pyrolysis temperature. The electrochemical measurements and density functional theory calculations show the existence of PdO enhances the electroactivity of metallic Pd for both methanol oxidation reaction (MOR) and carbon monoxide oxidation reaction in alkaline media. Benefiting from its one‐dimensionally porous architecture and evident synergistic effect between PdO and Pd (e.g., electronic effect and bifunctional mechanism), Pd‐PdO PNTs achieve a 3.7‐fold mass activity enhancement and improved durability for MOR compared to commercial Pd nanocrystals. Considering the simple synthesis, excellent activity, and long‐term stability, Pd‐PdO PNTs may be highly promising anodic electrocatalysts in ADMFCs. High‐quality porous palladium (Pd)‐palladium oxide (PdO) nanotubes are synthesized via a facial Pd(II)‐dimethylglyoxime complex nanorods‐induced self‐template method. Benefiting from the one‐dimensionally porous architecture and evident synergistic effect between PdO and Pd, the Pd‐PdO nanotubes achieve 3.7‐fold mass activity enhancement and improved durability for methanol oxidation reaction compared to commercial Pd nanocrystals, revealing a highly promising robust anodic electrocatalyst in alkaline direct methanol fuel cells.
Download this Open Access article at: http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.7b02166
The oxidation of adsorbed CO is a key reaction in electrocatalysis. It has been studied extensively on both extended model surfaces and on nanoparticles, however correlation between the two is far from simple. Molecular insight into the reaction is often provided using in situ IR spectroscopy, however practical challenges mean in situ studies on nanoparticles have yet to provide the same level of detail as those on model surfaces. Here we use a new approach to in situ IR spectroscopy to study the mechanism of CO adlayer oxidation on a commercial carbon-supported Pt catalyst. We observe bipolar IR absorption bands but develop a simple model to enable fitting. Quantitative analysis of band behavior during the oxidation pre-peak using the model agrees well with previous analysis based on conventional absorption bands. A second linear CO band is observed during the main oxidation region and is assigned to the distinct contribution of CO on step as opposed to terrace sites. Analysis of the step and terrace CO bands during oxidation shows that oxidation begins on the terraces of the nanoparticles before CO on steps is removed. Further correlation of this behavior with the current shows that step CO is only lost in the first of the 2 main oxidation peaks.
Methanol offers certain specific advantages over hydrogen; it is cheap, plentiful, and renewable from wood alcohol, and since it is a liquid, it is easily stored, transported, and distributed. A lower ionomer content limits the ionic conduction in the catalyst layer, while a higher ionomer content reduces the mass transport. Although the ionomer content controls the DMFC performance, the amount of ionomer used depends on the preparation method of the MEA. Therefore, the catalyst surface in the DMFC will be poisoned by many surface intermediates. Consequently, a suitable electrocatalyst must be developed that can resist poisoning by the surface intermediates created by partial oxidation. High efficiencies may be achieved because of the unique properties of nanomaterials, particularly vectorial transfer of charge in dimensionally modulated supports;90 additional benefits include the possibility of high surface areas, sufficient chemical resistivity, and superior mechanical strength.
The development of cathode oxygen reduction reaction (ORR) catalysts with high characteristics for practical, direct methanol fuel cells (DMFCs) has continuously increased the attention of researchers. In this work, interface-rich Au-doped PdBi (PdBiAu) branched one-dimensional (1D) alloyed nanochains assembled by sub-6.5 nm particles have been prepared, exhibiting an ORR mass activity (MA) of 6.40 A·mgPd⁻¹ and long-term durability of 5,000 cycles in an alkaline medium. The MA of PdBiAu nanochains is 46 times and 80 times higher than that of commercial Pt/C (0.14 A·mgPt⁻¹) and Pd/C (0.08 A·mgPd⁻¹). The MA of binary PdBi nanochains also reaches 5.71 A·mgPd⁻¹. Notably, the PdBiAu nanochains exhibit high in-situ carbon monoxide poisoning resistance and high methanol tolerance. In actual DMFC device tests, the PdBiAu nanochains enhance power density of 140.1 mW·cm⁻² (in O2)/112.4 mW·cm⁻² (in air) and durability compared with PdBi nanochains and Pt/C. The analysis of the structure—function relationship indicates that the enhanced performance of PdBiAu nanochains is attributed to integrated functions of surficial defect-rich 1D chain structure, improved charge transfer capability, downshift of the d-band center of Pd, as well as the synergistic effect derived from “Pd-Bi” and/or “Pd-Au” dual active sites. [Figure not available: see fulltext.].
The precise regulation for the structural properties of nanomaterials at the atomic scale is an effective strategy to develop high-performance catalysts. Herein, a facile dual-regulation approach was developed to successfully synthesize Ru1Ptn single atom alloy (SAA) with atomic Ru dispersed in Pt nanocrystals. High-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure demonstrated that Ru atoms were dispersed in Pt nanocrystals as single atoms. Impressively, the Ru1Ptn-SAA exhibited an ultrahigh specific activity (23.59 mA cm-2) and mass activity (2.805 mA/μg-PtRu) for methanol oxidation reaction (MOR) and exhibited excellent exchange current density activity (1.992 mA cm-2) and mass activity (4.71 mA/μg-PtRu) for hydrogen oxidation reaction (HOR). Density functional theory calculations revealed that the introduction of Ru atoms greatly reduced the reaction free energy for the decomposition of water molecules, which promoted the removal of CO* in the MOR process and adjusted the Gibbs free energy of hydrogen and hydroxyl adsorption to promote the HOR. Our work provided an effective idea for the development of high performance electrocatalysts.
