The rational design and construction of hierarchically porous nanostructure for oxygen reduction reaction (ORR) electrocatalysts is crucial to facilitate the exposure of accessible active sites and promote the mass/electron transfer under the gas-solid-liquid triple-phase condition. Herein, an ingenious method through the pyrolysis of creative polyvinylimidazole coordination with Zn/Fe salt precursors is developed to fabricate hierarchically porous Fe-N-doped carbon framework as efficient ORR electrocatalyst. The volatilization of Zn species combined with the nanoscale Kirkendall effect of Fe dopants during the pyrolysis build the hierarchical micro-, meso-, and macroporous nanostructure with a high specific surface area (1,586 m2·g−1), which provide sufficient exposed active sites and multiscale mass/charge transport channels. The optimized electrocatalyst exhibits superior ORR activity and robust stability in both alkaline and acidic electrolytes. The Zn-air battery fabricated by such attractive electrocatalyst as air cathode displays a higher peak power density than that of Pt/C-based Zn-air battery, suggesting the great potential of this electrocatalyst for Zn-air batteries.
To commercialize fuel cells and metal-air batteries, cost-effective, highly active catalysts for the oxygen reduction reaction (ORR) must be developed. Herein, we describe the development of low-cost, heteroatom (N, P, Fe) ternary-doped, porous carbons (HDPC). These materials are prepared by one-step pyrolysis of natural tea leaves treated with an iron salt, without any chemical and physical activation. The natural structure of the tea leaves provide a 3D hierarchical porous structure after carbonization. Moreover, heteroatom containing organic compounds in tea leaves act as precursors to functionalize the resultant carbon frameworks. In addition, we found that the polyphenols present in tea leaves act as ligands, reacting with Fe ions to form coordination compounds; these complexes acted as the precursors for Fe and N active sites. After pyrolysis, the as-prepared HDPC electrocatalysts, especially HDPC-800 (pyrolyzed at 800 °C), had more positive onsets, half-wave potentials, and higher catalytic activities for the ORR, which proceeds via a direct four-electron reaction pathway in alkaline media, similar to commercial Pt/C catalysts. Furthermore, HDPC-X also showed enhanced durability and better tolerance to methanol crossover and CO poisoning effects in comparison to commercial Pt/C, making them promising alternatives for state-of-the-art ORR electrocatalysts for electrochemical energy conversion. The method used here provides valuable guidelines for the design of high-performance ORR electrocatalysts from natural sources at the industrial scale. 相似文献
Oxygen reduction reaction catalysts based on precious metals such as platinum or its alloys are routinely used in fuel cells because of their high activity. Carbon-supported materials containing metals such as iron or cobalt as well as nitrogen impurities have been proposed to increase scalability and reduce costs, but these alternatives usually suffer from low activity and/or gradual deactivation during use. Here, we show that few-walled carbon nanotubes, following outer wall exfoliation via oxidation and high-temperature reaction with ammonia, can act as an oxygen reduction reaction electrocatalyst in both acidic and alkaline solutions. Under a unique oxidation condition, the outer walls of the few-walled carbon nanotubes are partially unzipped, creating nanoscale sheets of graphene attached to the inner tubes. The graphene sheets contain extremely small amounts of irons originated from nanotube growth seeds, and nitrogen impurities, which facilitate the formation of catalytic sites and boost the activity of the catalyst, as revealed by atomic-scale microscopy and electron energy loss spectroscopy. Whereas the graphene sheets formed from the unzipped part of the outer wall of the nanotubes are responsible for the catalytic activity, the inner walls remain intact and retain their electrical conductivity, which facilitates charge transport during electrocatalysis. 相似文献
Heteroatom-doped porous carbon has attracted many researchers'interests owing to their hierarchical porous and more active sites for nitrogen reduction reaction... 相似文献
The requirement for a sustainable and renewable energy has inspired substantial interests in designing and developing earth-abundant and high-effectiveness electrocatalysts/electrodes for fuel cells and metal-air batteries, in which oxygen reduction reaction(ORR) plays a crucial role. Perovskite oxides have acquired rapid attention as ORR electrocatalysts to replace noble-metal-based catalysts owing to their intrinsic electrocatalytic activity, compositional and structural flexibility. Herein, we report a new Sc and P co-doped perovskite oxide(La_(0.8)Sr_(0.2)Mn_(0.95)Sc_(0.025)P_(0.025)O_(3-δ), LSMSP) as an active and robust electrocatalyst for the ORR in an alkaline solution. LSMSP electrocatalyst shows superior ORR activity and stability than those of pristine La_(0.8)Sr_(0.2)MnO_(3-δ)(LSM), Sc-doped LSM and P-doped LSM due to the optimized average valence of Mn ions, the large surface area, the smaller particle size and the synergetic effect introduced by the co-doping. Moreover, compared to the benchmark Pt/C electrocatalyst, LSMSP electrocatalyst displays comparable ORR activity and superior durability. These above results suggest that the co-doping strategy of Sc and P into perovskites is a useful method to design high-performance electrocatalysts for the ORR, which can be used in other electrocatalysis-based applications. 相似文献
N-doped porous carbon materials have been prepared by a simple one-step pyrolysis of ethylenediaminetetraacetic acid (EDTA) and melamine in the presence of KOH and Co(NO3)2·6H2O. The combination of the high specific area (1485 m2·g?1), high nitrogen content (10.8%) and suitable graphitic degree results in catalysts exhibiting high activity (with onset and half-wave potentials of 0.88 and 0.79 V vs the reversible hydrogen electrode (RHE), respectively) and four-electron selectivity for the oxygen reduction reaction (ORR) in alkaline medium—comparable to a commercial Pt/C catalyst, but far exceeding Pt/C in stability and durability. Owing to their superb ORR performance, low cost and facile preparation, the catalysts have great potential applications in fuel cells, metal-air batteries, and ORR-related electrochemical industries. 相似文献
The transition metal dichalcogenides, such as TiS2, have been reported to perform well as cathodes in ambient temperature lithium batteries. It has been found that the layered, transition metal phosphorus trisulfides also exhibit electrochemical activity. Nickel phosphorus trisulfide will react with more than four lithium resulting in a cell with a theoretical energy density double that of titanium disulfide. 相似文献
Nano Research - Rechargeable lithium-iodine (Li-I2) battery is a promising energy storage system because of the high energy and power density. However, the shuttle effects of iodine species and the... 相似文献
A composite air electrode consisting of Ketjenblack carbon (KB) supported amorphous manganese oxide (MnOx) nanowires, synthesized via a polyol method, is highly efficient for the oxygen reduction reaction (ORR) in a Zn-air battery. The low-cost and highly conductive KB in this composite electrode overcomes the limitations due to low electrical conductivity of MnOx while acting as a supporting matrix for the catalyst. The large surface area of the amorphous MnOx nanowires, together with other microscopic features (e.g., high density of surface defects), potentially offers more active sites for oxygen adsorption, thus significantly enhancing ORR activity. In particular, a Zn-air battery based on this composite air electrode exhibits a peak power density of ~190 mW/cm2, which is far superior to those based on a commercial air cathode with Mn3O4 catalysts. 相似文献