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

Abstract

Molybdenum carbide (Mo_xC) 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_xC(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_xC nanorods via carbonization, which exhibited decent electrocatalytic performance for the hydrogen evolution reaction (HER) by electrochemical water splitting. The NiCo–Mo_xC 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_xC, performed under controlled conditions, resulted in the formation of NiPS–CoPS–Mo_xC, which demonstrated superior HER performance than the precursor NiCo–Mo_xC 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.