Direct methanol fuel cells (DMFC), among the most suited and prospective alternatives for portable electronics, have lately been treated with nanotechnology. DMFCs may be able to remedy the energy security issue by having low operating temperatures, high conversion efficiencies, and minimal emission levels. Though, slow reaction kinetics are a significant restriction of DMFC, lowering efficiency and energy output. Nowadays, research is more focused on fundamental studies that are studying the factors that can improve the capacity and activity of catalysts. In DMFC, among the most widely explored catalysts are platinum and ruthenium which are enhanced in nature by the presence of supporting materials such as nanocarbons and metal oxides. As a result, this research sheds light on nanocatalyst development for DMFCs based on Platinum noble metal. To summarize, this research focuses on the structure of nanocatalysts, as well as support materials for nanocatalysts that can be 3D, 2D, 1D, or 0D. The support material described is made up of CNT, CNF, and CNW, which are the most extensively used because they improve the performance of catalysts in DMFCs. In addition, cost estimations for fuel cell technology are emphasized to show the technology's status and requirements. Finally, challenges to nanocatalyst development have been recognized, as well as future prospects, as recommendations for more innovative future research.
Nanoframe structures with rich defects are desirable in the field of catalysis, whereas the precise synthesis of them remains challenging. In this study, the defect-rich PtPdCu flower-like nanoframes have been successfully synthesized by oxidative etching of pre-prepared [email protected] core-shell nanoflowers. According to the experiment results, the formation of [email protected] core-shell nanoflowers plays a decisive role in synthesizing PtPdCu flower-like nanoframes. Due to its novel structures with rich defects and the synergistic effect between Pd, Cu and Pt, PtPdCu flower-like nanoframes exhibit enhanced catalytic activity. In special, the mass activity of PtPdCu flower-like nanoframes is 2.0 and 7.0 times as large as that of [email protected] core-shell nanoflowers and Pt black for MOR in acidic medium, respectively. Furthermore, PtPdCu flower-like nanoframes present exceptionally stability even after the long-term accelerating test.
Developing catalysts with high performance and low cost for methanol oxidation reaction (MOR) is the key to promoting the industrialization of direct methanol fuel cells (DMFCs). In this work, multiwalled carbon nanotubes (MWCNTs) supported PtCo alloys catalysts with improved MOR properties and anti-CO poisoning ability are successfully prepared by integrating low temperature adsorption and high temperature reduction method. The Pt1Co3@NC/MWCNTs sample with moderate Co²⁺ feeding content (0.81 mA/ugPt) achieves a factor of 1.93 enhancement in MOR mass activity compared to the commercial Pt/C catalyst (0.42 mA/ugPt). In addition, the Pt1Co3@NC/MWCNTs sample displays a lower CO oxidation onset potential respect to pristine Pt/C catalyst (0.74 V vs. 0.82 V). Scuh improvement of MOR activity, durability and anti-CO poisoning ability of the Pt1Co3@NC/MWCNTs catalyst is ascribed to the moderate surface compositions, optimal electronic interaction between PtCo alloys and MWCNTs, and the protection of N-doped carbon (NC) shells. This study provides a new direction to decrease the utilization of platinum and improve the MOR activity, stability and anti-CO poisoning ability of electrocatalysts which will be potential in design and fabrication of the highly efficient electrocatalysts for DMFCs applications.
For commercially viable direct methanol fuel cells, electrocatalysts play a crucial role in motivating the sluggish methanol oxidation reaction (MOR) over anode. Unfortunately, the large-scale applications of current MOR catalysts are hampered by their poor tolerance to poisoning and fast activity degradation. Herein, a unique composite catalyst comprised of partial Pd nanoparticles and partial Pd single atoms (PdNPs/Pd-Nx@C) is developed. The as-fabricated catalyst exhibits remarkable activity of 9.45 mA·cm⁻² towards MOR in alkaline solution, which is 7.05 and 3.92 times that of commercial Pd/C and nanoparticle type (PdNPs@C) electrocatalysts, respectively. Impressively, the PdNPs/Pd-Nx@C shows the highest long-time stability with 90.38% and 89.8% of the initial activity retained after 3600 s chronoamperometry (CA) test and 2000 cycles of cyclic voltammetry (CV) measurements with accelerated durability test (ADT), respectively. Combined with high-angle annular darkfield scanning transmission electron microscopy (HAADF-STEM), X-ray adsorption fine structure (XAFS) spectra and X-ray photoelectron spectroscopy (XPS) analyses, the superior performance of PdNPs/Pd-Nx@C can be ascribed to the synergistic effect from the Pd single atoms, N-doped carbon supports and Pd nanoparticles. Notably, the embedded Pd single atoms are liable to transfer electrons to the substrate due to the electronic metal-support interactions (EMSI) and the charge transfer between Pd nanoparticles and carbon supports is suppressed, inducing a weak adsorption strength of poisonous carbonous intermediate species on active Pd nanoparticles and improved poisoning tolerance in MOR process, which is verified by density functional theory (DFT) calculations as well as CO-stripping voltammetry experiments. This work not only contributes the first example of a synergistic catalyst between nanoparticles and single atoms for MOR but also deepens the knowledge on the metal-support interaction.
