A nanohybrid consisting of NiPS₃ nanoparticles coupled with defective graphene as a pH-universal electrocatalyst for efficient hydrogen evolution

We report metallic NiPS₃ nanoparticles decorated defective graphene (NiPS₃@DG) as an efficient and durable electrocatalyst for the hydrogen evolution reaction (HER) at all pH values. The nanohybrids exhibited impressive low overpotentials (η10) of 73, 97, and 99 mV at -10 mA cm^-2 in acidic (pH ∼ 0), neutral (pH 7) and alkaline (pH 14) electrolyte, respectively, which competes with (or even surpasses) commercial Pt/C (20 wt%) catalysts. Furthermore, the NiPS₃@DG electrocatalyst displayed long-term stability and durability in a pH-universal medium as confirmed by a negligible decay in catalytic performances after 40 h of continuous working and 5000 voltammetric sweeping cycles. Theoretical calculations further revealed that the optimal free energy of the hydrogen adsorption process (which stems from a synergistic effect of S and P) provides tremendous contribution to the pH-universal HER process. The design strategy of the di-anion nanohybrid electrocatalyst highlights a new avenue for preparing cost-effective and pH-universal electrocatalysts.