Abstract
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•A series of Ni based single site metal catalysts (SSMCs) were successfully synthesized.•The pore structure of SSMCs was tuned via altering the silica source as the precursor of SiO2 template for the generation of carbon spheres.•The nanoarchitecture effect of carbon spheres for the generation of Ni-N single sites and catalytic activity for CO2 reduction were investigated.•Solid microporous carbon sphere was favorable for the generation of atomic Ni sites in SSMCs.•Hollow mesoporous structures enhanced the diffusion of CO2 and improved turnover frequencies value of per Ni site for CO2RR to CO.
Single-site metal catalysts (SSMCs) with high activity and stability have been widely applied as electrocatalysts for electrochemical CO2 reduction reaction (CO2RR) 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 CO2RR. 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 CO2 and improve the catalytic activity of per Ni site toward CO2RR process. Thus, Ni-N/C–H-Meso shows the highest turnover frequencies (TOF) value for CO2RR to CO. This study provides a SSMCs design protocol for investigation the SSMCs correlation of structure and properties toward electrochemical conversions.