Mechanically stable defective Mo2TiX2O2 MXenes as potential electrocatalyst for CO2 reduction toward methanol production

The electrochemical conversion of carbon dioxide (CO 2 ) into liquid fuels offers a sustainable pathway to mitigate greenhouse emissions while storing renewable energy in chemical form. MXenes are promising candidates for this reaction due to their exceptional conductivity and tunable surface chemistry. Herein, we applied density functional theory to reveal that defect-engineered double transition metal (DTM) MXenes can exhibit remarkable catalytic enhancement. The formation of a mechanically stable metal‑oxygen-vacancy pair center in Mo 2 TiC 2 O 2 is energetically allowed, which can significantly lower the overpotential for methanol formation to only 0.46 V. The reaction proceeds via the formate pathway, where the vacancy pair center acts as a Lewis acidic site that strongly anchors the nucleophilic oxygen atom of CO 2 . This acid-based interplay drives efficient activation, stabilizes key intermediates, and suppresses the competing hydrogen evolution reaction. These findings position defective DTM MXenes as highly promising electrocatalysts and underscore the pivotal role of defect engineering in tailoring MXenes for efficient CO 2 conversion.