Probing the Electrocatalytic Activity of Chromium Gallium Oxide in the Reduction of CO2 Through Morphological Variations

Abstract

Developing technologies to reduce atmospheric carbon dioxide emissions, and thus mitigate global climate change, has become an increasingly large field of scientific research over the past few decades, due to the implications of our current energy technology. Recycling CO2 through electrochemical methods is one of many approaches looking to contribute to this project. The employment of electrocatalysts can utilize intermittent renewable power to reduce CO2 to useful fuels and feedstock chemicals. This thesis reports continued research on a previously discovered 3:1 Cr:Ga oxide electrocatalyst through modifications to its morphology. By synthesizing targeted morphologies which differ from the original, insights about the active properties of the material can be made, and future projects can be better aimed. Ten morphologies were synthesized, imaged, and electrocatalytically tested to compare to the native catalyst. Through this experimentation, it was found that ease of mass transport away from the environment created by the Cr-Ga oxide at the glassy carbon surface was key in product determination and efficiency. Morphologies which trapped the CO2 closer to the electrode through physical Cr-Ga oxide boundaries and hypothesized preferential binding sites were more likely to have higher Faradaic efficiency for more reduced and carbon-coupled products. These results suggested that the role of the Cr-Ga oxide was to increase CO2 density near the electrode and therefore kinetically catalyze its electroreduction. The morphologies which increased the Faradaic efficiency of larger and more reduced products were those which were synthesized directly on the glassy carbon electrode, as opposed to an independently synthesized and then adhered powder. Electrode coverage by the oxide also proved to be correlated positively with all organic product efficiency, in competition with hydrogen evolution. These discoveries can be used to guide the development of improved versions of this material in the future.