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![DFT calculations. Calculated density of states and crystal structure of (a) the reconstructed surface of bulk WO 3 , (b) the Pt nanoparticles on reconstructed surface of Pt/WO 3 , (c) the W-terminated surface of ultrathin WO 3-Ar nanosheets, and (d) the Pt nanoparticles on W-terminated surface of Pt/WO 3-Ar along the [001] orientation.](profile/Yiqiong-Zhang-5/publication/328383396/figure/fig4/AS:685212686090241@1540378843923/DFT-calculations-Calculated-density-of-states-and-crystal-structure-of-a-the.png)
DFT calculations. Calculated density of states and crystal structure of (a) the reconstructed surface of bulk WO 3 , (b) the Pt nanoparticles on reconstructed surface of Pt/WO 3 , (c) the W-terminated surface of ultrathin WO 3-Ar nanosheets, and (d) the Pt nanoparticles on W-terminated surface of Pt/WO 3-Ar along the [001] orientation.
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Proper design of support materials is an important approach to improve the utilization efficiency and regulate the electronic properties of Pt electrocatalysts. Herein, we have successfully prepared ultrathin WO3 nanosheets...
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Context 1
... WO 3 surface, while 2.1 electrons transfer in opposite direction from W-terminated surface to Pt nanoparticles, indicating the strong metal-support interactions between Pt and WO 3 with Vo. Moreover, it is well known that charge redistribution is accompanied by alteration of frontier orbit which directly involves surface reactions. As shown in Fig. 6b, d, comparing with the density of state (DOS) of Pt nanoparticles on two substrates, Pt on W-terminated surface have dense DOS around the Fermi level, which shows more high-activity electrons can be supplied. Pt on reconstructed surface contribute more deep energy levels due to strong binding between single-coordinated surface O atoms. To ...
Citations
... In particular, in contrast to bulk WO 3 , two-dimensional (2D) WO 3 nanosheets have been found to exhibit enhanced optical contrast and durability due to the expanded active surface area and facilitated ion penetration within EC materials [10,11]. Various techniques are used to produce 2D WO 3 materials, achievable through two synthetic strategies: the top-down and the bottom-up approach [10,[12][13][14][15][16][17]. The bottom-up methods aim to produce 2D WO 3 from smaller precursor molecules, whereas the top-down approach involves the direct exfoliation of bulk precursors. ...
... Only a few studies on the production of ultrathin 2D WO 3 nanosheets with liquid-phase exfoliation have been reported to date. This can be achieved through methods such as the direct exfoliation of bulk WO 3 , exfoliation and oxidation from tungsten disulfide (WS 2 ), and the exfoliation of hydrated WO 3 [11,15,16,18,19]. Guan et al. achieved the direct exfoliation of WO 3 powder into thin nanosheets by coating the surface of WO 3 with bovine serum albumin (BSA) [18]. ...
... Subsequent investigations aimed to generate WO 3 intercalation compounds with the goal of producing WO 3 nanosheets without the need for additional oxidation processes. The layered WO 3 hydrates can serve as effective precursors for the preparation of ultrathin WO 3 nanosheets [15,16,20]. Hydrated WO 3 is typically manufactured on a nanometer scale, resulting in exfoliated nanosheets with small lateral sizes (less than 500 nm). ...
It is difficult to obtain ultrathin two-dimensional (2D) tungsten trioxide (WO3) nanosheets through direct exfoliation from bulk WO3 in solution due to the strong bonding between interlayers. Herein, WO3 nanosheets with controllable sizes were synthesized via K+ intercalation and the exfoliation of WO3 powder using sonication and temperature. Because of the intercalation and expansion in the interlayer distance, the intercalated WO3 could be successfully exfoliated to produce a large quantity of individual 2D WO3 nanosheets in N-methyl-2-pyrrolidone under sonication. The exfoliated ultrathin WO3 nanosheets exhibited better electrochromic performance in an electrochromic device than WO3 powder and exfoliated WO3 without intercalation. In particular, the prepared small WO3 nanosheets exhibited excellent electrochromic properties with a large optical modulation of 41.78% at 700 nm and fast switching behavior times of 9.2 s for bleaching and 10.5 s for coloring. Furthermore, after 1000 cycles, the small WO3 nanosheets still maintained 86% of their initial performance.
