The Deep Understanding into the Promoted Carbon Dioxide Electroreduction of ZIF-8-Derived Single-Atom Catalysts by the Simple Grinding Process

Zeolitic imidazolate framework (ZIF-8)-derived single-atom catalysts (SACs) are widely studied in many catalytic reactions such as hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and CO2 reduction reactions (CO2RR). Grinding procedures involved in the synthesis of ZIF-8-derived SACs could affect the catalytic performance but are less evaluated in the literature. Herein, a series of ZIF-8-derived cobalt SACs (C-Co-ZIFs) with different grinding processes to investigate the impact of the grinding degrees on the performance of the electrochemical reduction reaction of CO2 (ECO2RR) is presented. The moderate grinding process affords a boost in CO Faradaic efficiency (FE, around 15% higher than that of the original C-Co-ZIF) and the highest current densities among all the samples. The variations in the electronic structure of the Co active sites in the ground catalysts are confirmed by X-Ray absorption spectroscopy (XAS) and X-Ray emission spectroscopy (XES) for improved catalytic performance. The increased micropores in the moderately ground catalyst provide more exposed active sites while the increased meso- and macropores promote the mass transfer, benefiting the ECO2RR performance. It suggests that the impact of grinding processes on the synthesis of ZIF-8-derived SACs should be considered for the evaluation of the catalytic performance.

Automated summary

The study demonstrates that moderate grinding processes can enhance CO Faradaic efficiency and current density in the electrochemical reduction reaction of CO2 (ECO2RR). Changes in the electronic structure of cobalt active sites in the ground catalysts are confirmed by X-ray spectroscopy, improving catalytic performance.