Figure 5 - uploaded by Jianshuo Zhang
Content may be subject to copyright.
(a) Polarization and power density curves of the Zn−air batteries with MnO 2 /N-HGS (red lines) and Pt/C (black lines) as catalysts. (b) The galvanostatic discharge curves of a Zn−air battery with MnO 2 /N-HGS as catalysts at various current densities (5, 10, and 25 mA cm −2 ). (c) Long-term galvanostatic discharge curves of Zn−air batteries with MnO 2 /N-HGS and Pt/C catalysts at a discharging current density of 10 mA cm −2 .
Source publication
Platinum is commonly chosen as electrocatalyst used for oxygen reduction reaction (ORR). In this study, we report an active catalyst composed of MnO2 nanofilms grown directly on nitrogen-doped hollow graphene spheres, which exhibits high activity toward ORR with positive onset potential (0.94 V vs RHE), large current density (5.2 mA cm-2) and perfe...
Contexts in source publication
Context 1
... open-circuit voltage of MnO 2 / N-HGS was 1.48 V with a peak power density of 82 mW cm −2 , which is comparable to that of Pt/C catalysts (1.49 V and 94 mW cm −2 ) in the Zn−air batteries (Figure 5a). The galvanostatic discharge curves (Figure 5b) indicated that the discharge potentials plateaux decreased when the current densities increased. ...
Context 2
... and 94 mW cm −2 ) in the Zn−air batteries (Figure 5a). The galvanostatic discharge curves (Figure 5b) indicated that the discharge potentials plateaux decreased when the current densities increased. The battery with the MnO 2 /N-HGS catalyst showed voltage plateaux of ≈1.31, ≈1.26, and ≈1.14 V at the discharge current densities of 5, 10, and 25 mA cm −2 , respectively. ...
Context 3
... values are higher than other previous results. 29−31 In the galvanostatic discharge curves (Figure 5c), the voltage of MnO 2 /N-HGS in long-term discharge after 24 h did not drop, highlighting the excellent stability of the MnO 2 / N-HGS catalyst toward ORR. The specific capacity of the Zn− air battery assembled with a MnO 2 /N-HGS air cathode was 744 mA h g −1 (only considering the mass of Zn consumed) at 10 mA cm −2 , comparable with 757 mA h g −1 of Pt/C as air cathode. ...
Citations
... This process involves modifying both the outer shell and the internal architecture of the spheres. As a result, a combination of three different methods (hard, soft, and selftemplating) is utilized alongside a range of preparation techniques (such as selective etching, nanocasting, chemical vapor deposition, and spray pyrolysis) to achieve the desired outcomes [133][134][135][136][137][138][139][140][141]. ...
The global issue for proton exchange membrane fuel cell market development is a reduction in the device cost through an increase in efficiency of the oxygen reduction reaction occurring at the cathode and an extension of the service life of the electrochemical device. Losses in the fuel cell performance are due to various degradation mechanisms in the catalytic layers taking place under conditions of high electric potential, temperature, and humidity. This review is devoted to recent advances in the field of increasing the efficiency and durability of electrocatalysts and other electrode materials by introducing structured carbon components into their composition. The main synthesis methods, physicochemical and electrochemical properties of materials, and performance of devices on their basis are presented. The main correlations between the composition and properties of structured carbon electrode materials, which can provide successful solutions to the highlighted issues, are revealed.
... The spiral hierarchical porous structure consists of disordered carbon with a uniform framework. These results further prove the developed porous structure, which is consistent with the TEM and SEM results and expected to facilitate the diffusion of reactants in the electrochemical process [44]. ...
... The spiral hierarchical porous structure consists of disordered carbon with a uniform framework. These results further prove the developed porous structure, which is consistent with the TEM and SEM results and expected to facilitate the diffusion of reactants in the electrochemical process [44]. To gain insight into the ORR activity of the as-prepared Fe-Nx-GNT, we first carried out cyclic voltammetry (CV) measurements to screen the electrocatalytic activity of activities of the Fe-Nx-GNT-2-1000 and the referenced Pt/C catalysts in Ar and O2-saturated 0.1 M KOH solution using cyclic voltammetry at a scan rate of 10 mV s −1 . ...
