Sulfur-Decorated Ni-N-C Catalyst for Electrocatalytic CO₂ Reduction with Near 100 % CO Selectivity

Developing highly efficient electrocatalysts for electrochemical CO₂ reduction (ECR) to value-added products is important for CO₂ conversion and utilization technologies. In this work, a sulfur-doped Ni-N-C catalyst is fabricated through a facile ion-adsorption and pyrolysis treatment. The resulting Ni-NS-C catalyst exhibits higher activity in ECR to CO than S-free Ni-N-C, yielding a current density of 20.5 mA cm^-2 under -0.80 V versus a reversible hydrogen electrode (vs. RHE) and a maximum CO faradaic efficiency of nearly 100 %. It also displays excellent stability with negligible activity decay after electrocatalysis for 19 h. A combination of experimental investigations and DFT calculations demonstrates that the high activity and selectivity of ECR to CO is due to a synergistic effect of the S and Ni-N_X moieties. This work provides insights for the design and synthesis of nonmetal atom-decorated M-N-C-based ECR electrocatalysts.