Verifying the efficient functional N species of metal-free N-doped carbons for CO2-to-CO electrochemical conversion using zeolite-templated carbons with N species tuned by a recarbonization treatment

Abstract

The electrochemical reduction reaction of carbon dioxide is expected as a potential solution to reducing CO₂ emission and providing value-added chemicals. Carbon monoxide (CO) is a fundamental chemical precursor for industrially important reactions. Therefore, metal-free heteroatom-doped carbon materials have attracted increasing attention as electrocatalysts for CO₂-to-CO conversion. Nitrogen (N)-doped carbon is a promising alternative catalyst. The introduction of N atoms modifies the electronic and chemical structures and leads to enhanced electrocatalytic performance. While the bonding states of N species influence the CO₂RR activity has been discussed, no reports have demonstrated the relationship between the bonding state and activity by dividing graphitic N into two configurations (valley N and center N). In this study, we have controlled the local chemical state of N species of N-doped carbon materials through the combination of a zeolite templating method and a recarbonization treatment to investigate the effective functional N species for CO₂-to-CO conversion. When the recarbonization temperature increased, the content of valley N increased, and the CO₂-to-CO conversion was enhanced. The highest faradaic efficiency of CO was 76%. DFT calculations revealed that valley N and the edge site C atom adjacent to valley N stabilized *COOH intermediate, contributing to the enhanced CO₂-to-CO conversion.