Pore Geometry and Nitrogen Doping Regulate Carbon-Source Transport Through Carbon Nanocage Shells for CO2 Electroreduction

Carbon nanocages provide confined reaction environments for CO2 reduction reaction (CO2RR), but carbon sources must first cross their microporous graphitic shells to reach encapsulated catalytic sites. Here, molecular dynamics simulations were used to elucidate carbon-source transport through through-layer pores (TLPs), representing the edge-rich vertical micropores formed across stacked graphene layers in carbon nanocages. We examined the effects of pore diameter, N-doping, and pore depth on the transport of CO2RR-relevant carbon species. Among the investigated structures, a 12.1 Å N-doped TLP achieved the highest area-normalized cross-pore transport ratio of 1.296 × 10−2 Å−2. N-doping preferentially enhanced neutral CO2 transport, while producing only limited improvements for bicarbonate and carbonate ions. This selectivity originates from strong CO2 interactions with N-containing pore-edge sites, which establish a CO2-enriched interfacial region and promote adsorption-assisted capture–transfer without persistent molecular trapping. N-doping reduces both resistance contributions, leading to an approximately 30.4% decrease in pore-mouth resistance and ~45% reduction in pore-interior resistance at pore depths of 17.0 Å. These results identify short, appropriately sized, and N-functionalized through-layer micropores as favorable architectures for delivering CO2 to confined catalysts, providing molecular design principles for carbon-nanocage nanoreactors for CO2RR.