Hydrate catalysts enabled the self-reconstruction of NiMoO4 for efficient water oxidation

Abstract

Transition metal-based pre-catalysts undergo drastic reconstruction to form active catalysts during the alkaline oxygen evolution reaction. However, little is known about how pre-catalysts affect the activity of the in situ generated active species. Herein, the reconstruction degree is modulated by varying hydrate/anhydrous molybdate pre-catalysts, which will reveal the effects of pre-catalysts in the OER activity. The hydrate molybdate not only presents a faster reconstruction rate but also outstanding OER activity and stability, and exhibits a low overpotential of only 206 mV at 10 mA cm⁻² in an alkaline solution. Experimental investigations reveal that the oxide hydroxides/hydroxyls derived from hydrates exhibit a larger surface area, and a higher concentration of OH⁻ on the surface, which accelerates the OER kinetics rate. Furthermore, the lattice oxygen was triggered and therefore able to react via a faster lattice-oxygen-mediated mechanism (LOM) pathway, which presents lower thermodynamic barriers compared to catalysts derived from anhydrous pre-catalysts. This work may provide new insight into elucidating the OER activity enhancement mechanism.