The fabrication of highly active and stable Pt-based catalysts is an essential factor for the large-scale development of direct methanol fuel cells (DMFC), which is currently hampered by inefficient metal utilization, vulnerability to the CO poisoning effect, and relatively sluggish reaction kinetics. Herein, porous graphene with morphology-controlled TiO2 supported Pt nanoparticles ([email protected]/graphene) as efficient catalysts for the methanol oxidation reaction (MOR) are investigated via an in situ UV-photo-assisted reduction strategy. It is found the TiO2 nanorods (TONR) with the optimal (001) and (110) facets effectively strengthen the Pt trapping ability, enhance the adsorption of methanol molecules and weaken CO intermediate poisoning compared to TiO2 nanocrystals (TONC). Importantly, both in acid and alkaline electrolytes, the [email protected]/GN catalysts exhibit superior catalytic activity (1945.63 mA mgPt-1/3165 mA mgPt-1) and long term durability for the MOR, outperforming most reported electrocatalysts. The outstanding catalytic properties are intrinsically attributed to well-hierarchical structure and strong metal-support interactions, which facilitate the tuning of surface properties and electronic structures, promote charge transfer, and synergistically boost methanol electrooxidation. This work indicates the importance of catalyst morphology/facet tuning for catalytic performance enhancement and provides a feasible idea for DMFC catalyst design and construction. This journal is
Binary PtCo, PtCu and ternary PtCoCu alloys with different surface element distributions were prepared to study the effect of composition on electrocatalytic hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR). A one-pot method was used to synthesize self-assembled alloy nanocrystals in one step. By adjusting the composition of synthesized alloys, their properties were optimized. The changes of morphology and property of the alloys after adding Cu were discussed. The HER and MOR properties of alloys were affected by the composition. Especially, the ternary alloy revealed better properties than that of the binary alloy. The starting potential of PtCoCu alloy in HER reaction under visible light is 14 mV and the overpotential under 10 mA cm⁻¹ is 44 mV, which revealed excellent cycle stability. The current density at 0.7 V for MOR reaction can reach 4.2 mA cm⁻¹. This is ascribed to the composition of alloy. Cu in alloys resulted in plasma-induced effective electron transfer. This result provides a feasible strategy for the design of effective multifunctional electrocatalysts.
A three-part nano-catalyst including ruthenium oxide, manganese cobalt oxide, and reduced graphene oxide nanosheet in form of RuO2-MnCo2O4/rGO is synthesized by one-step hydrothermal synthesis. The material is placed on a glassy carbon electrode (GCE) for electrochemical studies. The ability of these nano-catalysts in the oxidation process of methanol in an alkaline medium for usage in direct methanol fuel cells (DMFC) was examined with electrochemical tests of cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The effect of the addition of rGO to the nanocatalyst structure in the methanol oxidation reaction (MOR) process was investigated. We introduced the RuO2-MnCo2O4/rGO as a nanocatalyst with excellent cyclic stability of 97% after 5000 cycles in the MOR process. Besides, the study of the Tafel plots and the effect of temperature and scan rate in the MOR process showed that RuO2-MnCo2O4/rGO nanocatalyst has better electrochemical properties than MnCo2O4 and RuO2-MnCo2O4. This high electrocatalytic activity could be related to the synergistic effect of placement of metal oxides of ruthenium, manganese, and cobalt near each other and putting them on rGO, which enhances conductivity and surface area and improve electron transfer. The decrease in the resistance against charge transfer and the increment in the anodic current density illustrated that the reaction rate is enhanced at higher temperature. Thus RuO2-MnCo2O4/rGO shows robust stability and superior performance for MOR.
Li-CO2 batteries present considerable prospects both in resourcing CO2 and remedying the unsatisfied performance of current energy storage devices. Herein, a porous self-supporting cathode for Li-CO2 battery is fabricated through straightforward anchoring of two-dimensional (2D) cobalt-doped CeO2 nanosheets on graphene aerogel, bypassing the addition of binder and the complicated manufacturing process. The combination of CeO2 and Co3O4 results in the reorganization of electronic structure by strongly coupled nanointerfaces, enhancing the reversible formation and decomposition of Li2CO3. Meanwhile, the unique porous structure facilitates the diffusion of CO2 and electrolyte in Li-CO2 batteries. The as-assembled Li-CO2 battery achieves a superior discharge capacity (7860 mAh/g) and competitive cycling stability (>100 cycles). In particular, a flexible Li-CO2 battery is developed with the freestanding cathode, which can provide a stable power output during multi-angle bending and folding. The improved conductivity, CO2 adsorption ability and the electrochemical reaction pathway are revealed by density functional theory (DFT) calculations in detail. This work sheds new light on the development of advanced and flexible Li-CO2 batteries for wearable electronics.
Pt-based alloy nanomaterials with nanodendrites (NDs) structures are efficient electrocatalysts for methanol oxidation reaction (MOR), however their durability is greatly limited by the issue of transition metals dissolution. In this work, a facile trace Ir-doping strategy was proposed to fabricate Ir-PtZn and Ir-PtCu alloy NDs catalysts in aqueous medium, which significantly improved the electrocatalytic activity and durability for MOR. The as-prepared Ir-PtZn/Cu NDs catalysts showed distinct dendrites structures with the averaged diameter of 4.1 nm, and trace Ir doping subsequently improved the utilization of Pt atoms and promoted the oxidation efficiency of methanol. The electrochemical characterizations further demonstrated that the obtained Ir-PtZn/Cu NDs possessed enhanced mass activities of nearly 1.23 and 1.28-fold higher than those of undoped PtZn and PtCu, and approximately 2.35 and 2.67-fold higher than that of Pt/C in acid medium. More excitingly, after long-term durability test, the proposed Ir-PtZn and Ir-PtCu NDs still retained about 88.9% and 91.6% of its initial mass activities, which further highlights the key role of Ir-doping in determining catalyst performance. This work suggests that trace Ir-doping engineering could be a promising way to develop advanced electrocatalysts toward MOR for direct methanol fuel cell (DMFC) applications.
