Over the last 5 decades, the global atmospheric CO2 concentration has increased to 400 ppm. This high, and still rising CO2 level has been connected with global warming and increasing occurrences of erratic weather events. A variety of strategies needs to be pursued to curb the increase in atmospheric CO2. A potential strategy that can be employed to overcome this challenge is the electrochemical reduction of CO2 into useful feedstock chemicals or fuels such as formic acid, carbon monoxide, hydrocarbons, and alcohols. This process can be driven by the vast amounts of intermittent excess renewable power that is becoming available. Among the chemicals that can be produced, ethylene and ethanol (C2 products) are preferred over other products because they are either important industrial raw materials or high energy-density fuels. Although the electrochemical reduction of CO2 to value-added products has promise to help curb global CO2 levels, the high overpotential of this reaction and low activity of the catalysts being used still hamper the feasibility of this process. Cu is the only metal that catalyzes CO2 to C2 products at a considerable high Faradaic efficiency (FE). However, the overpotentials for C2 chemical production using Cu catalysts are high (0.7 to 1 V), resulting in the low overall energetic efficiency. Also, the production rates reported to date are quite low (current densities &lt; 35 mA cm-2 under ambient conditions). Here, we report the efficient electrochemical reduction of CO2 to C2 products at low overpotentials and high production rates in an alkaline flow cell, using active Cu nanoparticles (CuNPs) deposited on gas diffusion electrodes (GDEs) as the cathode catalysts. The current density for C2 products achieved by CuNP in this study reaches 200 mA cm-2, which is about one order-of-magnitude higher than the data reported in most of the prior work. The higher performance in this study is due to the successful use of GDEs to overcome the limitation of the low solubility of CO2, as well as the application of active and stable Cu nanoparticle with high surface area in an alkaline medium.

Efficient electrochemical conversion of CO2 to ethylene and ethanol in an alkaline electrolyzer

251st National Meeting (2016)

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