Surface Modification towards Integral Bulk Catalysts of Transition Metal Borides for Hydrogen Evolution Reaction

Transition metal borides (TMBs) are promising catalysts for hydrogen evolution reaction (HER). While the commercially available TMBs indicate poor HER performance due to powder electrode and low activity sites density, optimizing commercial TMBs for better HER performance is urgent. To break through the challenge, a new strategy is proposed to compose integral bulk electrodes with needle surfaces in TMBs. The integral bulk electrodes in TiB2, ZrB2, and HfB2 are formed under high pressure and high temperature (HPHT), and the nanoneedle morphology is constructed by chemical etching. In the three materials, the smallest overpotential is 346 mV at 10 mA cm−2 in the HCl etched bulk TiB2 electrode, which is about 61.9% higher than commercial TiB2 powder. Better performance arises from better conductivity of the integral bulk electrode, and the nano morphology exposes the edge sides of the structure which have high activity site density. This work is significant for developing new kinds of bulk TMBs catalysts.