A FeNx-C-based catalyst is considered one of the most promising candidates for the highest oxygen reduction reaction (ORR) activities among nonprecious metal-based electrocatalysts. In this work, a unique catalyst of nitrogen-doped twisted macroscopic graphene tubes decorated with Fe-Nx and bamboo-like carbon nanotubes (CNT) was prepared by using twisted iron wire as a template and cyanamide as a carbon source. The microstructure and physicochemical natures of the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopic (XPS), X-ray diffraction (XRD), and nitrogen adsorption/desorption measurements. Torsion can promote the dislocation of the iron wire lattice, and activate the surface Fe atoms, thus leading to the growth of bamboo-like carbon nanotubes and forming iron nitride. The product has a graphene-like macroscopic tube structure and exhibits excellent ORR activity. Such excellent ORR performance may be ascribed to the synergistic effect, including high ORR catalytic sites caused by the dislocation of the iron wire lattice, nitrogen heteroatoms doping, favorable reactant transport channels provided by macroscopic tube structure, and fast electron transfer rate induced by 3D continuous networks.
... As shown in Fig. 8c, after injecting 1 M methanol, the current of the Pt/C electrode decreased sharply, and the current of the MnO 2 and CNTs electrodes also slowly decreased, but the current of MnO 2 /CNTs, MnO 2 /CNTs -400 and MnO X /CNTs -400 decreased slightly. It indicates that the compositing CNTs to MnO 2 is beneficial to improve the methanol tolerance, higher than that of commercial Pt/C catalyst [56]. Meanwhile, we tested the long-term stability of catalyst by the current-time (i-t) chronoamperometry. ...
Manganese oxides have been proved to be a promising low-cost electrocatalyst for oxygen reduction reaction (ORR) and a critical step in systems of zinc-air batteries, however, which is limited by the poor electrical conductivity. In this paper, we introduce carbon nanotubes (CNTs) as conductive supports to further prepare manganese oxide/CNTs composites with bifunctional electrocatalytic activity by the incorporation of redox and calcination two-step approach. Meanwhile, the effects of mass ratio, calcination temperature and oxidation degree on the oxygen reduction reaction (ORR) activity of the composites were studied. The electrocatalytic results showed that the MnO2/CNTs exhibited better electrocatalytic activity than that of manganese dioxide (MnO2) and CNTs when the mass ratio of CNTs to MnO2 was 60%. After calcination at 400 °C and reduction treatment of sulfur (S) to adjust the surface oxygen vacancy concentration and Mn³⁺ content, the ORR and oxygen evolution reaction (OER) bifunctional catalytic activity of the obtained MnOX/CNTs-400 was significantly enhanced. The ORR half-wave potential (E1/2) and bifunctional potential difference (ΔEOER-ORR) between the ORR half-wave potential and OER potential at 10 mA cm⁻² were 0.77 V and 0.92 V, respectively, due to the introducing of highly conductive CNTs, increase of Mn³⁺ content and oxygen vacancy concentration. Furthermore, the composite also exhibits higher methanol tolerance and long-term stability than the commercial Pt/C catalyst, which provided a class of highly efficient ORR/OER bifunctional electrocatalysts with great energy potential.
... The Zn half-cell and ORR/OER half-cells were separated by a Nafion 117 membrane. The discharge polarization curve demonstrated a peak power density of 90 mW/cm 2 at a current density of 150 mA/cm 2 ( Figure S9), which is in line with the literature with Ptbased catalysts (Yu et al., 2016) (Yang et al., 2017). The charge polarization curves show that the b-isomer outperforms the corresponding a-isomer and the charging reaction at all current densities occurs at a lower operating potential in the b-isomer than the a-isomer, ( Figure 3A). ...
