A first-principles theoretical study on the TM@χ3-borophene single-atom-catalysts for electrochemical CO2 reduction reaction

We present a theoretical design study of single-atom catalysts (Fe, Co, Ni, and Cu) supported on χ 3 -type borophene for electrochemical CO 2 reduction (eCO 2 RR). Our density functional theory calculations reveal that Ni and Co exhibit excellent activity and stability toward formate production, with Ni showing the lowest rate-determining energy barrier of 0.12 eV, while Co’s barrier further decreases to 0.09 eV upon solvation. Cu displays unique selectivity for the *OCHO pathway, though its performance is more sensitive to solvation effects. Remarkably, a pronounced hydrogen spillover effect is identified in the Fe system, which not only reduces the formate barrier from 0.58 to 0.38 eV by modulating interfacial hydrogen distribution but also suppresses deep reduction routes, demonstrating dual regulatory roles in activity and selectivity. Competitive hydrogen evolution analysis indicates that Cu and Ni are less affected by HER, while the spillover behavior critically governs Fe’s catalytic performance. These findings provide theoretical insights for designing borophene-based single-atom electrocatalysts for CO 2 RR.