Computational Identification of Transition-Metal Dichalcogenides for Electrochemical CO₂ Reduction to Highly Reduced Species Beyond CO and HCOOH

Abstract

Practical CO2 reduction (CO2R) catalysts are desirable to have high selectivity for highly reduced products at small overpotentials and minimal activity for the hydrogen evolution reaction (HER). Herein, to find such catalysts, we investigate the CO2R activities of anion vacancies of two-dimensional (2D) transition-metal dichalcogenides (TMDs) by first-principles calculations. For 38 TMDs found in experiments, we calculate free energies of intermediates along the pathways to C1 products. In most TMDs, the steric hindrance of anion vacancies leads to the selective reduction of CO2 to HCHO. Among them, we suggest ReS2 and ReSe2 as promising candidates having a low onset potential for CO2R and high selectivity vs the HER. In addition, they allow further reduction of HCHO to highly reduced species. Detailed mechanism analysis shows that free energies of *OCHO and *H (* denotes adsorbates) can be descriptors for efficient evaluation of CO2R activities. Given the importance of the geometrical constraints of vacancies for the CO2R mechanism, our results will help identify potential CO2R catalysts with vacancies that are electrochemically active.