Redox Flow Batteries using Carbon Dioxide; from electrocatalysis to cell engineering

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Mitigation of carbon dioxide emissions, clean energy generation and its storage are widely recognized as among the most stringent technological challenges of the twenty first century. A major drawback for large scale adoption of many clean energy technologies is the intermittent nature of the energy generation cycle (peak vs. off-peak) requiring efficient energy storage devices. Electrochemical technologies are intensely investigated for both clean energy generation and storage (e.g., various batteries, fuel cells and supercapacitors) and CO2 conversion to useful chemicals (by electro-reduction). The present discovery research program proposes to unite for the first time these two previously separate fields in a novel redox flow battery technology invented by the applicant based on the CO2 / formic acid (or formate anion) redox couple at the negative electrode. During battery charging using renewable energy source, CO2 is reduced to formic acid (or formate anion, depending on pH), which acts as energy storage medium. At the positive electrode, a redox couple commonly used in flow batteries (e.g., bromide – bromine) is employed. In the battery discharge cycle electric power is produced by reversing the reactions (e.g., at the negative electrode formic acid is oxidized back to CO2). The theoretical specific energy density of the carbon dioxide/formic acid – bromide/bromine redox flow battery is 547 Wh per kg of reactants at 298 K. This approach, if successful, could provide industrial CO2 emitters (e.g., coal fired power plants, cement and steel manufacturing plants etc.) with a carbon-neutral energy generation and storage technology, while reducing the CO2 emitted to the atmosphere. In other words, it is a novel approach for conversion of CO2 waste to energy.***The battery round-trip efficiency, defined as the electric energy generated during discharge divided by the electric energy consumed for charging, is a very important figure of merit and ultimately, together with cost and scaling, determines the practical viability of this technology. The present research program is focused on addressing some of the major fundamental electrocatalytic and electrochemical engineering challenges. These are: a) research and development of bifunctional (reversible) CO2 reduction – formic acid oxidation electrocatalysts, b) evaluation and investigation of suitable positive electrode redox couples, and c) CO2 flow battery engineering. The novelty of the proposed research program requires truly innovative contributions and discoveries that are ideal for training a new generation of professionals (2 PhD, 1 MASc, and 5 undergraduate students) in the areas of applied electrocatalysis, surface science and electrochemical engineering for the benefit of the Canadian industrial and academic sectors focused on renewable energy and carbon emission mitigation.**