Rational Design of Copper Alloy Catalysts for Electrochemical CO2 Reduction

Abstract

Electrochemical conversion of CO2 is a potentially exciting route towards production of sustainable drop-in fuels and chemicals using renewable electricity. A key obstacle in the commercial scale-up and deployment of CO2 utilization and conversion is the lack of active and selective catalysts. Across all monometallic candidates, Cu exhibits distinctive ability to electrochemically reduce CO2 to several products including methane and ethylene, albeit its multifunctional nature makes selectivity control challenging [1]. Alloying offers a means to break scaling relationships and uniquely manipulate the reactivity and selectivity in ways that would be hard to achieve using monometallic compositions alone. Here, we employ a coupled quantum mechanics/molecular mechanics (QM/MM) scheme [2] to screen various copper alloys for their reactivity and selectivity towards key rate-limiting and selectivity-determining steps in CO2 conversion. The activity-selectivity screening is carried out under reducing conditions to thoroughly probe the influence of the electrolytic ions under the applied potential on the alloy stability and reactivity. The results of these studies show how alloying in conjunction with electrolyte tuning can non-intuitively alter the surface electronic and catalytic properties of the catalyst leading to changes in activity-selectivity towards CO2 conversion. This serves to provide a rationale for improved composition and environment driven design and screening, and allows the use of chemical computation using nuanced, dynamical models of the electrochemical double layer[i].[1] Y. Hori, in Handbook of Fuel Cells: Fundamentals, Technology and Application (VHC Wiley, Chichester, 2003), Vol. 2, 720-733.[2] 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. [i] This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.