Surface Hydroxylation Mechanism of Zr2X(OH)2 (X = C, N, or B) MXenes: A Promising Catalyst for CO

Electrocatalytic transformation of CO2 to formic acid is typically realized via bi-hydrogenation process, which is remarkably challenging because of high thermodynamic stability and chemical inertness of the intermediate. Here, we explored the surface hydroxylation mechanism for CO2 conversion into formic acid over OH-terminated MXenes that can effectively circumvent the thermodynamic sink of the conventional bi-hydrogenation process by capturing additional hydrogen from the surface. The observed unique CO2RR activity can be attributed to the reactive H atom on the OH-terminated MXenes. The facile capture of (H) from OH-terminated MXenes confirm the viability of surface-hydroxylation mechanism. In addition, the ultra low work functions (1.72–2.27 eV) of such materials demonstrate the significance of functional groups in deciding the surface electrostatic potential of MXenes during the etching process. Overall, the present study bypass the thermodynamic constraints hampering the formation of formic acid by eliminating the intermediate step in the CO2 hydrogenation reaction and is likely to have considerable implications in the fields of catalytic chemistry and CO2 conversion.