Converting waste CO2 into fine chemicals and/or fuels is an exciting prospect for green-house gas mitigation. Current CO2 conversion approaches include photo-, electro- and thermo-catalytic processes. Each have their respective benefits, but electrocatalytic CO2 conversion is a leading candidate because it operates at ambient conditions with extremely high reaction rates, product selectivity and faradaic efficiency, and it requires small energy input (several volts). Carbon balance is a major consideration for any CO2 conversion technology because the majority of the United States' electricity is derived from burning fossil fuels. This necessarily shifts most CO2 conversion technologies into the carbon positive regime, and CO2 produced from fossil-fuel derived electricity will likely exceed that consumed by the conversion process. This limitation is an important challenge that must addressed before CO2 conversion technologies can be implemented on an industrial scale. Here, we describe a “carbon-negative” (more CO2 consumed than produced) electrochemical CO2 conversion system that operates on inexpensive (ca. $10-20 USD), consumer-grade photovoltaic cells and solar-rechargeable batteries. We show stable CO2 → CO conversion activity with turnover numbers (TON: mol CO2/mol catalyst) surpassing 5x106, rates exceeding 800 L CO2 /gram catalytic metal/hour, and faradaic efficiencies and product selectivities around 90%. These performance metrics correspond to 1-2 kg CO2 converted per gram of catalytic metal every hour. We can also tune product selectivity to favor CO or H2 production by varying the catalyst loading and/or operating voltage. We show stable operation for 12 hours with photovoltaic cells to represent daylight operation, and 24 hours with a solar-rechargeable battery to mimic low-light or night-time hours. This study provides proof-of-principle example that renewable-powered electrocatalysis is a viable strategy for CO2 conversion applications.

Carbon negative, renewable energy compatible electrochemical process for converting CO2 and water into CO and H2

249th National Meeting (2015)

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Carbon negative, renewable energy compatible electrochemical process for converting CO2 and water into CO and H2<br />

Carbon negative, renewable energy compatible electrochemical process for converting CO₂ and water into CO and H₂<br />