Electroreduction of CO₂ to CO on a Mesoporous Carbon Catalyst with Progressively Removed Nitrogen Moieties

In this study, we prepared nitrogen-removed mesoporous carbon (NRMC) catalysts by applying various heat treatments to nitrogen-doped mesoporous carbon (NMC), which were applied as novel electrocatalysts for CO₂ reduction reaction (CO₂RR). With the nitrogen moieties being progressively removed, the NRMC catalysts exhibited enhanced CO generation from CO₂RR, whereas the competing hydrogen evolution reaction (HER) has been suppressed. Through suitable annealing treatment, the defect-rich NRMC catalyst is able to convert CO₂ to CO with a Faradaic efficiency (FE_CO) of ∼80% and a partial current density for CO (j_CO) of -2.9 mA cm^-2 at an applied overpotential of 490 mV. Density functional theory (DFT) calculations further revealed the active sites within NRMC catalysts were the defects generated by N removal, which lowered the energy barriers for CO₂RR and will not be passivated by hydrogen. These findings provide design guidelines to develop efficient carbon-based catalysts that can display metal-like, and even better, performances for potential scalable CO₂RR to fuels and chemicals.