Theoretical Identification of Highly Active Mo 2 B (MBenes) toward CO 2 Capture and Reduction

The search for efficient catalysts for the electrochemical reduction of CO 2 into value-added fuels is ongoing. In this work, we investigate Mo 2 B, a two-dimensional (2D) MBene and an extension of the MXene family, as a potential catalyst for CO 2 capture and reduction using first-principles calculations. In this study, the CO 2 capture properties of pristine 2D Mo 2 B in the 2H phase, along with its functionalized derivatives Mo 2 BX 2 (X = O, OH, H), are systematically evaluated. We found that Mo 2 BX 2 is inert toward CO 2 capture, while pristine Mo 2 B interacts strongly and effectively activates CO 2 with a stronger adsorption energy of −2.47 eV. Projected density of states and Bader charge analyses reveal that pristine Mo 2 B exhibits a stronger CO 2 capture affinity, which can be attributed to the high population of Mo d z 2 states near the Fermi level and the substantial charge donation (∼0.31e) from each surrounding Mo atom to the O atoms of CO 2 . This substantial Mo-to-O charge transfer weakens the C═O bonds, thereby facilitating CO 2 activation and the subsequent reduction mechanism. In contrast, surface functionalization weakens the direct interaction between Mo and CO 2, leading to suppressed charge transfer. Electronic structure analysis also reveals that the stronger C═O interaction on Mo 2 B is primarily governed by the Mo d z 2 and C/O p z orbitals of CO 2 . Further analysis of the reduction pathways indicates that captured CO 2 can be converted to CH 4, with the CO → HCO step exhibiting the highest Gibbs free energy change. The low limiting potential of Mo 2 B (−0.570 V), in comparison with the Gibbs free energy of H adsorption (−0.63 eV), suggests higher selectivity toward the CO 2 -to-CH 4 conversion over the competing hydrogen evolution reaction. These results highlight Mo 2 B as a promising candidate for the electrochemical reduction of CO 2 . These theoretical insights may pave the way for the experimental realization of MBenes tailored for the CO 2 reduction reactions.