First-principles Investigation of Single 3d Transition Metals Doping Graphene Vacancies for CO2 Electroreduction

Among all options of carbon neutrality, conversion of CO2 into valuable chemicals by electrocatalytic reduction exhibit outstanding performance. However, due to the numerous products and complex pathways of CO2 electrocatalytic reduction, the exact factors affecting the activity of CO2 electrocatalytic reduction have not yet been identified. In addition, the CO2 electrocatalytic reduction process is often accompanied by hydrogen evolution reaction (HER). Therefore, it is still challenging to design a catalyst with high selectivity and high activity for specific product. Herein, this study systematically investigated the potential of 3d transition metal-based single-atom catalysts (SACs) positioned at graphene single vacancies (TM@C-SV), as well as double vacancies (TM@C-DV), for the CO2 reduction reaction (CO2RR) using first-principles. The exploration encompassed substrate stability, CO2 adsorption, and the HER as the main competing reaction. Through the careful screening of 20 catalysts formed by Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn doped graphene defects, several promising catalysts were identified: Sc@C-SV situated on graphene single vacancies, Sc@C-DV and Ti@C-DV situated on graphene double vacancies. They could not only effectively adsorb CO2 molecules, but also inhibit HER, the main competing reaction. In assessing their performance in CO2RR, all exhibited selectivity toward HCOOH. Notably, Sc@C-DV demonstrated the best selectivity, requiring the lowest Delta G (0.96 eV) for efficient CO2 conversion to HCOOH. Electronic structure analysis revealed that Sc@C-DV outperforms due to its optimal balance between Delta G of hydrogenation and the product desorption achieved through a moderate number of active electrons.