Theoretical study on Electrocatalytic Reduction of CO2 over Co based nitrogen doped graphene nanolayer supported diatomic catalyst

Abstract

Dual–atom catalysts (DACs) exhibit significant potential in the electrochemical reduction of carbon dioxide (CO2RR) for future energy regeneration and greenhouse effect mitigation. However, understanding the mechanism underlying DACs in CO2RR and regulating their selectivity toward C1 versus C2 products remain challenging. Herein, combined with density functional theory (DFT) calculations, we designed two types of DACs with distinct configurations and investigated their selectivity for C1 and C2 products. Through calculations of formation energy and adsorption energy, the a-configuration was found to possess higher structural stability. Thermodynamic analysis of key intermediates revealed that all six M1N3-M2N3@NGr-a catalysts tend to generate C2 products, in contrast to M1N3-M2N3@NGr-s. Subsequently, the detailed mechanism of CO2 reduction over M1N3-M2N3@NGr-a was systematically explored. The results indicate that three distinct C-C coupling pathways were identified via thermodynamic analysis. CoN3-CoN3@NGr-a, CoN3-CrN3@NGr-a, and CoN3-NiN3@NGr-a show a preference for ethanol formation, while CoN3-CuN3@NGr-a, CoN3-FeN3@NGr-a, and CoN3-MnN3@NGr-a favor ethylene production. Among these, CoN3-NiN3@NGr-a exhibits the optimal catalytic activity for ethanol with a limiting potential (UL) of only -0.68 V, whereas CoN3-FeN3@NGr-a demonstrates the highest ethylene activity with a UL of -0.36 V. Finally, the system compares the differences of Co-M diatomic sites on the C1/C2 pathway, and divides the specific mechanisms of these three reaction pathways into two categories, proposing "two types of selective control mechanisms". The first type is primarily determined by the catalyst's oxygen adsorption ability: stronger O adsorption favors ethylene formation, while weaker adsorption promotes ethanol production. The second type is governed by the catalyst's ethylene adsorption strength: weaker ethylene adsorption is more conducive to ethylene generation.