Impact of Pore Structure on Electrochemical Reduction of Carbon Dioxide in Iron- and Nitrogen-Doped Carbon Materials: Solid–Liquid Interface Versus Solid–Gas–Liquid Triple-Phase Boundary

The effect of porosity on the interface microenvironment and catalytic performance of carbon dioxide reduction reaction (CO2RR) is still unclear for iron- and nitrogen-doped carbon-based (Fe/N/C) materials, and previous studies mainly focus on aqueous electrode test conditions rather than a practical working environment. Herein, several Fe/N/C-based catalysts with very different pore structures were prepared and compared to understand how the surface area and micropores affect the CO2RR between aqueous electrode test and practical working conditions with a solid–gas–liquid triple-phase boundary. The apparent current density correlates positively to the surface area in both test conditions. The onset current density where hydrogen evolution reaction starts is irrelevant to the micropore fraction in the aqueous electrode test but correlates negatively to the micropore fraction in a practical working condition. The inconsistency is attributed to different reaction interfaces in both cases, resulting in different interface microenvironments in different pore size ranges. This work helps in designing porous electrocatalysts for CO2RR or beyond.