Theoretical insights of electrocatalytic hydrogen evolution on MoP nanocrystal

Abstract

A methodical computational investigation was performed to gain insights into the factors and mechanisms that determine the catalytic activity of molybdenum phosphide (MoP). We analysed the structure and energetics as well as hydrogen adsorption behaviour on the (100) crystallographic plane of MoP. The Gibbs free energy and density of states studies were performed to elucidate the crystal chemistry and bonding mechanism of MoP(100) with the adsorbate. The computed values of ΔGH∗ at different hydrogen coverages are then used to predict the hydrogen evolution reaction (HER) activity on the (100) surface. The obtained values of hydrogen Gibbs free energy of adsorption ΔGH showed HER activity ranging between −0.35 and 0.10 eV. Our study has placed the (100) surface of MoP nanoparticles as highly suited analogues to platinum in the HER. The high intrinsic activity of MoP(100) is a result of a distinct electronic structure induced by the presence of phosphorus a phenomenon known as a ‘ligand effect’. The presence of phosphorus benefits the catalyst by improving intrinsic catalytic activity and enhancing proton adsorption kinetics. The results obtained from this study proved that phosphorizing and surface faceting play a crucial role in enhancing the catalytic performance of transition metals. Key trends that underpin the potential of MoP(100) as a catalyst for improved HER were identified, with a view to implement these findings for the practical design of improved catalysts for hydrogen production based on molybdenum phosphide.