Tuning the Sensitivity of CO2 Electroreduction on Copper Surfaces Via Electrolyte Engineering

Abstract

With growing increase in energy demand and chemical production, electrochemical reduction (ER) of CO2 can potentially pave the route for generation of sustainable drop-in fuels using renewable wind and solar energy sources. Cu has been identified as a promising electrocatalyst for CO2 conversion to methane and ethylene, albeit the rates of the electrocatalytic reactions are strongly influenced by the reaction environment and the operating conditions [1,2]. Electrolytic ions are known to impact the rates of electrocatalytic reactions, though a molecular understanding of such impact is not comprehensively understood. Here, we employ a coupled quantum mechanics/molecular mechanics (QM/MM) scheme [3] to investigate the role played by the electrolytic ions under applied potential on the activity-selectivity relationships for CO2 ER. By varying the concentration and identity of electrolytic salts, we investigate their effect on the reaction energetics and binding strength of reaction intermediates in the CO2 ER pathway. Using a high throughput combinatorial approach that spans a wide range of electrolytes, we attempt to create design principles for electrolyte-based tuning of CO2 ER selectivity and compare with experimentally measured CO2 ER selectivities. The results of these studies provide a rationale for improved environment driven design and screening, and allow computation of reaction energetics using nuanced, dynamical models of the electrochemical double layer.* [1] Y. Hori, in Handbook of Fuel Cells: Fundamentals, Technology and Application (VHC Wiley, Chichester, 2003), Vol. 2, 720-733. [2] A. Murata & Y. Hori, Product selectivity affected by cationic species in electrochemical reduction of CO2 and CO at a Cu electrode. Bulletin of the Chemical Society of Japan (1991), 64(1), 123-127. [3] J. Haruyama, T. Ikeshoji and M. Otani, Electrode potential from density functional theory calculations combined with implicit solvation theory. Physical Review Materials (2018), 2(9), p.095801. *This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.