Electrochemical reduction of CO2 to utilize and convert CO2 gas into fuels is a potential solution to answer the environmental issue caused by the high CO2 atmospheric concentration. Nanostructured metallic catalysts, which possess distinct structural properties over bulk catalysts, have been developed to have enhanced performances. Lately, we have developed nanostructured Au and Ag to have enhanced performances in CO2 reduction reaction (CO2RR) towards CO production. Zn is another promising metallic catalyst for electroreduction of CO2 that is a cost-effective alternative to noble metals, but relatively less studies are performed. Herein, we report that porous nanostructured Zn based catalysts reduced from its oxide/hydroxide can enhance electrochemical activity of CO2 to CO conversion with high efficiency and selectivity, and the significance of the initial activation step in high CO2RR activity. Particularly, electrolyte environment during reduction activation step plays a role to enhance the catalyst selectivity and decrease carbon impurity deposit. The more oxidized zinc proportion relates to the enhancement of selective CO production and is obtained when bubbling CO2 gas in reduction activation step. Furthermore, the extensive effects of halides, which can enhance electrochemical activity of CO2 to CO conversion with high efficiency and selectivity, were investigated on porous nanostructured Zn-based catalysts in different halide electrolytes from KF to KI. Our results revealed that the effect of adsorbed halides is critical to the stabilization of the *COOH intermediate resulted from facilitating the charge donation from halide ions to CO2 coupled with the proportion of oxidized zinc components and stable oxygen species, thus, determine the activity for CO2 to CO of electrocatalysts. From a thermodynamic perspective, however, CO2 electroreduction towards CO product in bicarbonate electrolyte encounters the unwanted competition of hydrogen evolution reaction (HER) caused by their similarities of required overpotential to drive products formation. Taking note of the above observations, we have developed a new nanocomposite electrocatalyst from zinc oxide and one kind of popular carbon material to efficiently suppress the HER achieving superior Faradaic efficiency for high rate production of CO gas from CO2. We believe that our studies on Zn-based electrocatalysts can provide a platform for applications for CO2RR in industry.

Achieving highly effective and selective electroreduction of CO2-to-CO on porous nanostructured ZnO derivatives

2019 Fall National Meeting

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