Silver-decorated cobalt-molybdenum oxide nanosheets as a pH-universal electrocatalyst for high-efficiency hydrogen evolution reaction

The high efficiency of hydrogen evolution reaction (HER) catalysts depends on their electronic structure, conductivity, and intrinsic catalytic activity. Transition-metal oxides (TMO) present a great potential to replace platinum-based catalysts, but further improvements in intrinsic catalytic activity are limited to the materials' conductivity. Herein, theoretical calculations disclosed that the adjusted density of states around the Fermi level caused by Ag introduction increased the conductivity of Co2Mo3O8-Ag, optimizing the water adsorption energy (?E-ad) and Gibbs free energy of hydrogen adsorption (?G(H*)). This can be rationalized through the synergistic effect between electron-rich Co and Mo sites in Co2Mo3O8-Ag. Inspired by this, Ag nanoparticles loaded on Co2Mo3O8 nanosheets (CMO-Ag) as a pH-universal HER catalyst were successfully constructed. As expected, the prepared CMO-Ag catalyst exhibited excellent HER activity with overpotentials of 55.5, 63.2, and 68.2 mV at a current density of 10 mA cm(-2) in alkaline, neutral, and acidic electrolyte, respectively, superior to most reported results from molybdenum/cobalt-based electrocatalyst. Meanwhile, the CMO-Ag also presented exceptional stability with negligible change after 20 h of stability tests and 1000 cycles of CV measurements. This work provides a valuable strategy for optimizing catalytic activity sites and improving conductivity through combining metal nanoparticles and TMO, which can be applied for other TMO-based HER pH-universal catalyst.