The structure–activity correlation of single-site Ni catalysts dispersed onto porous carbon spheres toward electrochemical CO2 reduction

Single-site metal catalysts (SSMCs) with high activity and stability have been widely applied as electrocatalysts for electrochemical CO 2 reduction reaction (CO 2 RR) process. However, it remains challenging for precise controlling the nanoarchitectures and atomic metal sites of SSMCs to investigate their corresponding structural and related catalytic properties toward CO 2 RR. In this work, four categories of Ni based SSMCs with different nanoarchitectures were successfully synthesized, including Ni-N doped solid carbon spheres with micropore (Ni-N/C-S-Micro), Ni-N doped hollow carbon spheres with micropore (Ni-N/C–H-Micro), Ni-N doped hollow carbon spheres with mesopore (Ni-N/C–H-Meso), and Ni-N doped hollow carbon spheres with micropore and mesopore (Ni-N/C–H-Micro/Meso). Ni-N/C-S-Micro and Ni-N/C–H-Micro were favorable for the generation of atomic Ni sites in SSMCs, resulting in higher loading amount of Ni, while Ni-N/C–H-Meso with open structure leads to the aggregation of Ni species during pyrolysis. In comparison with Ni-N/C-S-Micro, carbon spheres with hollow and mesoporous structures can enhance the diffusion of CO 2 and improve the catalytic activity of per Ni site toward CO 2 RR process. Thus, Ni-N/C–H-Meso shows the highest turnover frequencies (TOF) value for CO 2 RR to CO. This study provides a SSMCs design protocol for investigation the SSMCs correlation of structure and properties toward electrochemical conversions.