Noble-metal nanoframes consisting of interconnected, ultrathin ridges have received considerable attention in the field of heterogeneous catalysis. The enthusiasm arises from the high utilization efficiency of atoms for significantly reducing the material loading while enhancing the catalytic performance. In this review article, we offer a comprehensive assessment of research endeavors in the design and rational synthesis of noble-metal nanoframes for applications in catalysis. We start with a brief introduction to the unique characteristics of nanoframes, followed by a discussion of the synthetic strategies and their controls in terms of structure and composition. We then present case studies to elucidate mechanistic details behind the synthesis of mono-, bi-, and multimetallic nanoframes, as well as heterostructured and hybrid systems. We discuss their performance in electrocatalysis, thermal catalysis, and photocatalysis. Finally, we highlight recent progress in addressing the structural and compositional stability issues of nanoframes for the assurance of robustness in catalytic applications.
Direct methanol fuel cell has been widely recognized as the ideal renewable energy conversion device. However, it still suffers from two major limitations: the heavy use of precious metal platinum and the sluggish kinetics of methanol oxidation catalytic reaction, which have prevented its large-scale commercialization. Therefore, it is considered desirable to design rational and greatly effective catalysts. In this work, multi-dimensional ternary composite electrocatalysts of Pt/Ni(OH)2/nitrogen-doped graphene catalysts have been synthesized with 0D Pt nanoparticles on the 2D Ni(OH)2 nanosheets supported by 3D porous nitrogen-doped graphene hydrogel, and with a low amount (4.26 wt%) of Pt. Notably, the multi-dimensional porous structure design, abundant hydroxyl species, and mutual interactions of ternary catalysts endow high activity promoting the poisonous CO or CO-like intermediates oxidation and propelling the kinetics of sluggish MOR. These novel Pt/Ni(OH)2/NG catalysts exhibit an excellent mass activity of 2.99 A mg⁻¹Pt for methanol electrooxidation, which is about 2.8 and 4.8 times higher than those of commercial PtRu/C and Pt/C, respectively. Furthermore, both durability and CO tolerance of Pt/Ni(OH)2/NGs electrocatalysts are significantly improved.
Reactions of SnX2 (X = Cl, Br) with [PtMe2(bipy)], 1, (bipy = 2,2'-bipyridine), followed by NaBH4 reduction at toluene/water interface, in the presence or absence of graphene oxide support, rendered PtSn nanoalloy thin films. They were characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The electrocatalytical activity of the PtSn thin films was investigated in the methanol oxidation reaction (MOR). Our studies showed that the PtSn/reduced-graphene oxide (RGO) thin film gave better catalytic results for MOR in comparison to bare PtSn or Pt thin films. A maximum jf/jb ratio (jf and jb are the maximum current densities in the forward and backward scans, respectively) of 6.77 was obtained for the PtSn/RGO thin film deriving from the 1 + SnBr2 + NaBH4 sequence.
Concave nanostructures with the high-index facets and highly exposed active sites are desirable in energy conversion technology, whereas the current synthetic strategies still remain challenging. Herein, we report a facile and effective strategy for the synthesis of concave PtCo nanocrosses (PtCo CNCs) with the assist of iminodiacetic acid (IDA). Owing to strong chelation of IDA with metal ions through carboxyl and imino groups, the IDA molecule plays a key role as the structure-directing agent in regulating the cross-like structure. The as-prepared PtCo CNCs are constructed by six arms in three-dimensional space and each protruding arm has concave surface bounded by high-index facets. As an electrocatalyst towards methanol oxidation reaction (MOR), the developed PtCo CNCs exhibit much enhanced specific and mass activity of 3.04 mA cmPt⁻² and 692 mA mgPt⁻¹ that are 3.1 and 2.6 times greater than those of commercial Pt black, respectively. The excellent electrocatalytic stability and improved tolerance toward COads are also demonstrated on PtCo CNCs catalyst. The remarkable electrocatalytic performance of PtCo CNCs towards MOR is highly related with their concave surface and high-index facets, as well as synergistic effect between Pt and Co atoms. The facile synthetic strategy and outstanding MOR performance endow PtCo CNCs with great application potential in fuel cells as an anode catalyst.
The improvement of performance for Pt-based electrocatalysts is of significant importance. Here we synthesized a Ce-modified Pt nanoparticle (NP) with Cerium (III) oxygenated species (1 wt% Ce content) anchored on Pt NPs for methanol oxidation reaction (MOR). High-angle annular dark field-scanning transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption fine structure spectroscopy were combined to prove and analyze this special structure. Surprisingly, the electrocatalytic activity of the Ce-modified Pt NPs for MOR reached 1470 mA/mg-Pt and 8670 mA/mg-Pt in acidic and alkaline media, respectively, which were superior to those of the Pt NPs/C and commercial Pt/C. Density functional calculations showed that the structure of Pt surface was deformed by the modification of Cerium, which made CO* + OH* bind more strongly, and the stronger anchoring of OH* induced the easier removal of CO* in the potential determining step. This work would provide an effective strategy to develop efficient MOR electrocatalysts.