... The defect theory indicates the center of defect sites has high binding energy with metal ions, which can effectively act as the adsorption center of metal ions and inhibit their migration and aggregation during the doping process. Zhang et al. 40 reported that the oxygen vacancies in WO 3 can serve as efficient anchoring sites and inhibit the aggregation of Pt atoms. Li et al. 41 also anchored Pt atoms on the MoO 2 nanosheets with oxygen vacancies as nucleation sites. ...
Abstract Heteroatomic substitution and vacancy engineering of spinel oxides can theoretically optimize the oxygen evolution reaction (OER) through charge redistribution and d‐band center modification but still remain a great challenge in both the preparation and catalytic mechanism. Herein, we proposed a novel and efficient Ar‐plasma (P)‐assisted strategy to construct heteroatom Mo‐substituted and oxygen vacancies enriched hierarchical spinel Co3O4 porous nanoneedle arrays in situ grown on carbon cloth (denoted P‐Mo‐Co3O4@CC) to improve the OER performance. Ar‐plasma technology can efficiently generate vacancy sites at the surface of hydroxide, which induces the anchoring of Mo anion salts through electrostatic interaction, finally facilitating the substitution of Mo atoms and the formation of oxygen vacancies on the Co3O4 surface. The P‐Mo‐Co3O4@CC affords a low overpotential of only 276 mV at 10 mA cm−2 for the OER, which is 58 mV superior to that of Mo‐free Co3O4@CC and surpasses commercial RuO2 catalyst. The robust stability and satisfactory selectivity (nearly 100% Faradic efficiency) of P‐Mo‐Co3O4@CC for the OER are also demonstrated. Theoretical studies demonstrate that Mo with variable valance states can efficiently regulates the atomic ratio of Co3+/Co2+ and increases the number of oxygen vacancies, thereby inducing charge redistribution and tuning the d‐band center of Co3O4, which improve the adsorption energy of oxygen intermediates (e.g., *OOH) on P‐Mo‐Co3O4@CC during OER. Furthermore, the two‐electrode OER//HER electrolyzer equipped with P‐Mo‐Co3O4@CC as anode displays a low operation potential of 1.54 V to deliver a current density of 10 mA cm−2, and also exhibits good reversibility and anticurrent fluctuation ability under simulated real energy supply conditions, demonstrating the great potential of P‐Mo‐Co3O4@CC in water electrolysis.
... The electrochemical behaviors of HEA-400, HEA-700 and Pt/C catalysts were measured (Fig. 3a) by cyclic voltammetry (CV). The reduction peak potential for Pt-OH ad of HEA-700 is shifted forward compared with those of HEA-400 and Pt/C, which indicates HEA-700 has the weakest adsorption for oxygen-containing species [46]. Combining ECSA and ICP-OES analyses (Tables S4 and S5), as displayed in Fig. 3b, HEA-400 (Fig. 3c) and higher than most of the state-of-the-art catalysts in recent reports (Table S6). ...
... The high activity is partly caused by different surface compressive strain between them. As another important index, the ratio of peak current density of the forward-to-backward scans (I f /I b ) can be applied to evaluate the tolerance of electrocatalysts to the poisoning of intermediate carbonaceous species in MOR [46,47]. The ratio (Fig. S8) indicates that HEA-700 (I f /I b = 1.21) has better poisoning tolerance than HEA-400 (I f /I b = 1.09) and Pt/C (I f /I b = 0.58). ...
