writer：Liu Dandan Li Liangjun Xu Huanfei Dai Pengcheng Wang Ying Gu Xin Yan Liting Zhao Guoming Zhao Xuebo
keywords：MOF ORR
source：期刊
specific source：CHEMISTRY-AN ASIAN JOURNAL ，2018，13，10，1318-1326
Issue time：2018年
N‐doped carbon materials represent promising metal‐free electrocatalysts for the oxygen reduction reaction (ORR), the cathode reaction in fuel cells, metal–air batteries, and so on. A challenge for optimizing the ORR catalytic activities of these electrocatalysts is to tune their local structures and chemical compositions in a rational and controlled way that can achieve the synergistic function of each factor. Herein, we report a tandem synthetic strategy that integrates multiple contributing factors into an N‐doped carbon. With an N‐containing MOF (ZIF‐8) as the precursor, carbonization at higher temperatures leads to a higher degree of graphitization. Subsequent NH3 etching of this highly graphitic carbon enabled the introduction of a higher content of pyridine‐N sites and higher porosity. By optimizing these three factors, the resultant carbon materials displayed ORR activity that was far superior to that of carbon derived from a one‐step pyrolysis. The onset potential of 0.955?V versus a reversible hydrogen electrode (RHE) and the half‐wave potential of 0.835?V versus RHE are among the top ranks of metal‐free ORR catalysts and are comparable to commercial Pt/C (20?wt?%) catalysts. Kinetic studies revealed lower H2O2 yields, higher electron‐transfer numbers, and lower Tafel slopes for these carbon materials compared with that derived from a one‐step carbonization. These findings verify the effectiveness of this tandem synthetic strategy to enhance the ORR activity of N‐doped carbon materials.