Electronic structure modulation of isolated Co-N4 electrocatalyst by sulfur for improved pH-universal hydrogen evolution reaction

Exploring an efficient platinum group metal (PGM) free electrocatalyst with superior activity and stability for hydrogen evolution reaction (HER) in a wide pH range is desirable for low-cost hydrogen production. Here, we report atomically dispersed cobalt on nitrogen and sulfur co-doped graphene (N-Co-S/G) for HER. Remarkably, the prepared N-Co-S/G electrocatalyst shows a small overpotential of 67.7 mV vs. reversible hydrogen electrode (RHE) at a current density of 10 mA cm(-2) and exceptional durability over 100 h at 10 mA cm(-2) under acidic conditions. Moreover, we found that the HER activity of N-Co-S/G is close to 20% Pt/C at all pH levels (0-14) and superior activity at high current density (>100 mA cm(-2)). Experimental and theoretical calculations reveal that the S atom in N-Co-S/G form Co-S bond, resulting new Co-N3S1 active site, which optimizes Gibbs free energy for hydrogen adsorption (Delta G(H)*) close to zero, while water adsorption and dissociation enhanced by S modulation for neutral and basic media HER.

Automated summary

N-Co-S/G is a novel nitrogen and sulfur co-doped graphene electrocatalyst that optimizes Gibbs free energy and enhances water adsorption and dissociation in neutral and alkaline media, displaying comparable or even superior activity to 20% Pt/C in hydrogen evolution reaction.