Hollow Mesoporous Carbon Sphere Loaded Ni-N Single-Atom: Support Structure Study for CO Electrocatalytic Reduction Catalyst.

Single-atom catalysts have become a hot spot because of the high atom utilization efficiency and excellent activity. However, the effect of the support structure in the single-atom catalyst is often unnoticed in the catalytic process. Herein, a series of carbon spheres supported Ni-N single-atom catalysts with different support structures are successfully synthesized by the fine adjustment of synthetic conditions. The hollow mesoporous carbon spheres supported Ni-N catalyst (Ni/HMCS-3-800) exhibits superior catalytic activity toward the electrocatalytic CO reduction reaction (CO RR). The Faradaic efficiency toward CO is high to 95% at the potential range from -0.7 to -1.1 V versus reversible hydrogen electrode and the turnover frequency value is high up to 15 608 h . More importantly, the effect of the geometrical structures of carbon support on the CO RR performance is studied intensively. The shell thickness and compactness of carbon spheres regulate the chemical environment of the doped-N species in the carbon skeleton effectively and promote CO molecule activation. Additionally, the optimized mesopore size is beneficial to improve diffusion and overflow of the substance, which enhances the CO adsorption capacity greatly. This work provides a new consideration for promoting the catalytic performance of single-atom catalysts.