CO2 Activation and Electrochemical Reduction to CH3OH via Charge Modulation on Defect-Induced Free-Standing Bilayer Borophene

Activation and electrochemical reduction of CO₂ on the two-dimensional (2D) catalytic surface are limited by the highly stable C═O bond, high overpotential, and selectivity. Herein, we have investigated point defects in bilayer borophene (BL-B) to explore their influence on the activation of CO₂ and reduction to CH₃OH through charge modulation. The study shows that defect-induced bilayer borophene (BL-B-Def-1) activates CO₂ at a charge density of 5.12 × 10¹⁴ e^–/cm². Frontier molecular orbitals (FMOs) and p-band centers revealed the underlying reason for CO₂ activation over BL-B-Def-1 with extra electrons introduced. The catalytic activity of BL-B-Def-1 was studied via computational hydrogen electrode (CHE) with the charge-neutral method (CNM) and the constant potential method (CPM). The CNM assumed the catalyst was a constant or zero-charged system and ignored the effect of applied potential. However, the CPM charged the catalyst using the applied potential to meet its Fermi level. The predicted reaction pathways reveal that BL-B-Def-1 selectively reduces CO₂ to CH₃OH, with an overpotential (η) of 0.63 and 1.0 V, according to the CNM and CPM, respectively. Thus, our findings may help to develop catalysts for charge-controlled CO₂ activation and reduction and to understand the influence of applied potential on electrochemical processes.