P-doped MOF-derived NiMo bimetallic sulfide used as a high efficiency electrocatalyst for oxygen evolution reaction

Abstract

Metal–organic frameworks (MOF) were used as templates to prepare transition metal sulfides and phosphides in order to expose the active site of the material to a greater extent. Utilizing the synergistic effect of bimetals, Ni²⁺ and Mo⁶⁺ were selected as metal ion centers and trimesic acid was selected as the ligand to prepare NiMo-MOFs by the hydrothermal method. Then, NiMo-P, NiMo-S and NiMo-P/S were prepared using NiMo-MOFs as the precursor, and the preparation conditions of the abovementioned hybrids were optimized through linear sweep voltammetry. The results show that when the molar ratio of NiMo-MOF to NaH₂PO₂ is 1 : 5, and the as-prepared NiMo-P is further doped with S in a proportion of 1 : 1, the overpotential of the final NiMo-P/S hybrid is 313 mV at a current density of 10 mA cm⁻², and its electrochemical impedance (R_ct), Tafel slope and electrochemical active surface areas are 22.38 Ω, 63.8 mV dec⁻¹, and 707.5 cm⁻², respectively. The optimized NiMo-P/S hybrid provides more active sites and reaction areas along with good stability, which is conducive to promoting the kinetics of the oxygen evolution reaction.