High-entropy alloys (HEAs) have been widely studied due to their unconventional compositions and unique physicochemical properties for various applications. Herein, for the first time, we propose a surface strain strategy to tune the electrocatalytic activity of HEAs for methanol oxidation reaction (MOR). High-resolution aberration-corrected scanning transmission electron microscopy (STEM) and elemental mapping demonstrate both uniform atomic dispersion and the formation of a face-centered cubic (FCC) crystalline structure in PtFeCoNiCu HEAs. The HEAs obtained by heat treatment at 700°C (HEA-700) exhibit 0.94% compressive strain compared with that obtained at 400°C (HEA-400). As expected, the specific activity and mass activity of HEA-700 is higher than that of HEA-400 and most of the state-of-the-art catalysts. The enhanced MOR activity can be attributed to a shorter Pt-Pt bond distance in HEA-700 resulting from compressive strain. The nonprecious metal atoms in the core could generate compressive strain and down shift d-band centers via electron transfer to surface Pt layer. This work presents a new perspective for the design of high-performance HEAs electrocatalysts.
... (2) The charge transfer between Fe x N nanoparticles and RGO will enhance the oxygen adsorption and boost the catalytic activity of ORR [50]. (3) The evenly distributed Fe x N nanoparticles prevent the stacking of RGO, which guarantee the high specific surface area and pore volume, strengthen the exchange interaction between oxygen and catalytic active site, and provide large electrode-electrolyte interfaces for improving the catalytic activity [51,52]. (4) Although FGN-8 has the lowest Fe content from the above XPS analysis, the successful transformation from Fe 3 O 4 and Fe 2 N to Fe 3 N guarantees the high electrocatalytic performance. ...
... In addition to the performance in alkaline media, the performance in acidic media is another major challenge for industrial application. In this study, the electrocatalytic activities of commercial Pt/C and FGN ECSA is another important index to evaluate the stability of catalytic activity [52,54,55]. The CV after long circulation can be used to evaluate the durability of commercial Pt/C and FGN-8 catalysts, with a scan rate of 50 mV s −1 in O 2 -saturated 0.5 M H 2 SO 4 at room temperature. ...
Although Fe–N/C catalysts have received increasing attention in recent years for oxygen reduction reaction (ORR), it is still challenging to precisely control the active sites during the preparation. Herein, we report FexN@RGO catalysts with the size of 2–6 nm derived from the pyrolysis of graphene oxide and 1,1′-diacetylferrocene as C and Fe precursors under the NH3/Ar atmosphere as N source. The 1,1′-diacetylferrocene transforms to Fe3O4 at 600°C and transforms to Fe3N and Fe2N at 700°C and 800°C, respectively. The as-prepared FexN@RGO catalysts exhibited superior electrocatalytic activities in acidic and alkaline media compared with the commercial 10% Pt/C, in terms of electrochemical surface area, onset potential, half-wave potential, number of electrons transferred, kinetic current density, and exchange current density. In addition, the stability of FGN-8 also outperformed commercial 10% Pt/C after 10000 cycles, which demonstrates the as-prepared FexN@RGO as durable and active ORR catalysts in acidic media.
... These catalysts merged the advantages of metal active sites as well as oxygen vacancy and further their morphologies can be controlled to tune their catalytic activity [29,30]. At present, there has been a lot of scientific research showing that vacancy engineering can reduce the energy barrier of the oxygen evolution reaction (OER) to reduce the potential, especially in the NRR to selectively inhibit the hydrogen evolution reaction participating in the competition [31][32][33]. Similar to the classic electrocatalytic total water splitting reaction, the efficiency of electrocatalytic NRR reaction can be improved by increasing the activity and number of active sites of the catalyst. ...
