System Design Rules for Intensified CO₂ Electroreduction

Addition of about 14.7 Gigatons per year of net CO2 to the atmosphere has resulted in the atmospheric CO2 concentrations to increase from 316 ppm to 413 ppm over the past 60 years.1, 2 Excess CO2 can be remediated by capturing the excess CO2 emissions and subsequently utilizing them to make value-added products.3 CO2 electroreduction (ECR) is a potential method for converting a fraction of the excess CO2 emissions into carbon-based value-added chemicals such as carbon monoxide, hydrocarbons, and oxygenates.4 Academic and industrial research over the past decade has resulted in active and selective catalysts as well as energy-efficient cell configurations for ECR, however, significant improvements are still needed in electrochemical performance for ECR to become economically feasible at scale.5-7 The first part of this talk will focus on the role of electrolyte composition in the mechanism of ECR to CO on Ag nanoparticles. Specifically, the effects of pH, electrolyte identity, electrolyte concentration, and applied potential on the rate determining step will be discussed. A combination of measurements based on onset potentials, Tafel slopes, and electrochemical impedance spectroscopy can explain the promotional behavior of cations and the overpotential reduction for cell operation under high pH.8 The second part of this talk will cover a systematic process optimization of ECR to CO on Ag nanoparticles in a gas diffusion electrode based flow electrolyzer resulting in state-of-the-art electrochemical performance: a CO partial current density exceeding 850 mA/cm2 with a CO Faradaic efficiency of 98% at a cell potential of -3 V corresponding to a full cell energy efficiency exceeding 40% for a conversion per pass of CO2 exceeding 35%.8 Finally, this talk will also discuss how establishing quantitative/qualitative functional property relationships between system parameters (e.g.: pH, electrolyte flow rate) and system performance (e.g.: cathode overpotentials, CO partial current density) can help in rational system design for ECR to CO on Ag nanoparticles.8 References IPCC, Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2013. https://www.esrl.noaa.gov/gmd/ccgg/trends/, (accessed 17 December 2020). S. Pacala and R. Socolow, Science, 2004, 305, 968. O. S. Bushuyev, P. De Luna, C. T. Dinh, L. Tao, G. Saur, J. van de Lagemaat, S. O. Kelley and E. H. Sargent, Joule, 2018, 2, 825-832. B. Endrődi, G. Bencsik, F. Darvas, R. Jones, K. Rajeshwar and C. Janáky, Progress in Energy and Combustion Science, 2017, 62, 133-154. S. Verma, B. Kim, H.-R. M. Jhong, S. Ma and P. J. A. Kenis, Chemsuschem, 2016, 9, 1972-1979. M. Jouny, W. Luc and F. Jiao, Industrial & Engineering Chemistry Research, 2018, 57, 2165-2177. S. S. Bhargava, F. Proietto, D. Azmoodeh, E. R. Cofell, D. A. Henckel, S. Verma, C. J. Brooks, A. A. Gewirth and P. J. A. Kenis, ChemElectroChem, 2020, 7, 2001-2011.