The Hydrogen Evolution Reaction (HER) is critical for attaining a “hydrogen economy”. Currently, industry relies on expensive platinum group metal (PGM) catalysts, providing incentive for the development of earth abundant catalysts. For this purpose, several binary materials consisting of transition metal and light p-block elements have emerged as excellent alternatives to PGMs. From this class, nickel phosphide (Ni<sub>2</sub>P) nanocrystals have shown to exhibit excellent HER capabilities. However, under operational conditions, various degradation mechanisms exist, which prevent it from becoming commercially viable. By using comparative Density Functional Theory (DFT) calculations and experimental testing, we show how Ni<sub>2</sub>P can be readily functionalized using a range of diazonium salts. The functionalized materials exhibit improved electrocatalytic activity and stability for the HER compared to the unfunctionalized material. Specifically, we show how the hydrogen binding free energy and electronic structure can be readily modulated as a function of the surface functional group coverage and Hammett parameter.

Covalent functionalization of nickel phosphide nanocrystals with aryl-diazonium salts

ACS Spring 2022

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