Hybrid Metal-Boron Diatomic Site Embedded in C2 N Monolayer Promotes C-C Coupling in CO2 Electroreduction.

Double-atom catalyst (DAC) has gained much interest for its versatile tuning and synergistic effect of dual-atom active sites. Metal (M)-metal (M) diatomic sites, either homo- or heteronuclear, are typically researched. Hybrid metal-non-metal combined sites have rarely been studied and even the viability of such active sites are unknown. Herein, CO2 electroreduction (CO2 RR) is explored on M@X-C2 N (M = Fe, Co, Ni, and Cu; X = S, P, and B) which renders naturally generated M-X diatomic site. Using spin-polarized density functional theory coupled with computational hydrogen electrode model, it is demonstrated that the functionality of hybrid M-B dual-atom center is superior over that of a single- or double-M center in driving CO2 RR especially C-C coupling. Among metal-boron DACs studies, Fe@B-C2 N (μ = 2μB ) exhibits the lowest free energy barrier of 0.17 eV in C-C coupling whereas Ni@B-C2 N (μ = 0μB ) mainly produces CH4 with the lowest barrier of 0.42 eV. Hence, the electronic spin state of M can be particularly important in modulating selectivity and C-C coupling barrier in CO2 RR. Fe@B-C2 N is predicted as the promising catalyst for CO2 RR towards C2+ products owing partially to its enhanced spin state. The findings can enrich the design strategy of electrocatalysts normally running at ambient conditions.