Inferior stability and anti-poisoning capacity of Pt-based ultrathin nanowires (NWs) are critical weaknesses under detrimental acidic running conditions for proton-exchange membrane fuel cell applications due to their energetic surface. Here 1.5-nm-thin quatermetallic PtCoNiRh NWs with high atomic-exposure are fabricated to serve as robust electrocatalysts for acidic methanol oxidation reaction (MOR). Surpassing Rh-free PtCoNi NWs and most of state-of-the-art catalysts, the PtCoNiRh NWs achieve extremely high MOR activity (1.36 A·mg⁻¹Pt and 2.08 mA·cm⁻²) with substantially lowered onset-potential and improved CO-tolerance. The anticorrosion effect of incorporated-Rh can effectively stabilize the PtCoNiRh NWs in the corrosive MOR. Electrochemical in situ Fourier transform infrared spectroscopy and density functional theory simulation cooperatively reveal that the methanol dehydrogenation is inclined to occur at the interatomic Pt–Rh sites, where the intermediate COads prefers bridge binding mode rather than linear mode with facilitated removal. Integratedly, the complete 6e⁻-transferred MOR process is reliably accelerated and stays efficient on the quaternary PtCoNiRh NWs.
The design of electrocatalysts with high activity and enhanced durability for ethanol oxidation reaction (EOR) is critical for commercializing the direct ethanol fuel cells (DEFCs). Herein, a distinct class of one-dimensional (1D) ultrathin Pt3Sn nanofibers (NFs) with controllable aspect ratios and intermetallic structure were designed as highly efficient EOR electrocatalysts. The optimized structurally ordered Pt3Sn NFs with the largest aspect ratio (Pt3Sn NFs-L) show the highest activity and long-term stability compared with the commercial Pt/C and other counterparts. Apart from the intrinsic structure advantages, the incorporated Sn on Pt3Sn NFs-L can effectively alleviate the binding strength of reaction intermediates and further promote the intermediates electrooxidation by providing abundant oxophilic species, largely contributing to the enhanced EOR activity and stability. Detailed investigations indicate that the Pt3Sn NFs-L possesses strong capacity for C-C bond cleavage in ethanol, leading to the enhanced catalytic activity. Moreover, the Pt3Sn NFs-L with highlighted anti-poisoning property can also display enhanced performances for ethylene glycol oxidation reaction (EGOR) and glycerol oxidation reaction (GOR), demonstrating their promising performances for various alcohol electrooxidation reactions.
Pt-based alloy catalysts are promising candidates for fuel cell applications, especially for cathodic oxygen reduction reaction (ORR) and anodic methanol oxidation reaction (MOR). Rational design of composition and morphology is crucial to promoting the catalytic performances. Here, we report the synthesis of Pt−Co nanoframes via chemical etching of Co from solid rhombic dodecahedra. The obtained Pt−Co nanoframes exhibit remarkable ORR and MOR properties. The ORR mass activity in acidic electrolyte is as high as 0.40 A mgPt⁻¹ at 0.95 VRHE, which is 4 times higher than that of commercial Pt/C catalyst. The long-term ORR durability also stands out with 0.34 A mgPt⁻¹ maintained after 10,000 potential cycles, accredited to negligible Co dissolution. Furthermore, the MOR mass activity of the nanoframes in alkaline media is up to 4.28 A mgPt⁻¹, which is 4-fold enhancement compared with that of commercial Pt/C. Experimental studies indicate that the weakened binding of intermediate carbonaceous poison contributes to the enhanced MOR activity. More impressively, the Pt−Co nanoframes also show remarkable structural stability after the electrocatalysis. This work provides an effective strategy to produce high-performance Pt−Co nanoframes for fuel-cell-related applications.
Improving the electrocatalytic activity and durability of electrocatalysts is of vital importance to the direct methanol fuel cells. PtRu materials are the most effective catalysts for methanol oxidation reaction (MOR) in acidic medium, but it still exhibits partial defects, such as limited catalytic activity. Here we prepared a series of surface oxygen-mediated ultrathin PtRuM (M = Ni, Fe, and Co) nanowires (NWs), termed PtRuM-O. All these prepared materials show ultrahigh electrocatalytic activity and excellent durability for MOR in acidic medium due to the optimal electronic structures induced by the introduction of electroactive O. Until now, in the reported Pt-based materials article (Table S1), the optimal Pt62Ru18Ni20-O/C electrocatalyst shows the highest mass activity of 2.72 A mg−1pt for MOR in the acidic medium, which is 1.42, 5.14 and 9 times higher than that of Pt62Ru18Ni20/C (1.91 A mg−1pt), Pt65Ru35/C (0.47 A mg−1pt) and Pt/C (0.30 A mg−1pt) NWs catalysts, respectively. And the Pt62Ru18Ni20-O/C catalyst still retains 92% of initial mass activity after 1000 cyclic voltammetry (CV). The CO stripping experiment results reveal that the peak potential of Pt62Ru18Ni20-O/C show a negative shift compare with Pt62Ru18Ni20/C, Pt65Ru35/C, and Pt/C NWs catalysts, indicating that the Pt62Ru18Ni20-O/C catalyst has the best CO anti-poisoning. The prepared electrocatalysts also show better MOR performance in the alkaline medium. Density functional theory (DFT) calculations prove that the introduction of O to PtRuNi significantly boosts the MOR performance by strengthening the adsorption of initial CH3OH induced by the electroactive O-2p bands. Meanwhile, the much larger energy barrier for CO generation indicates the much lower probability of catalyst poisoning of the PtRuNi-O.
