Catalytic Effect on CO₂ Electroreduction by Hydroxyl-Terminated Two-Dimensional MXenes

Abstract

Electrocatalysis represents a promising method to generate renewable fuels and chemical feedstock from the carbon dioxide reduction reaction (CO 2 RR). However, traditional electrocatalysts based on transition metals are not efficient enough because of the high overpotential and slow turnover. MXenes, a family of two-dimensional metal carbides and nitrides, have been predicted to be effective in catalyzing CO 2 RR, but a systematic investigation into their catalytic performance is lacking, especially on hydroxyl (−OH)-terminated MXenes relevant in aqueous reaction conditions. In this work, we utilized first-principles simulations to systematically screen and explore the properties of MXenes in catalyzing CO 2 RR to CH 4 from both aspects of thermodynamics and kinetics. Sc 2 C(OH) 2 was found to be the most promising catalyst with the least negative limiting potential of −0.53 V vs RHE. This was achieved through an alternative reaction pathway, where the adsorbed species are stabilized by capturing H atoms from the MXene's OH termination group. New scaling relations, based on the shared H interaction between intermediates and MXenes, were established. Bader charge analyses reveal that catalysts with less electron migration in the *(H)COOH → *CO elementary step exhibit better CO 2 RR performance. This study provides new insights regarding the effect of surface functionalization on the catalytic performance of MXenes to guide future materials design.

Defect‐Enhanced CO2 Reduction Catalytic Performance in O‐Terminated MXenes

“…Therefore, with variations in either M, X or T x components, different interactions with CO 2 RR intermediates can be expected. Calculations on (perfect) MXenes have shown atypical intermediates for CO 2 RR to CH 4 , involving both −H‐ and −C‐coordinated intermediates [6b–d] . However, we note that systematic studies on more realistic, defective MXenes structures for CO 2 RR are absent.…”

Recent Progress in MXene‐Based Materials: Potential High‐Performance Electrocatalysts

“…The O termination groups on MXenes help to stabilize reaction intermediates through H coordination, resulting in marked departure from *CO binding strength as the main CO 2 RR activity descriptor observed on transition metal catalysts. [119] Chen et al [120] utilized the first-principles approach to systematically explore CO 2 RR properties on 17 different MXenes with OH termination groups from both aspects of thermodynamics and kinetics, and found that Sc 2 C(OH) 2 and Y 2 C(OH) 2 the most promising catalysts with limiting potential of −0.53 and −0.61 V, respectively, which was obviously less negative than Cu metal. At the same time, the competing HER was disfavored due to strong H binding.…”

Tuning 2D MXenes by Surface Controlling and Interlayer Engineering: Methods, Properties, and Synchrotron Radiation Characterizations

“…Reproduced with permission. [ 131 ] Copyright 2019, American Chemical Society. c) DFT study of electrochemical nitrogen reduction based on functionalized MXenes, i) schematic illustration of the nitrogen reduction process on the surface of MXenes; ii) calculated pourbaix diagrams for Mo 2 C with different functional groups, the relative stability at an applied voltage is referenced to the free energy of the bare Mo 2 C MXene; iii) calculated free energy diagrams for NRR mechanism on Mo 2 C MXene with different terminations.…”