Unlocking Exceptional CO₂ Reduction Selectivity at Neutral Conditions: A First-Principles Study on Chlorinated Single Iron Doped Graphitic Carbon Nitride

The electrochemical reduction of carbon dioxide (CO2RR) to useful fuels and chemicals using renewable energy sources presents a promising strategy for addressing energy security and environmental challenges. Single-metal atom catalysts have emerged as appealing alternatives due to their high efficiency in overcoming limitations associated with traditional metal nanocatalysts. This comprehensive study focuses on fine-tuning chlorinated single-atom-based active sites on a graphitic carbon nitride (g-C3N4) monolayer to achieve absolute selectivity for HCOOH. Previous research has demonstrated that halogenation significantly suppresses the hydrogen evolution reaction, which competes with the CO2RR. To achieve selectivity for a single product among all reduced products, the chemical environment of the catalyst was tuned to neutral conditions. Our results indicate that the catalyst exhibited higher selectivity for HCOOH, with a significantly low onset potential and a wide potential range where HCOOH selectivity was maintained at the FeCl site at pH 7 compared to the acidic region. These findings highlight the FeCl active site of FeCl-decorated g-C3N4 as a highly efficient and selective electrocatalyst for the CO2RR. The insights gained from our study offer valuable directions for designing new CO2RR catalysts with improved selectivity and efficiencies.