We have investigated the role of ligand-isomerism in modulating the mechanisms and kinetics associated with charge/discharge-chemistry of an aqueous metal-air battery. The dominant electron-withdrawing inductive effect (-I effect) and the diminished electron-withdrawing resonance effect (-R effect) in the 〈-NO2 isomer noticeably diminishes the rate of oxygen reduction (ORR) and oxygen evolution reactions (OER) on the catalytic Co-centre. In their β-counterpart, the cumulative –I and –R effects noticeably enhance the OER and ORR kinetics on the same catalytic Co-centre. Therefore, the regioisomerism of the -NO2 functionality amplifies the kinetics of ORR/OER without influencing their mechanistic pathways. When isomeric electrocatalysts are integrated to aid the charge-chemistry of a Zn-air battery, the overpotential could be decreased by ∼250 mV with β-NO2 isomer leading to a round-trip efficiency as high as 60%. This work contributes to the design of novel molecular platforms to target the overall round-trip efficiency of energy storage and conversion devices.
... Currently, the techniques to synthesize MnO x nanomaterials generally involve liquid-phase route. [8][9][10][11][12][13][14][15][16][17] The construction of microstructures in three-dimensional space can occur via the use of templates or altering the agent in solution that controls the structure. Meanwhile, the materials prepared by liquid phase method generally have advantages in crystallinity and homogeneity. ...
Constructing manganese oxide nanoparticles with different crystal structures and morphologies is crucial for the development of improved supercapacitors. Here, zero‐dimensional (0D) α‐MnO2 and δ‐MnO2 nanoparticles were first synthesized by an ultra‐simple solvent‐free synthetic strategy. The α‐MnO2 nanoparticles exhibited better performance for supercapacitors than δ‐MnO2 nanoparticles due to a higher specific surface area and accelerated electrical charge transfer. Two‐dimensional (2D) α‐MnO2 nanosheets and three‐dimensional (3D) flower‐like α‐MnO2 microspheres were also fabricated by the inclusion of surfactants to investigate the effects of morphology on electrochemical storage capacity with the assistance of different surfactants. Notably, 3D α‐MnO2 microspheres exhibited enhanced electrochemical properties than 0D α‐MnO2 nanoparticles and 2D α‐MnO2 nanosheets for supercapacitors, and generated a favorable specific capacitance of 212.8 F g⁻¹ at 1 A g⁻¹, primarily originating from high porosity, which allows the full infiltration of electrolytes and the rapid shuttling of ions. This work thus describes a simple strategy for the synthesis of 2D nanosheets and 3D self‐assembled nanostructures of MnO2 for application in supercapacitor development.
... [24][25][26][27][28][29][30] Among non-precious metal-based alternatives, manganese oxides have shown promise as the oxygen catalysts for Zn-air batteries due to their good activity for ORR. [31][32][33][34] Further, some manganese oxides have also demonstrated good catalytic activity toward the OER, indicating their capability as bifunctional oxygen catalysts. [35,36] However, the activity of manganese oxides is usually inferior to that of precious metals. ...
Bifunctional oxygen catalyst is an important component in the cathode for rechargeable zinc‐air batteries. MnO2 catalysts have aroused intense interests owing to their promising activity for oxygen reduction reaction (ORR), which, however, is still not comparable to precious metal catalysts. To improve the ORR catalysis and meet the requirement for a bifunctional oxygen catalyst, MnO2 nanosheets are modified with Co, Ni or Fe via a facile solution‐based method. Among the modified samples, Co−MnO2 presents improved catalysis for both ORR and oxygen evolution reaction (OER). The modification introduces additional active sites for OER and induced more oxygen defects to further facilitate the ORR. Zn‐air batteries with the Co−MnO2 air cathode showed a higher peak power density of 167 mW cm−2, a lower potential gap of 0.75 V and a higher round‐trip efficiency of 63 % (5 mA cm−2) compared to MnO2 without modification. Good cycling stability of the battery is also achieved. The proper amount of cobalt species in the MnO2 is vital for achieving a balance between high performance and durable cycling.
