Deciphering Mesopore-Augmented CO₂ Electroreduction over Atomically Dispersed Fe–N-doped Carbon Catalysts

Mesoporous metal–nitrogen-doped carbons (M–N–C) have shown remarkable performance as catalysts for electrochemical CO₂ reduction. However, the current understanding of the roles of mesopores in M–N–C-catalyzed CO₂ reduction has been insufficient and imprecise due to the overlooked and intertwined influences of various structural factors on mass transport and the catalyst microenvironment. In this work, we have decoupled the impacts of mesopores in this process by designing Fe–N–C with solely altered pore structures. We found that the mesopore-rich catalyst surpassed its microporous counterpart in the overall reaction rate but unusually fell short in CO selectivity. Our experiments and modulation uncovered that the abundance of mesopores on the catalyst surface facilitated CO₂ diffusion to active sites and thereby improved the CO production rate; however, the increased CO₂ transport buffered the local pH surrounding active sites, which increased H₂ generation and induced a relative decrease in CO selectivity for the mesopore-rich Fe–N–C catalyst.