Composition-optimized manganese phosphide nanoparticles anchored on porous carbon network for efficiently electrocatalytic hydrogen evolution

Electrocatalytic water splitting is an efficient method for producing high purity hydrogen and has the advantage of emitting zero waste. Manganese phosphides are considered to be promising electrocatalysts for the hydrogen evolution reaction (HER) with their electrocatalytic properties being composition-dependent. In this work, we achieved the targeted synthesis of manganese-rich Mn2P, phosphorus-rich MnP, and their heterostructure Mn2P-MnP nanoparticles dispersed uniformly on a P, N-doped carbon network (Mn2P-MnP/PNC) through a facile strategy involving the use of phosphate resin derived with potassium hydroxide. Systematic studies were conducted on formation mechanism of Mn2P-MnP/PNC. Density functional theory (DFT) calculations indicate that Mn2P-MnP has an optimized electronic structure and Gibbs free energy of H adsorption, with that of Mn2P-MnP (0.057 eV) being closest to zero compared to Mn2P (-0.306 eV) and MnP (0.325 eV). The Mn2P-MnP/PNC only requires small overpotentials of 63 and 98 mV to achieve 10 mA cm−2 for HER in H2SO4 and KOH solution, respectively. Furthermore, Mn2P-MnP/PNC exhibits ultrahigh stability for HER in both acid and alkaline solutions, retaining a current rate of 98.18% and 97.57% after 96 and 120 h chronoamperometry tests, respectively.