Engineering the coordination environment enables molybdenum single-atom catalyst for efficient oxygen reduction reaction

With a half filled d-electron shell, molybdenum (Mo) plays an important role as catalysts in the petrochemical industry. However, Mo is generally regarded as not catalytically active for oxygen reduction reaction (ORR) compared with other transition metals such as Fe and Co. Inspired by molybdoenzymes, herein, we successfully endow Mo single-atom catalyst with highly ORR catalytic activity though engineering the coordination environment. This unique Mo single-atom catalyst consists of oxygen and nitrogen dual-component coordinated central Mo atom anchored on porous carbon (Mo-O/N-C), showing prominent ORR catalytic performance compared to the state-of-the-art Pt/C under alkaline condition. The extraordinary performance of Mo-O/N-C electrocatalyst is also demonstrated in Zn-air batteries as an air cathode. Density functional theory (DFT) calculations reveal the oxygen and nitrogen dual-component coordination could tailor the d-band center of Mo, subsequently optimizing its binding capability with reaction intermediates (O*, OH* and OOH*), hence accelerating overall ORR process. This work not only provides an efficient and commercially competitive ORR catalyst, but advancing further development of other electrocatalysts through engineering the coordination environment.