... In addition, various strategies including preparing MnO 2 nanofilm on N-doped hollow graphene [120], integrating Mn 3 O 4 with rGO-IL [125], integrating CoMn 2 O 4 with NrGO [124], integrating MnCoFeO 4 with N-rGO [126], functionalizing graphene oxide with 1-hexyl-3methylimidazolium chloride molecules [121], integrating Co 3 O 4 with N doped graphene [122], integrating Co 3 O 4 nano-rods with reduced graphene oxide [118], preparing predominant metallic Co with small fraction of its oxides anchored on N-doped reduced graphene oxide [123], integrating amorphous bimetallic oxide with N-doped reduced graphene oxide [117], and integrating Fe-doped NiOOH with graphene-encapsulated FeNi 3 [119] enhanced the ORR/OER activity and ZAB performance. ...
... depicts the ORR/OER activity and zinc-air battery performance of various kinds of reported graphene with metal oxides based air catalysts[37,[117][118][119][120][121][122][123][124][125][126]. Preparing MnO 2 nanofilm on N-doped hollow graphene can enhance the ORR activity and ZAB performance. ...
... Yu et. al.[120] have observed that MnO 2 -NG exhibits high ORR activity with high ZAB performance. It was prepared by template method and mild oxidation process through the following steps: At first, SiO 2 @rGO was obtained by drying the silica/graphene oxide suspension for overnight at 80 C followed by heating at 850 C for 2 h under N 2 atmosphere; Then, hollow graphene spheres was obtained by removal of SiO 2 templates by etching with 10 wt % of HF for 12 h at room temperature; Later, NG was prepared by hydrothermal treatment of the above hollow graphene with NH 4 OH at 180 C for 8 h followed by annealing at 800 C for 2 h under N 2 atmosphere; Finally, MnO 2 -NG was obtained by treating NG with 0.012 mol L 1 of KMnO 4 at 60 C for 2 h followed by annealing at 800 C for 2 h under N 2 atmosphere. ...
The development of cheap and efficient oxygen reduction and evolution reaction catalysts are important, which not only push the electrochemical energy systems including water electrolyzers, metal-air batteries, and fuel cells nearer to their theoretical limits but also become the substitute for the expensive noble metal catalysts (Pt/C, IrO2 or RuO2 and Pt-Ru/C). In this review, the recently reported potential graphene-based air catalysts such as graphene with non-metals, non-noble metals, metal oxides, nitrides, sulfides, carbides, and other carbon composites are identified in-light-of-their high oxygen reduction reaction/oxygen evolution reaction activity and zinc-air battery performance for the development of high energy density metal-air batteries. Further, the recent progress on the zinc-air batteries including the strategies used to improve the high cycling-performance (stable even up-to 394 cycles), capacity (even up-to 873 mAh g⁻¹), power density (even up-to 350 mW cm⁻²), and energy density (even up-to 904 W h kg⁻¹) are reviewed. The scientific and engineering knowledge acquired on zinc-air batteries provide conceivable development for practical application in near future.
... The Co/N-CNS-2 with optimized ORR catalytic performance comes from unique 3D honeycombed porous structures with uniform distributions of highly active Co/N x active sites among carbon skeletons [51,52]. More importantly, the ORR catalytic properties of the Co/N-CNS-2 exceed most heteroatom-doped carbon catalysts reported in the literature (table 1) [6,8,11,29,30,[53][54][55][56][57][58][59]. ...
The broad application of metal-air battery and fuel cell have been greatly limited due to their slow kinetics of oxygen electrodes involving the oxygen reduction reaction (ORR), and therefore the development of high-efficient, low-cost and high-reserve ORR electrocatalysts is of great significance. Herein, a hypersaline-protected pyrolysis strategy is presented for preparing 3D honeycombed cobalt, nitrogen co-doped carbon nanosheets (Co/N-CNS) by using eco-friendly biomass as a carbon and nitrogen source. During the hypersaline-protected pyrolysis, the pyridinic nitrogen-rich biomass facilitates the formation of highly active Co/N active sites among the resultant Co/N-CNS, while the templating-washing-drying cyclic utilization of salts creates honeycombed pore structures among the Co/N-CNS. Due to the structural features of honeycombed pores and uniform distributed active sites, the Co/N-CNS catalyst offers excellent ORR activity, high durability and methanol-tolerant performance in an alkaline electrolyte. As a demonstration, a primary Zn-air battery using the Co/N-CNS cathode delivers a high power density and excellent operating stability beyond that of commercial Pt/C cathode.
