Three-Dimensional Carbon Electrocatalysts for CO2 or CO Reduction
A challenge in the electrochemical CO2 reduction reaction (CO2RR) is the lack of efficient and selective electrocatalysts to valuable chemicals. Hydrocarbons and valuable chemicals from the CO2RR have primarily been observed on metallic Cu. Here, 3D carbon electrocatalysts (diporphyrin molecules; i.e., Pacman) have been investigated as potential CO2RR electrocatalysts using density functional theory simulations. This work presents a molecular-level engineering strategy for the development of electrocatalysts toward hydrocarbons. The introduction of a second metal center in the diporphyrins on one hand serves as a proton transfer or CO adsorption site, providing the possibility for the formation of C–H and C–C bonds. On the other hand, the second metal center selectively stabilizes key intermediates like *CH2O, *OCH3, and *OCCHOH, leading to CH4 and C2 species production. It has been found that Pacman (Pac) with Mn or Fe is able to produce CH4. Furthermore, Pac-CoNi, Pac-CoCu, and Pac-CoCo with pyridine coordination catalysts generate CH3OH, while Pac-CoCo might enable C–C coupling, forming C2 species.