Atomic scale modelling of transition metal dichalcogenide electrocatalysts for the electrocatalytic CO2 reduction reaction

Pernille Pedersen

Research output: Book/ReportPh.D. thesis

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Abstract

Electrocatalytic CO2 reduction (CO2RR) utilizing renewable energy and captured CO2 from hard-to-abate sectors offers a promising solution for generating net zero fuels and chemicals while serving as an energy storage technology. Existing catalysts suffer from low efficiency and selectivity. One of the main challenges to be overcome in the process of designing new and improved catalysts is the competition with the Hydorgen Evolution Reaction (HER). Among the transition metals copper (Cu) stands out due to its unique ability to reduce CO2 to highly reduced products, thanks to its intermediate adsorption strength of both CO and H.

The Transition Metal Dichalcogenides (TMDCs) are a group of promising candidate materials. In this thesis the catalytic activity and stability of 2H TMDC edges has been investigated. It is found that the favored edge termination is very dependent on the potential and pH under relevant operating conditions. Also the stability regions of different terminations are significantly different for different TMDCs. The study shows interesting trends in the adsorption energies of H and CO, crucial for the CO2RR selectivity. Larger anion size is found to lead to a shift toward stronger CO adsorption and weaker H adsorption, indicating the possibility of producing “beyond CO” products.

Furthermore, the potential dependence of CO2RR and HER mechanisms on MoTe2 using Grand Canonical DFT (GC-DFT) is investigated. It is found, that while a purely thermodynamic analysis suggests that the HER is favored, including also kinetics, which is possible only because of the explicit inclusion of potential, CO2RR is in fact favored, in agreement with previous experimental studies. This highlights the necessity of going beyond the Computational Hydrogen Electrode (CHE) model to fully comprehend electrocatalytic activity. Additionally, different intermediate steps exhibit varying potential behaviors, influencing the the balance between HER and CO2RR as well as CO desorption and further reduction.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages128
Publication statusPublished - 2023

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