Three-dimensional porous structural MoP2 nanoparticles as a novel and superior catalyst for electrochemical hydrogen evolution

Abstract

Abstract Transition metal phosphides (TMPs) are burgeoning as novel electrocatalysts to replace noble metals for electrochemical production of hydrogen. In this work, we propose a novel and cost-effective catalyst, molybdenum diphosphide (MoP2) three-dimensional porous structural nanoparticles with superior activity towards the hydrogen evolution reaction (HER). MoP2 nanoparticles catalyst exhibits an onset overpotential of −38 mV, a Tafel slope of 52 mV dev−1 and an exchange current density of 0.038 mA cm−2. Furthermore, the catalyst only needs low overpotentials of −121 and −193 mV to produce operationally relevant cathodic current densities of −10 and −100 mA cm−2, respectively, and its catalytic activity is maintained for at least 24 h. Comparative study with MoP nanoparticles as electrocatalyst for HER clearly indicates that MoP2 with high phosphor component can potentially improve the electrocatalytic activities. Density functional theory (DFT) calculation shows that the higher electrocatalytic activity of MoP2 over MoP can be attributed to a longer H P bond length, lower hydrogen adsorption energy, lower HER energy barrier and luxuriant surface active sites. This work may expand the TMPs family to poly-phosphides as active and cost-effective hydrogen electrode for the large-scale hydrogen production.