Theoretical study on electroreduction of CO2 to multi-carbon compounds catalyzed by Mo-based two-dimensional carbon-rich conjugated frameworks in tandem

Electrocatalytic reduction of CO2 to multi-carbon compounds, such as n-propanol, α-olefins, and Dimethyl carbonate (DMC), has been widely considered an effective strategy to address excessive CO2 emissions. However, enhancing reaction activity and selectivity is still challenging. In this work, a tandem catalyst built on Mo-based two-dimensional carbon-rich conjugated frameworks (2D CCFs) that has unique catalytic sites is introduced, which can efficiently convert and stabilize both C1 and C2 intermediates simultaneously. And, the reaction mechanisms and complex intermediates involved in the reduction of CO2 to n-propanol, α-olefins, and DMC on Mo-based 2D CCFs have been thoroughly investigated. Based on density functional theory (DFT) calculations, Mo-Cr-Pc-Ni-O-CCFs, Mo-Cr-Pc-Mo-S-CCFs, and Mo-Mn-Pc-Co-TPP-CCFs in various catalysts are screened out because of their better CO2 adsorption capacity and outstanding catalytic activity in the CO2 reduction process (CO2RR). In addition, they can efficiently inhibit hydrogen evolution reaction (HER) while simultaneously promoting multiple C-C coupling, which enhances the electrosynthesis of n-propanol, α-olefins, and DMC. Comparing the d-band values and CO2 adsorption capacities of Fe-based and Mo-based catalysts also reveals that Mo-based catalysts have higher catalytic activity and selectivity, which can be attributed to orbital hybridization and an electron donation-feedback mechanism. It effectively activates CO2 molecules and causes them to be stably adsorbed on the catalyst. This research offers a theoretical foundation for the production of multi-carbon compounds as well as a reasonable guidance for the design of innovative Mo-based catalysts.