Long Xinghui, Yu Pengfei, Zhang Nian, Li Chun, Feng Xuefei, Ren Guoxi, Zheng Shun, Fu Jiamin, Cheng Fangyi, Liu Xiaosong
State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.
CAS Center for Excellence in Superconducting Electronics (CENSE), Chinese Academy of Sciences, Shanghai 200050, China.
Nanomaterials (Basel). 2019 Apr 9;9(4):577. doi: 10.3390/nano9040577.
Nanocrystalline multivalent metal spinels are considered as attractive non-precious oxygen electrocatalysts. Identifying their active sites and understanding their reaction mechanisms are essential to explore novel transition metal (TM) oxides catalysts and further promote their catalytic efficiency. Here we report a systematic investigation, by means of soft X-ray absorption spectroscopy (sXAS), on cubic and tetragonal CoMnO₄ (x = 1, 1.5, 2) spinel oxides as a family of highly active catalysts for the oxygen reduction reaction (ORR). We demonstrate that the ORR activity for oxide catalysts primarily correlates to the partial covalency of between O 2p orbital with Mn 3d t-down/e-up, Mn 3d e-up and Co 3d e-up orbitals in octahedron, which is directly revealed by the O K-edge sXAS. Our findings propose the critical influences of the partial covalency between oxygen 2p band and specific metal 3d band on the competition between intermediates displacement of the ORR, and thus highlight the importance of electronic structure in controlling oxide catalytic activity.
纳米晶多价金属尖晶石被认为是有吸引力的非贵金属氧电催化剂。识别其活性位点并了解其反应机制对于探索新型过渡金属（TM）氧化物催化剂并进一步提高其催化效率至关重要。在此，我们通过软X射线吸收光谱（sXAS）对立方和四方CoMnO₄（x = 1, 1.5, 2）尖晶石氧化物作为氧还原反应（ORR）的一类高活性催化剂进行了系统研究。我们证明，氧化物催化剂的ORR活性主要与八面体中O 2p轨道与Mn 3d t-向下/e-向上、Mn 3d e-向上和Co 3d e-向上轨道之间的部分共价性相关，这由O K边sXAS直接揭示。我们的研究结果提出了氧2p带与特定金属3d带之间的部分共价性对ORR中间体位移竞争的关键影响，从而突出了电子结构在控制氧化物催化活性中的重要性。
