Reconstruction of a surficial P-rich layer on Ni-P electrocatalysts for efficient hydrogen evolution applicable in acidic and alkaline media

Ni-P is a promising catalytic material for the hydrogen evolution reaction (HER) due to its high catalytic activity, highly competitive cost, and practical usefulness. To achieve the best catalytic performance with the Ni-P-based material, it is necessary to control the P ratio in Ni-P because the catalytic kinetics of Ni-P depend on the number of reaction sites of the positively and negatively charged Ni and negatively charged P to adsorb the hydride/hydroxide and proton in acidic and alkaline media. Here, we introduce a facile surface-treatment based on dealloying to control the surficial P ratio with multiple CV cycles. As a result, the 20 and 10 times cycled Ni-P/CFPs show improved catalytic activities of 30.8% and 23.5% along with higher stabilities of 99.8 and 97.9% retention in acid and alkaline media, respectively. In particular, the different kinetics according to P ratio in both acid and alkaline media can be elucidated by DFT calculations of the free energy changes related to each RDS.