The search for efficient catalysts for the electrochemical reduction of CO2 into value-added fuels is ongoing. In this work, we investigate Mo2B, a two-dimensional (2D) MBene and an extension of the MXene family, as a potential catalyst for CO2 capture and reduction using first-principles calculations. In this study, the CO2 capture properties of pristine 2D Mo2B in the 2H phase, along with its functionalized derivatives Mo2BX2 (X = O, OH, H), are systematically evaluated. We found that Mo2BX2 is inert toward CO2 capture, while pristine Mo2B interacts strongly and effectively activates CO2 with a stronger adsorption energy of −2.47 eV. Projected density of states and Bader charge analyses reveal that pristine Mo2B exhibits a stronger CO2 capture affinity, which can be attributed to the high population of Mo dz2 states near the Fermi level and the substantial charge donation (∼0.31e) from each surrounding Mo atom to the O atoms of CO2. This substantial Mo-to-O charge transfer weakens the C═O bonds, thereby facilitating CO2 activation and the subsequent reduction mechanism. In contrast, surface functionalization weakens the direct interaction between Mo and CO2, leading to suppressed charge transfer. Electronic structure analysis also reveals that the stronger C═O interaction on Mo2B is primarily governed by the Mo dz2 and C/O pz orbitals of CO2. Further analysis of the reduction pathways indicates that captured CO2 can be converted to CH4, with the CO → HCO step exhibiting the highest Gibbs free energy change. The low limiting potential of Mo2B (−0.570 V), in comparison with the Gibbs free energy of H adsorption (−0.63 eV), suggests higher selectivity toward the CO2-to-CH4 conversion over the competing hydrogen evolution reaction. These results highlight Mo2B as a promising candidate for the electrochemical reduction of CO2. These theoretical insights may pave the way for the experimental realization of MBenes tailored for the CO2 reduction reactions.
Yadav et al. (Fri,) studied this question.