In order to sustainably transform N2 to ammonia (NRR) using electrocatalysts under mild ambient condition, it is urgent to design and develop non-nobel metal nanocatalysts that are inexpensive and suitable for mass-production. Herein, a calcium metalate catalyst CaCoOx with oxygen vacancies was synthesized and used as an electrocatalyst for NRR for the first time, whose morphology can be controlled by the calcination temperature and the heating rate. Under the optimal conditions, the CaCoOx catalyst achieved the yield of nitrogen conversion to ammonia of 16.25 µg·h−1·mgcat−1 at the potential of −0.3 V relative to the reversible hydrogen electrode (RHE) with a Faraday efficiency of 20.51%. The electrocatalyst showed good stability even after 12 times recyclability under environmental conditions and neutral electrolyte. Later, the electrocatalytic nitrogen reduction performance of CaFeOx, CaNiOx, CaCuOx was investigated. These earth-rich transition metals also exhibited certain NRR electrocatalytic capabilities, which provided a door for further development of inexpensive and easily available transition metal as nitrogen reduction electrocatalysts.
... For instance, utilizing the Ar plasma exfoliation technique, Zhang and colleagues prepared Pt nanoparticles-loaded ultrathin WO 3 nanosheets, which exhibited enriched oxygen vacancies and increased electrical conductivity, as remarkable electrocatalysts towards MOR [121]. From Fig. 6a, the agglomerated Pt nanoparticles can be seen to exhibit an average particle size of 3.34 nm. ...
... (i) CV curves of the as-prepared catalysts in N 2 -saturated 1.0 M KOH + 1.0 M ethanol solution at the scan rate of 50 mV s −1 .(a-c) Reproduced from Ref.[121] with permission from The Royal Society of Chemistry. (d, e) Reprinted from Ref.[126]. ...
Transition metal borides, carbides, pnictides, and chalcogenides (X-ides) have emerged as a class of materials for the oxygen evolution reaction (OER). Because of their high earth abundance, electrical conductivity, and OER performance, these electrocatalysts have the potential to enable the practical application of green energy conversion and storage. Under OER potentials, X-ide electrocatalysts demonstrate various degrees of oxidation resistance due to their differences in chemical composition, crystal structure, and morphology. Depending on their resistance to oxidation, these catalysts will fall into one of three post-OER electrocatalyst categories: fully oxidized oxide/(oxy)hydroxide material, partially oxidized core@shell structure, and unoxidized material. In the past ten years (from 2013 to 2022), over 890 peer-reviewed research papers have focused on X-ide OER electrocatalysts. Previous review papers have provided limited conclusions and have omitted the significance of “catalytically active sites/species/phases” in X-ide OER electrocatalysts. In this review, a comprehensive summary of (i) experimental parameters (e.g., substrates, electrocatalyst loading amounts, geometric overpotentials, Tafel slopes, etc.) and (ii) electrochemical stability tests and post-analyses in X-ide OER electrocatalyst publications from 2013 to 2022 is provided. Both mono and polyanion X-ides are discussed and classified with respect to their material transformation during the OER. Special analytical techniques employed to study X-ide reconstruction are also evaluated. Additionally, future challenges and questions yet to be answered are provided in each section. This review aims to provide researchers with a toolkit to approach X-ide OER electrocatalyst research and to showcase necessary avenues for future investigation.
Transition-metal-based layered double hydroxides (TM-LDHs) nanosheets are promising electrocatalysts in the renewable electrochemical energy conversion system, which are regarded as alternatives to noble metal-based materials. In this review, recent advances on effective and facile strategies to rationally design TM-LDHs nanosheets as electrocatalysts, such as increasing the number of active sties, improving the utilization of active sites (atomic-scale catalysts), modulating the electron configurations, and controlling the lattice facets, are summarized and compared. Then, the utilization of these fabricated TM-LDHs nanosheets for oxygen evolution reaction, hydrogen evolution reaction, urea oxidation reaction, nitrogen reduction reaction, small molecule oxidations, and biomass derivatives upgrading is articulated through systematically discussing the corresponding fundamental design principles and reaction mechanism. Finally, the existing challenges in increasing the density of catalytically active sites and future prospects of TM-LDHs nanosheets-based electrocatalysts in each application are also commented.
