Efficient CO2 utilization in acid electrolytes via Ni single atom catalysts with nafion membrane-based flow cells

Abstract

In a highly developed society, an increase in the concentration of carbon dioxide is inevitable, and climate change represented by global warming becomes a considerable problem. In order to respond to this, many works are being made to capture and utilize carbon dioxide around the world, and the electrochemical carbon dioxide reduction reaction is a representative. In the carbon dioxide reduction reaction, the reduction potential of carbon dioxide is similar to that of hydrogen evolution, thus hydrogen evolution reaction acts as a competitive reaction. In order to suppress this competitive reaction, researches were mainly conducted under alkaline conditions. In these conditions, high Faraday efficiency can be obtained, but there is a limit in terms of efficiency because carbon dioxide is converted into undesired carbonates. Since the carbon dioxide reduction reaction is known to be unaffected by the concentration of hydrogen ions, if there is a catalyst that can reduce carbon dioxide better than the competitive reaction, the efficiency limit can be overcome even under acidic conditions. In this thesis, we will show that with Nafion membrane and nickel single atom catalysts show superior carbon dioxide reduction performance compared to commercial silver catalysts under acidic conditions. In addition, it will be shown that by controlling the flow rate of carbon dioxide supply and a current density to obtain a high single-pass conversion, it is necessary to develop a superior catalyst as well as system improvement to achieve a commercial level of carbon dioxide reduction.