Hybrid Metal-Boron Diatomic Site Embedded in C2N 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 (CO2RR) is explored on M@X-C2N (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 CO2RR especially C-C coupling. Among metal-boron DACs studies, Fe@B-C2N (mu = 2 mu(B)) exhibits the lowest free energy barrier of 0.17 eV in C-C coupling whereas Ni@B-C2N (mu = 0 mu(B)) 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 CO2RR. Fe@B-C2N is predicted as the promising catalyst for CO2RR towards C2+ products owing partially to its enhanced spin state. The findings can enrich the design strategy of electrocatalysts normally running at ambient conditions.

Automated summary

This study investigates the application of double-atom catalysts in CO2 reduction and demonstrates that hybrid M-B dual-atom centers can outperform single or double-M centers. Fe@B-C2N is predicted as a promising catalyst for the development of C2+ products.