TM2−B2 Quadruple Active Sites Supported on a Defective C3N Monolayer As Catalyst for the Electrochemical CO2 Reduction: A Theoretical Perspective

Developing high-performance electrocatalysts for the CO2 reduction reaction (CO2RR) holds great potential to mitigate the depletion of fossil feedstocks and abate the emission of CO2. In this contribution, using density functional theory calculations, we systematically investigated the CO2RR performance catalyzed by TM2-B-2 (TM=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu) supported on a defective C3N monolayer (V-C3N). Through the screening in terms of stability of catalyst, activity towards CO2 adsorption, and selectivity against hydrogen evolution reaction, Mn-2-, Fe-2-, Co-2-, and Ni-2-B-2@V-C3N were demonstrated to be a highly promising CO2RR electrocatalyst. Due to quadruple active sites, these candidates can adsorb two or three CO2 molecules. Strikingly, different products, distributing from C-1 to C2+, can be generated. The high activity originates from the synergistic effect of TM and B atoms, in which they serve as adsorption sites for the C- and O-species, respectively. The high selectivity towards C2+ products at the Fe-2-, and Ni-2-B-2 sites stems from moderate C adsorption strength but relatively weak O adsorption strength, in which a universal descriptor, that is, 0.6 Delta E-C-0.4 Delta E-O=-1.77 eV (Delta E-C/Delta E-O is the adsorption energy of C/O), was proposed. This work would offer a novel perspective for the design of high active electrocatalysts towards CO2RR and for the synthesis of C2+ compounds.