Identification of non-metal single atomic phosphorus active sites for the CO2 reduction reaction

Heterogeneous single-atom catalysts (SACs) show maximum atom utilization efficiency and great product selectivity in various catalytic reactions. To date, SACs have been intensively investigated with various metal active centers, while non-metal active centers are rarely elucidated, owing to the challenges in identifying non-metal active sites and reaction pathways. Herein, we develop a non-metal single-atom catalyst composed of high-density, isolated phosphorus atoms anchored at the edge of graphene as a robust electrocatalyst for the CO2 reduction reaction. The CO2 molecular activation and the electrochemical CO2 reduction pathways at P atomic sites are identified by combining both in situ/ex situ experiments and quantum-chemical theoretical study. Our work not only extends the definition of SACs to a non-metal catalytic center, but also offers unique insights into the non-metal active site geometric and structural transformation during the CO2 reduction reaction.