PtRu bimetal is of particularly attractive in various electrocatalytic reactions owing to its synergistic effect, ligand effect and strain effect. Here, PtRu nanoalloy supported on porous graphitic carbon (PC) has been successfully prepared via a very facile method involving co-reduction the precursors of Pt and Ru at 300 °C by H2 (PtRu/PCL) followed by thermal treatment at high temperature (700 °C, PtRu/PC–H). Specifically, the electrocatalytic performance of PtRu/PC nanoalloy could be dramatically enhanced through high-temperature annealing. This strategy has synthesized smaller Pt and PtRu nanoparticles (ca. < 3 nm); what's more, they are all homogeneous deposited on the surface of PC. PtRu/PC–H nanocatalyst displays higher alloying degree and stronger electronic interaction between Pt and Ru atoms accompanied by the downshift of Pt d-band center. Studies of electrochemical tests indicate that the as-fabricated PtRu/PC–H sample exhibits superior electrocatalytic performance and excellent CO-poisoning tolerance compared with PtRu/PCL and Pt/PC nanocatalysts. The mass activity and specific activity on PtRu/PC–H nanoalloy can be increased to 1674.2 mA mg⁻¹Pt and 4.4 mA cm⁻² for MOR, it is 4.08 and 8.80 times higher than that of the Pt/PC nanocatalyst, respectively. From in-situ FTIR spectra, we can discover PtRu/PC–H nanoalloy generates CO2 at a lower potential of −150 mV than those on PtRu/PC–L (0 mV) and Pt/PC (50 mV) nanocatalysts, dramatically improves the ability of cleavage C–H bond and alleviates the COads poisoning on active sites. The PtRu/PCH nanocatalyst exhibits maximum power density of 83.7 mW cm⁻² in single methanol fuel cell test, which more than threefold than that of commercial Pt/C as the anode catalyst. Those experimental results open an effective and clean avenue in the development and preparation of high-performance Pt-based nanocatalysts for direct methanol fuel cells.
Owing to their intrinsically high activity and rich active sites on the surface, noble metal materials with ultrathin 2D nanosheet structure are emerging as ideal catalysts for boosting fuel cell reactions. However, the realization of controllable synthesis of multimetallic Pd-based alloy ultrathin nanosheets (NSs) for achieving enhanced electrocatalysis evolved from compositional and structural advantages remains a grand challenge. Herein, we report a universal method for the construction of a new series of 3D multimetallic PdCuM (M= Ru, Rh, Ir) superstructure that consists of ultrathin alloy NSs. Different from the conventional 2D ultrathin nanostructure. The 3D PdCuM NSs that endowed with abundant routes for fast mass transport, high noble material utilization efficiency, ligand effect from M to PdCu display large promotion in electrocatalytic performance for methanol oxidation reaction (MOR). Impressively, the composition-optimized Pd59Cu33Ru8 NSs, Pd57Cu34Rh9 NSs, and Pd63Cu29Ir8 NSs show the mass activities of 1660.8, 1184.4, and 1554.8 mA mg⁻¹ in alkaline media, which are 4.9, 4.6, and 3.5-fold larger than that of commercial Pd/C, respectively. More importantly, all of the PdCuM NSs are also very stable for long-term electrochemical tests.
The development of cost-effective methanol oxidation reaction (MOR) catalysts with a high activity and stability is highly desirable for direct methanol fuel cells. In this study, the structurally ordered PtSn intermetallic nanoparticles supported on Sb-doped SnO2 (ATO) have been successfully synthesized in ethylene glycol (EG) solution at 200 oC. The Pt NPs were firstly formed on ATO, followed by the transformation from Pt to hexagonal PtSn on the surface of ATO. The obtained structurally ordered PtSn intermetallic NPs supported on ATO demonstrate significantly enhanced MOR activity and durability in comparison with commercial Pt/C. Our PtSn intermetallic NPs supported on ATO show a MOR activity 4.1 times higher than that of the commercial Pt/C catalyst. Accelerated durability tests indicate that the commercial Pt/C catalyst loses about 50% of its initial current density after 500 cycles while only about 15% loss of its initial current density for the Pt/ATO-200-3h catalyst. Our PtSn intermetallic NPs supported on ATO are also found to have higher CO tolerance than the commercial Pt/C. This work demonstrates an important strategy to rationally design high performance of structurally ordered Pt-based intermetallic NPs catalysts for fuel cell and other applications.
Noble metal binary and ternary catalysts have become a new class of fuel cell electrocatalysts due to their high catalytic activity. However, improvement is still necessary to reduce the consumption of Pt and obtain the quaternary Pt-based catalyst by Mo modification. Through the introduction of Mo(CO)6, novel quaternary hexapod nano-skeletons with high-index facets are obtained here, which are composed of core, first-layer feet and second-layer feet. Compared with PtCoNi nano-particles (NPs), the vertex-reinforced PtCoNiMo hexapod nano-skeletons (NSs), due to abundant tip areas, can facilitate electron transfer and mass exchange. It is found that the as prepared PtCoNiMo nano-skeletons catalyst exhibits enhanced mass activity, stability and anti-poisoning ability towards methanol oxidation reaction and oxygen reduction reaction, compared to commercial Pt/C catalyst and PtCoNi nanoparticles. More importantly, the development of quaternary catalysts can create better possibilities for the performance improvement of Pt-based catalysts.
