Molten salt assisted Co1−xAgxMoO4 with lattice Ag doping and oxygen vacancy for stable water oxidation

Abstract

Spinel type oxides including CoMoO4 are promising catalysts for water electrolysis. However, MoO42− is easy to dissolve during oxygen evolution reaction (OER), resulting in the poor performance. The lattice modulation of CoMoO4 may be an effective strategy for better activity and stability. In our work, molten salt method has been adopted to realize the incorporation of Ag into the lattice surface of CoMoO4 nanorods. The physical characterizations show that Ag is uniformly distributed in the surface lattice of optimized Co1−xAgxMoO4. Lattice Ag doping stabilizes the structure of Co1−xAgxMoO4 by adjusting the electron distribution state to form a high-valence Co. Moreover, the incorporation of low-valence Ag+ causes the Co1−xAgxMoO4 to produce more oxygen vacancies, which reduces the charge transfer resistance by about 15 times compared to CoMoO4. The electrochemical measurements demonstrate that Co1−xAgxMoO4 exhibits a lower OER overpotential (330 mV) at 10 mA cm−2 and the 2.7 longer time than CoMoO4 during chronopotentiometry test. DFT calculation reveals that Ag doping with ion polarization optimizes the electron distribution of Co-O and enhances the covalency of Mo-O to slow down the solubility of Co1−xAgxMoO4. This work shows that lattice doping of metal ions may be a great choice for excellent electrocatalysts for OER.