Chen Hetian; Handoko Albertus D.; Xiao Jiewen; Feng Xiang; Fan Yanchen; Wang Tianshuai; Legut Dominik; Seh Zhi Wei; Zhang Qianfan. Catalytic Effect on CO2 Electroreduction by Hydroxyl-Terminated Two-Dimensional MXenes. ACS Applied Materials & Interfaces. 2019, vol. 11, issue 40, s. 36571-36579. ISSN 1944-8244, eISSN 1944-8252, DOI: https://doi.org/10.1021/acsami.9b09941.
Electrocatalysis represents a promising method to generate renewable fuels and chemical feedstock from the carbon dioxide reduction reaction (CO2RR). 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 efficient in catalyzing CO2RR, but a systematic investigation into their catalytic performance is lacking, especially on hydroxyl (–OH) terminated MXenes relevant in aqueous reaction conditions. The existence of hydroxyl makes the pathway much more complex because the H atom in hydroxyl group will participate in the formation of intermediates.
In this work, we utilize first-principles calculations to systematically screen and explore the chemical properties of MXenes in catalyzing CO2RR to CH4, from both aspects of thermodynamics and kinetics, showing how the hydroxyl affects the reaction. Sc2C(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 is stabilized by capturing H atom 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 CO2RR performance. This study provides new insights regarding the effect of surface functionalization on the catalytic performance of MXenes to guide future materials design.