Molybdenum carbide supported metal-organic framework-derived Ni, Co phosphosulphide heterostructures as efficient OER and HER catalysts.

Abstract

Molybdenum carbide (Mo _x C) has gained attention for water splitting due to its electronic structure resembling to Pt and have high electrochemical performance. We designed porous nanostructured phosphorus/sulfur co-doped Ni, Co phosphosulphide and molybdenum carbide heterostructures Mo _x C(Mo₂C-MoC) through confined carburization within a metal-organic framework (MOF) matrix combined with a phosphosulfurization strategy. Starting from a carbon source consisting of NiCo-MOF incorporating molybdenum trioxide, we prepared MOF-derived NiCo-Mo _x C nanorods via carbonization, which exhibited decent electrocatalytic performance for the hydrogen evolution reaction (HER) by electrochemical water splitting. The NiCo-Mo _x C showed low overpotentials of 153 mV and 157 mV vs. RHE at a current density of 10 mA cm^-2 in 0.5 M H₂SO₄ and 1 M KOH, respectively. Phosphosulfurization of NiCo-Mo _x C, performed under controlled conditions, resulted in the formation of NiPS-CoPS-Mo _x C, which demonstrated superior HER performance than the precursor NiCo-Mo _x C with overpotentials of 75.2 mV and 86.6 mV in 0.5 M H₂SO₄ and 1 M KOH, respectively and an overpotential of 184.5 mV at 10 mA cm^-2 for the oxygen evolution reaction (OER). The durability of the NCMCSP-based electrolyzer for the overall water splitting was evaluated by measuring the voltage over time at a constant current density of 20 mA cm^-2 for 12 h.