A current challenge to direct methanol fuel cells (DMFCs) is the insufficient electrocatalytic activity and anti-CO poisoning ability of Pt-based alloy catalysts toward the methanol oxidation reaction (MOR). In this work, a simple thermally driven interfacial diffusion alloying method is adopted to synthesize the Pt3CoRu/C@NC trimetallic nanoparticles (NPs) with enhanced MOR activity and anti-CO poisoning ability. The MOR mass activity of the Pt3CoRu/C@NC (0.97 mA/ugPt) catalyst exhibits 4.2 times larger than that of the commercial Pt/C (0.23 mA/ugPt) catalyst. Moreover, the Pt3CoRu/C@NC catalyst exhibit much lower CO oxidation onset potential than the commercial Pt/C catalyst (0.35V vs 0.82V), which directly indicates the improved anti-CO poisoning ability of the catalyst. This enhancement in MOR activity as well as anti-CO poisoning ability of the Pt3CoRu/C@NC catalyst is mainly attributed to the synergistic effect of Ru (as water activator) and Co (as an electronic modifier). Indeed, this work not only provides a satisfactory strategy for improving the activity and anti-CO poisoning ability of the MOR electrocatalysts but also gives a significant insight into the simple and cost-effective alloying methods for developing homogeneously trimetallic alloy catalysts.
Pt-based catalysts for the methanol fuel electroxidation typically suffer from the CO intermediate poisoning. Herein, we incorporated secondary Ni element into PtPd hollow nanocrystals (HNCs) to fabricate trimetallic NiPtPd-HNCs catalyst with superior CO tolerance and high activity for methanol electro-oxidation. The as-prepared trimetallic NiPtPd-HNCs exhibited a promising specific and mass activity of 10.68 mA•cm−2 and 3.95 A•mgPd+Pt−1, respectively, which is 4.2- and 4.5-fold higher than that of commercial Pt/C. Notably, CO-stripping tests and 3000 s chronoamperometry experiments in a rigorous CO-saturated medium show that trimetallic NiPtPd-HNCs possess higher CO tolerance compared with that of the bimetallic counterparts. Ultimately, we ascribed to the enhanced activity and CO tolerance of trimetallic NiPtPd-HNCs to: (i) the preponderance of hollow interior and dendritic morphology, (ii) the considerably improved binding energy of OHads on NiPtPd surface which is beneficial to the removal of the partial oxidation intermediates during the methanol electro-oxidation; (iii) the modification of the electronic structure of Pt and Pd caused by Ni heteroatoms exposure to surface. The employment of Ni may be extended to the rational development of other Pt-based multimetallic nanocrystals with high CO tolerance and promising activity in the small molecules fuel electroxidation.
Sub-1 nm PtSn nanosheets of 0.6–0.9 nm in thickness were synthesized via a solution colloidal method and were applied as electrooxidation catalysts for methanol oxidation reaction (MOR) and ethanol oxidation (EOR) in alkaline and acid environments. Owing to the specific structural and compositional characteristics, the as-prepared PtSn nanosheets exhibits superior activity and durability relative to commercial Pt black and Pt/carbon catalysts. PtSn nanosheets not only exhibit an outstanding mass activity in MOR (871.6 mA mg Pt ⁻¹ ), which is 2.3 times (371 mA mg Pt ⁻¹ ) and 10.1 times (86.1 mA mg Pt ⁻¹ ) higher than that of commercial Pt/carbon and Pt black respectively, but also display an mass activity in EOR (673.6 mA mg Pt ⁻¹ ) with 5.3 times higher commercial Pt black (127.7 mA mg Pt ⁻¹ ) and 2.3 times higher than commercial Pt/C catalyst (295 mA mgPt ⁻¹ ). The reported value is the highest activity in both MOR and EOR examinations compared to the reported PtSn-based electrocatalysts,. The improved performance may be due to the highly-reactive exposed (1 1 1) facet sites resulted from its sub-1 nm 2D sheet like morphology.
The ethanol oxidation reaction is extensively explored, but electrocatalysts that could achieve complete oxidation pathway to CO2/CO32- are very less reported. Here, we synthesize the monatomic Pt layer (Pt-skin) on ordered intermetallic PtBi clusters (PtBi@Pt) supported on graphene via a single atoms self-assembling (SAS) method to form a superior catalyst. The PtBi@Pt with ultrafine size (~2 nm) delivers an extremely high mass activity of 9.01 mA gPt-1, which is 8-fold more active than commercial Pt/C; significantly, in-situ Fourier transform infrared spectroscopy indicates that ethanol is completely oxidized to CO32- on the PtBi@Pt, accompanied by 12 electron transfer, as is further demonstrated by the density functional theory results.
