Synergetic effect of phosphorus-dopant and graphene-covering layer on hydrogen evolution activity and durability of NiCo₂S₄ electrocatalysts

The investigation of highly conductive and stable non-noble metal electrocatalysts is imperative for promoting the hydrogen economy. Herein, we employed het-eroatom-doping and graphene-covering techniques to enhance the electronic properties of NiCo₂S₄ (NCS) yolk-shell microspheres, boosting their resistance to H₂O and O₂ corrosion in acidic environments. Based on the results of density functional theory (DFT) simulations and comprehensive characterizations, P heteroatom introduction into NCS was found to expedite electron transfer from bulk to surface, reducing the barrier for the hydrogen evolution reaction (HER) on neighboring active S sites. DFT-calculated energy barriers and X-ray photoelectron spectrometer analysis substantiated that the reduced graphene oxide (rGO)-covering layer played a vital role by facilitating proton permeability in HER while hindering H₂O and O₂ molecule penetration. By leveraging charge transfer and mass transfer, a balanced catalyst with high activity and corrosion resistance was achieved. The optimized P-NCS/rGO catalyst exhibited a current density of 10 mA cm⁻² at a low overpotential of 70 mV, demonstrating excellent durability over 80 h. This study exemplified the rational design of graphene-covered sulfide catalysts, enhancing electrocatalyst performance through the regulation of electronic structures and proton/molecule penetration. [Figure not available: see fulltext.]