Preparation and insight into efficient catalytic properties at electronic/molecular level for metal sulfide modified carbon material

Metal sulfide modified carbon materials with wide application potential have recently attracted great attention in the fuel cells, owing to their efficient oxygen reduction reaction (ORR) performance. However, in-depth insight into their efficient catalytic properties at the electronic/molecular level is still a challenging issue. Here, we present the synthesis of a novel Co₉S₈@N/S–C composite catalyst, where Co₉S₈ nanoclusters are incorporated into an N/S-doped carbon matrix. The composite material also has highest half-wave potential of 0.846 V and largest limiting current density of −6.55 mA cm⁻² relative to N/S–C (0.802 V and −4.02 mA cm⁻²) and Pt/C (0.839 V and −5.46 mA cm⁻²). Using Co₉S₈@N/S–C as a model, density functional theory (DFT) calculations and molecular dynamics simulations were performed to explore the exceptional ORR catalytic performance of metal sulfide-modified carbon catalysts, revealing the underlying mechanisms at the electronic and molecular levels. The results demonstrate that Co₉S₈@N/S–C provides abundant metal active sites, reduces the electronic work function, enhances conductivity, and lowers the ORR reaction energy barrier through strong interfacial interactions. Meanwhile, the oxygen diffusion coefficient near the interface between Co₉S₈@N/S–C and potassium hydroxide solution is significantly increased, and the ability to adsorb oxygen molecules is also improved. As a result, the excellent catalytic ORR performance is obtained on the Co₉S₈@N/S–C composite catalyst. This work furnishes a demonstration effect model for the tailor-made design and fabrication of metal sulfide modified carbon materials in the catalytic applications.