Boosting CO2 Activation and Reduction by Engineering the Electronic Structure of Graphitic Carbon Nitride through Transition Metal-Free Single-Atom Functionalization

In recent years, electrochemical reduction of CO2 to high-value chemicals and fuels using carbon-based two-dimensional materials has emerged as a promising alternative for reducing the atmospheric CO2 levels and addressing global energy challenges. However, rationally tuning the electronic structure of these materials for optimizing their catalytic performance remains a great challenge. Herein, using first-principles simulations, we investigate the electronic and catalytic properties of the single atom (SA)-functionalized graphitic carbon nitride (g-C2N) monolayer for CO2 activation and reduction. Our results reveal that SA substitution leads to effective activation and capture of CO2. In-depth electronic structure analysis based on the crystal orbital Hamilton population (COHP) and integrated density of states unraveled the atomic-level details of the interaction of CO2 with the SA-substituted monolayers. Furthermore, the simulated reaction pathways demonstrate that the Al-SAC is highly proficient for CO2 conversion to HCOOH, whereas the B-SAC reduces CO2 to CH3OH with a record-low limiting potential of -0.45 V. In addition, the Al-and B-SACs effectively suppress the competitive hydrogen evolution reaction (HER), making CO2 reduction highly selective on these catalysts. Furthermore, the small CH3OH desorption energy of 0.73 eV on the B-SAC makes it a suitable candidate for CO2 reduction to methanol. Thus, our findings not only provide theoretical guidance for accelerating the design of new and promising catalysts for CO2 reduction but also elucidate the structure-activity correlations.