Pore-structure-directed CO₂ electroreduction to formate on SnO₂/C catalysts

Electrochemical reduction of carbon dioxide (CO₂) to value-added chemicals and fuels has attracted great interest, although it suffers from low energy efficiency and selectivity. Herein, we discover that the pore structure of a supported catalyst significantly affects the products and efficiency of the electrochemical CO₂ reduction reaction (CO₂RR). Three-dimensional (3D) porous carbon (PC) sheets with abundant micropores and macropores and mesopore-dominant activated carbon (AC) have been used to construct electrocatalysts with uniformly dispersed SnO₂ nanoparticles. SnO₂/PC exhibits efficient formate production from the electrochemical CO₂RR with a high faradaic efficiency of 92% and partial current density of 29 mA cm⁻² at −0.86 V, ranking as a top-tier Sn-based catalyst. Importantly, systematic investigation and comparison with SnO₂/AC show that the space-confinement effect of micropores enhances CO₂RR selectivity towards formate by inhibiting proton transfer to active sites and thus suppressing the HER process, while the 3D sheet structure with abundant macropores provides mass and charge transport highways, making more active sites accessible for an effective CO₂RR and thus a larger current density. These findings shed light on the design of efficient electrocatalysts via engineering pore structures for diverse applications.