Boosting alkaline hydrogen evolution of Co/Co(OH)₂ nanosheet arrays with molybdate modification

The development of efficient and low-cost electrocatalysts for alkaline hydrogen evolution reaction (HER) is crucial for the sustainable hydrogen generation. However, the sluggish water dissociation kinetics limits the HER efficiency. Herein, molybdate ion (MoO₄^2-) modified Co/Co(OH)₂ nanosheet arrays (MCC NSAs) were constructed via a facile two-step method involving electrodeposition and subsequent impregnation. The modification of MoO₄^2- species induce the electron transfer from MoO₄^2- to Co/Co(OH)₂, optimizing the adsorption behavior of reaction intermediates and accelerating the water dissociation process. As a result, MCC NSAs exhibit excellent alkaline HER performance. The overpotential is only 41 mV to achieve a current density of 10 mA cm^-2, outperforming the pristine Co/Co(OH)₂ NSAs, and even rivaling the Pt/C benchmark. The electrochemical studies, in-situ Raman, and density functional theory (DFT) calculations manifest that the remarkable activity originates from the increased electrochemically active surface area, accelerated water dissociation process, strengthened water adsorption, and optimized hydrogen adsorption free energy. Moreover, MCC NSAs exhibit outstanding durability for over 250 h at 200 mA cm^-2.