... It is necessary to increase ORR performance of Mn 3 O 4 by merging with highly porous materials having large surface area and conductivity. Unfortunately, conventional methods to produce porous materials used hard templates and these templates are removed by hazardous acid leaching [31]. Metaleorganic frameworks (MOFs, such as ZIF-8) derived porous carbon materials having highly mesoporous structures and suitable surface area are well-known because of their potential for applications [4,12,13,32e34]. ...
Engineering the morphology of integral building blocks is a key step in broadening their catalytic activities. In this work, an interesting structure is reported by oriented and directed growth of manganese oxide (Mn3O4) quasi-nanocubes on nitrogen doped mesoporous carbon polyhedrons resulting from zeolite imidazole framework (ZIF-8). The prepared Mn3O4/NCP (Mn3O4 quasi-nanocubes on the surface of N-doped carbon polyhedrons) hybrid catalyst showed activity and durability comparable to Pt/C and higher than nitrogen-doped carbon polyhedrons (NCP) and pure Mn3O4. Further studies indicate that oxygen reduction reaction (ORR) is carried out via a four electron transfer mechanism with very low production of hydrogen peroxide (3%). In this perspective, Mn3O4/NCP is an auspicious nominee as a cathodic catalyst because of inexpensive Mn and good durability. Our synthetic strategy may open a new avenue for material synthesis.
... Due to the bimetallic active sites, large surface area, high nitrogen doping level, uniform Fe-N x distribution, and conductive carbon frameworks, the Cu@Fe-N-C exhibited excellent ORR performance. Furthermore, the composite materials always not only combine the advantages of each material, but also bring synergistic effects to enhance the ORR process, including the metal oxide/metal oxide [199,211,217,258,259,268,269], metal oxides/carbon materials [42,217,225,261,[269][270][271][272][273] and carbon materials doped with atoms [52,220,222,242,[274][275][276]. For example, Shao et al. [211] found the Co 3 O 4 -CeO 2 /ketjenblack (KB) showed much better electrocatalytic performance than both Co 3 O 4 /KB and CeO 2 /KB due to the synergistic effects between Co 3 O 4 and CeO 2 . ...
Aqueous metal-air batteries have gained much research interest as an emerging energy storage technology in consumer electronics, electric vehicles, and stationary power plant recently, primarily due to their high energy density derived from discarding the bulkier cathode chamber. In addition, abundant raw materials, low cost, high safety, and environmental friendliness are intrinsic advantages of metal-air batteries as well. Motivated by the desirable characteristics, the significant progress has been made in promoting the promising electrochemical performance and improving the long-term stability in aqueous metal-air batteries in recent years. This review article starts with a general description of the features and working principles of aqueous metal-air battery systems. Then, the air cathode structures are introduced and compared, as well as the electrochemical catalysts applied in the air cathode are comprehensively summarized, including noble metals, alloys, metal oxides, hydroxides or sulfides, carbon materials, as well as the composite materials such as metal (oxides)/metal oxides and (metal) oxides/carbon materials. In addition, the chemistries and major issues of metal anodes, e.g. aluminum, zinc and magnesium, are reviewed and respective strategies to alleviate these issues are offered as well. Afterwards, detailed discussions have been provided on the recent progress towards the electrolytes and separators, both of which are crucial components in the battery configuration. From the system point of view, innovative single-cell and stack system designs are also presented. Finally, the challenges and perspectives for the future development of aqueous metal-air batteries are highlighted.
