A study of the mechanism of the hydrogen evolution reaction catalysed by molybdenum phosphide in different media

The electrochemical decomposition of water is an effective method of green hydrogen production due to the purity and renewability of the process. The production of hydrogen occurs through the hydrogen evolution reaction (HER), and the process may be facilitated by using proper catalysts. Transition metal phosphides (TMPs), especially MoP, can potentially replace expensive Pt-based catalysts. However, most studies deal with experimental research without DFT simulations, and the process's mechanism is not described in detail. Therefore, this study aims to investigate the catalytic performance and reaction mechanism of an MoP catalyst for HER across all pH ranges and combine electrochemical analysis with simulations to gain deeper mechanistic insights. MoP surfaces with (101), (110) and (100) facets are prepared and investigated with experimentally synthesised MoP samples studied in acidic, alkaline, and neutral media. MoP catalyst exhibits superior HER activity in an alkaline media with charge transfer resistance ( Rct ) of 7.12 Ω. DFT results also showed that H 2 O adsorption is preferred on MoP(101) and MoP(110) with adsorption energy ( ΔE ad ) of −0.93 eV and −1.21 eV, respectively. Based on experimental and DFT results, a proposed HER mechanism considers various MoP facets and different media. • MoP catalyst showed excellent HER activity in alkaline media with R ct of 7.12 Ω Ω. • Calculated ΔG H∗ for MoP(101), (110) and (100) was −0.66 eV, −0.51 eV and −0.15 eV. • H 2 O adsorption is preferred on MoP(101) and (110) with E ad −0.93 eV and −1.21 eV. • HER mechanism was proposed for MoP(101), (110) and (100) surfaces.