Activating MoO4 tetrahedrons to MoOx species in MoNi alloy for boosting performance in alkaline hydrogen evolution reaction

Abstract

MoNi alloys as excellent alkaline hydrogen evolution reaction (HER) electrocatalysts benefit from activated Mo-based polymerides for optimizing hydrogen desorption of Ni site. Mo-based polymerides are transformed from adsorbed MoO42−, which is formed by dissolved Mo. However, the dissolution behavior of Mo is uncontrollable and adsorbed MoO42− is limited, resulting in reduced activity of the MoNi alloys. Herein, we reported a unit cell activation strategy to prepare activated MoOx species in MoNi (MoOx/MoNi) alloy for boosting performance in alkaline HER. Characterization by Raman spectroscopy shows that activated MoOx species in MoNi alloy are mainly derived from MoO4 tetrahedrons of the β-NiMoO4 under HER, which have strong correlation with the HER performance of the catalyst. The obtained MoOx/MoNi performs a brilliant HER activity with a low overpotential and Tafel slope of 35 mV@10 mA cm−2 and 58 mV dec−1, respectively, even surpassing commercial Pt/C. As revealed by a series of characterization techniques and theoretical methods, the brilliant HER activity can be ascribed to both the capacity of MoOx on adjusting the hydrogen desorption of Ni site and the intrinsic property of the MoNi alloy. Significantly, activating MoO4 tetrahedrons to MoOx species is an efficient way to replace the self-dissolution and restructure of Mo in MoNi alloy, which could effectively minimize the adverse effect of dissolved Mo on the catalytic activity of MoNi alloy. This work demonstrates the activation process of MoO4 tetrahedrons to MoOx species, providing a new insight into designing and fabricating high-performance HER catalysts by unit cell activation instead of self-dissolution and restructure.