Unveiling fundamental first-principles insights into single-atom transition metal photocatalysts for carbon dioxide reduction

Unraveling single-atom photocatalysts for efficient photocatalytic CO 2 reduction reaction through a comprehensive computational screening based on density functional theory calculations. • Transition-metal (TM) elements investigated for single-atom photocatalysts (SAPs). • Selectivity is found to be correlated with the degree of electron transfers between TM atoms and SAPs. • Partially occupied and empty states are crucial for active CO 2 activation. The search for new single-atom photocatalysts (SAPs) has garnered significant focus for CO 2 reduction reaction (CO 2 RR) due to their maximum atom utilization efficiency. However, the rational design of SAPs remains elusive due to the lack of fundamental understanding behind the dynamic electron transfer between the anchored atoms and the semiconductor support. Herein, density functional theory calculations were performed to study the SAPs constituting transition metal (TM) in graphitic carbon nitride with a stoichiometry of C 6 N 6 (gC 6 N 6 ). A total of 26 single-atom elements from the TM group were investigated in this work. The in-depth analysis demonstrates that the selectivity for CO 2 RR over hydrogen evolution reaction (HER) is highly correlated with the degree of electrons transfer between the single TM atom and gC 6 N 6 . The coexistence of partially occupied states and empty states is essential for active CO 2 adsorption for these SAPs. Overall, the findings from this work will steer experimental progress towards the design of efficient SAPs for CO 2 RR.