Intensifying the CO2 Electrolysis Process

Abstract

Every year we emit approximately 26 billion tons of CO2 to the atmosphere.1 As a result, the atmospheric CO2 concentration has increased from 316 to 408 ppm (NOAA, Mauna Loa HI) over the past 50 years. Global temperature anomalies have increased by 1°C leading to adverse environmental impact. The atmospheric CO2 concentration needs to be reduced in order to curb such effects. Electrochemical conversion of CO2 into value added chemicals such as methanol, formic acid, and carbon monoxide is a promising method for reducing the excess atmospheric CO2 content.2-5 If the end product obtained from the process is CO, the system could be coupled to a Fischer Tropsch (FT) reactor to form liquid fuels.6 Many research efforts in academia and industry seek to identify and optimize suitable catalysts, electrodes, electrolytes, and associated operation conditions that allow for the energy efficient and selective electrolysis of CO2 into one of the aforementioned value-added intermediates.6 By using a gas-diffusion electrode (GDE) based flow electrolyzer, CO2 can be fed as a gas, thereby circumventing any solubility and mass transfer issues, resulting in high current densities (>400 mA cm-2).7-8 Despite progress in catalyst activity and selectivity, as well as in electrode and electrolyzer performance, still significant further improvements are needed to reach techno-economic feasibility at scale.9 This presentation will cover multiple directions that can be explored (for an alkaline GDE-based flow electrolyzer) to achieve the needed improvement in performance: The first part of this presentation will cover process optimization where we systematically vary various process parameters like cathode catalyst loading, electrolyte flow rate, and electrolyte concentration to operate at peak performance. In the second part, we will cover how electrolyte composition can be tailored to achieve higher current densities and better Faradaic efficiencies by using high pH and using large alkali metal cations such as Cs+. The third part demonstrates the use of a Ni & Fe based bimetallic anode catalyst which gives a 200 mV reduction in overpotential compared to the typically used IrO2 anode catalyst. And lastly, in the fourth part, we present some results regarding further process intensification where we studied the effect of operating temperature. References J. Oerlemans, Science, 2005, 308, 675-677K. W. Frese, S. Leach, Journal of the Electrochemical Society, 1985, 132, 259-260Y. Hori, H. Wakebe, T. Tsukamoto, O. Koga, Electrochimica Acta, 1994, 39, 1833-1839Y. Hori, K. Kikuchi, S. Suzuki, Chemistry Letters, 1985, 11, 1695-1698B. A. Rosen, A. Salehi-Khojin, M.R. Thorson, W. Zhu, D.T. Whipple, P.J.A. Kenis, R.I. Masel, Science, 2011, 334, 643-644B. Endrodi, G. Bencsik, F. Darvas, R. Jones, K. Rajeshwar, C. Janaky, Progress in Energy and Combustion Science, 2017, 62, 133-154D. T. Whipple, E.C. Finke, P.J.A. Kenis, Electrochemical and Solid-State Letters, 2010, 13, B109-B111S. Verma, X. Lu, S. Ma, R. I. Masel, P. J. A. Kenis, Physical Chemistry Chemical Physics, 2016, 18, 7075-7084S. Verma, B. Kim, H. R. M. Jhong, S. Ma, P. J. A. Kenis, ChemSusChem, 2016, 9, 1972-1979