Grand Canonical DFT Investigation of the CO2RR and HER Reaction Mechanisms on MoTe2 Edges

Abstract

MoTe2 has been experimentally and theoretically identified as a promising cathode candidate for electrocatalytic CO2 reduction (CO2RR). A full understanding of its reactivity requires special consideration of the reaction kinetics, but this is challenging due to the varying electrode potential in the canonical density functional theory (DFT), which calls for grand canonical, constant potential methods. Here, the full reaction pathways for the CO2RR to CO and the competing hydrogen evolution reaction (HER) are investigated on a MoTe2 edge in an alkaline medium using a grand canonical ensemble DFT approach with a hybrid solvent model to understand the explicit effect of the applied potential. Our results show that the barrier of the first CO2RR step, the CO2 adsorption, is lower than the first HER step, the Volmer step, which implies that the CO2RR is favored. We also find that at more negative potentials, the first CO2RR steps become more favorable, whereas CO desorption becomes less favorable, indicating that further CO reduction is expected instead of CO desorption. However, the potential of the Volmer step depends more strongly on the potential than CO2 adsorption, making HER more favorable at more negative potentials. Overall, our study identified edge-rich MoTe2 nanoribbons as possible catalysts for alkaline CO2RR.