TM 2 -B 2 Quadruple Active Sites Supported on a Defective C 3 N Monolayer as Catalyst for the Electrochemical CO 2 Reduction: A Theoretical Perspective.

Developing high-performance electrocatalysts for the CO 2 reduction reaction (CO 2 RR) holds great potential to mitigate the depletion of fossil feedstocks and abate the emission of CO 2 . In this contribution, using density functional theory calculations, we systematically investigated the CO 2 RR performance catalyzed by TM 2 -B 2 (TM=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu) supported on a defective C 3 N monolayer (V-C 3 N). Through the screening in terms of stability of catalyst, activity towards CO 2 adsorption, and selectivity against hydrogen evolution reaction, Mn 2 -, Fe 2 -, Co 2 -, and Ni 2 -B 2 @V-C 3 N were demonstrated to be a highly promising CO 2 RR electrocatalyst. Due to quadruple active sites, these candidates can adsorb two or three CO 2 molecules. Strikingly, different products, distributing from C 1 to C 2+ , 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 C 2+ 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 ΔE C -0.4 ΔE O =-1.77 eV (ΔE C /ΔE 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 CO 2 RR and for the synthesis of C 2+ compounds.