Direct ethanol fuel cells (DEFC) are one of the most promising electrochemical energy conversion devices for portable, mobile and stationary power applications. However, more efficient and stable and less expensive electrocatalysts are still required. Interestingly, the electrochemical performance of the electrocatalysts towards the ethanol oxidation reaction (EOR) can be remarkably enhanced by exploiting the benefits of structural and compositional sensitivity and control. Here we describe the synthesis, characterization and electrochemical behavior of cubic Pt-Sn nanoparticles. The electrochemical activity of the cubic Pt-Sn nanoparticles was found to be about three times higher than that obtained with unshaped Pt-Sn nanoparticles and six times higher than that of Pt nanocubes. In addition, stability tests indicated the electrocatalyst preserves its morphology and remains well-dispersed on the carbon support after 5,000 potential cycles, while a cubic (pure) Pt catalyst exhibited severe agglomeration of the nanoparticles after a similar stability testing protocol. A detailed analysis of the elemental distribution in the nanoparticles by STEM-EELS indicated that Sn dissolves from the outer part of the shell after potential cycling, forming a ~0.5 nm Pt skin. This particular atomic composition profile having a Pt-rich core, a Sn-rich subsurface layer and a Pt-skin surface architecture is responsible of the high activity and stability.
Highly ordered hierarchical Pt and PtNi nanowire arrays were prepared by using CdS hierarchical nanowire arrays (HNWAs) as sacrificial templates and demonstrated high electrochemical active surface areas. For the resulting Pt HNWAs sample, the peak current for methanol oxidation at +0.74 V was almost one order of magnitude higher than that of Pt solid nanowire arrays (SNWAs) prepared in a similar manner but without the use of CdS template, and the addition of a Ni cocatalyst effectively enhanced the tolerance against CO poisoning. The results demonstrated that highly ordered Pt and PtNi HNWAs may be exploited as promising anode catalysts in the application of direct methanol fuel cells.
Despite that both electrochemical experiments and density functional theory calculations have testified the superior electrocatalytic activity and CO-poisoning tolerance of platinum-ruthenium (PtRu) alloy nanoparticles toward the methanol oxidation reaction (MOR), the facet-dependent electrocatalytic properties of PtRu nanoparticles are scarcely revealed because it is extremely difficult to synthesize well-defined facets enclosed PtRu nanocrystals. Herein, we for the first report a general synthesis of ultrathin PtRu nanocrystals with tuneable morphologies (nanowires, nanorods and nanocubes) through a one-step solvothermal approach, and systematically investigate the structure-directing effects of different surfactants and the formation mechanism by control experiments and time-dependent studies. In addition, we utilize these {100} and {111} facets enclosed PtRu nanocrystals as model catalysts to evaluate the electrocatalytic characteristics of MOR on different facets. Remarkably, the {111}-terminated PtRu nanowires exhibit much higher stability and electrocatalytic mass activity toward MOR, which are 2.28- and 4.32-times higher than {100}-terminated PtRu nanocubes and commercial Pt/C, respectively, indicating that PtRu {111} facets possess superior methanol oxidation activity and CO-poisoning resistance of relative to {100} facets. Our present work provides a series of well-defined PtRu nanocrystals with tuneable facets, which would be ideal model electrocatalysts for fundamental research of fuel cell electrocatalysis.
Five-fold-twinned PtCu nanoframes (NFs) with nanothorns protruding from their edges have been synthesized by a facile one-pot method. Compared to commercial Pt/C catalyst, the obtained highly anisotropic five-fold-twinned PtCu NFs show enhanced electrocatalytic performance toward the oxygen reduction reaction and methanol oxidation reaction under alkaline conditions.
Introducing high-index facets into nanocrystals (NCs) is an effective way for boosting the electrocatalytic intrinsic activity. However, the established NCs with high-index facets usually have big diameter, which makes them exhibit very limited surface area, thus finally limited mass activity. To well embody the advantage of high-index facets in enhancing electrocatalysis, the better nanostructures should meet the requirement of both high surface area and high-density high-index facets. Herein, we report our important advances in making the unique three-dimensional screw thread-like platinum-copper (Pt-Cu) alloy nanowires (NWs) with high-density high-index facets and controlled composition. Such special NWs with high surface area of 46.90 m2g-1 exhibit much better performance than the PtCu nanoparticles (NPs) in alcohol electrooxidations. This work opens a new way for maximizing the electrocatalytic performance by introducing high-index facets into high-surface-area stable bimetallic NWs.
Excavated polyhedral noble-metal materials that were built by the orderly assembly of ultrathin nanosheets have both large surface areas and well-defined facets, and therefore could be promising candidates for diverse important applications. In this work, excavated cubic Pt-Sn alloy nanocrystals (NCs) with {110} facets were constructed from twelve nanosheets by a simple co-reduction method with the assistance of the surface regulator polyvinylpyrrolidone. The specific surface area of the excavated cubic Pt-Sn NCs is comparable to that of commercial Pt black despite their larger particle size. The excavated cubic Pt-Sn NCs exhibited superior electrocatalytic activity in terms of both the specific area current density and the mass current density towards methanol oxidation.
Methanol is a promising fuel for direct methanol fuel cells in portable devices. A deeper understanding of its electro-oxidation is needed for evaluating electrocatalytic performance and catalyst design. Here we provide an in-depth investigation of the cyclic voltammetry (CV) of methanol electro-oxidation. The oxidation peak in backward scan is shown to be unrelated to residual intermediate oxidation. The origin of the second oxidation peak (If2) is expected to the methanol oxidation on Pt-Ox. Electrochemical impedance spectroscopy coupled with CV reveals the origin of CV hysteresis to be a shift in the rate-determining step, from methanol dehydration to OH adsorption by water dissociation, induced by a change in Pt surface coverage with oxygenated species. The peak ratio between forward oxidation peak current (If) and backward oxidation peak current (Ib), which is If/Ib, is not related to the degree of CO tolerance but to the degree of oxophilicity indeed.
