Electrochemical and in situ FTIR studies of carbon dioxide reduction at cobalt-based and cobalt-copper nanostructured catalysts

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University of Guelph

Abstract

The advancement of cost-effective nanostructured catalysts for the electrochemical reduction of CO2 to valuable chemicals is of great interest, but progress is hindered by the lack of fundamental understanding of reduction reaction mechanisms. That can impede the fine-tuning of the elemental and morphological properties of surfaces towards more efficient electrochemical catalysts. In this thesis, self-supported cobalt-oxide and cobalt-copper nanocatalysts were synthesized and systemically studied for the electrochemical CO2 reduction reaction (CO2RR). The effects of surface modification techniques such as acid-etching and thermal annealing on the catalytic activity and product selectivity were studied. In the first project, Co nanodendrites were directly grown on the electrode surface and were found to exhibit superb catalytic activity with a small onset potential (-0.2 V vs RHE). In situ electrochemical attenuated total reflection Fourier transform infrared spectroscopy (ATR - FTIR) was employed to elucidate the reduction reaction mechanism catalyzed by the Co nanodendrites. This study revealed that the formation of formate at the surface of Co nanodendritic proceeded through the formation of a carbon-bound adsorbed intermediate. In the second project, self-supported cobalt/copper nanostructured catalysts were fabricated using thermal, acid-etching, and galvanic replacement techniques. The influences of the elemental composition and acid-etching on the morphology of the catalyst and its efficiency towards CO2RR were studied. The optimized Co/Cu catalysts showed high catalytic activity with 93% current efficiency at -0.4 V vs. RHE, and low onset potential at -0.2 V vs. RHE. Gas and liquid product analysis revealed that formate and carbon monoxide were produced with maximum Faradaic efficiencies of 32 % and 74 %, respectively. It was observed that lower reductive potential was favourable towards formate production while higher reductive potential was more favourable towards CO production. In the third project, self-supported copper/cobalt nanostructured catalysts were fabricated using electrodeposition, thermal, and acid-etching techniques. Changes in the performance and product selectivity due to the order of deposition of cobalt and copper on the electrode surface were investigated. The optimized Cu/Co catalysts showed high catalytic activity with 99% current efficiency at -0.4 V vs. RHE, and low onset potential at -0.4 V vs. RHE. The novel synthetic procedures reported in this thesis can lead to the design of promising electrocatalysts with high efficiencies for CO2 reduction into valuable products.

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Electrocatalysts, Electrochemical CO2 reduction reaction, Cobalt, Copper, Nanostructures, in situ electrochemical FTIR

Citation

Abner, S.; Chen, A. Design and Mechanistic Study of Advanced Cobalt-Based Nanostructured Catalysts for Electrochemical Carbon Dioxide Reduction. Appl. Catal. B: Environ. 2022, 301, 120761. https://doi.org/10.1016/j.apcatb.2021.120761.