The development of high performance catalysts for the production of fuels and chemical in electrochemical reactors call for a profound understanding of the processes occurring at multiple scales and emphasizes the importance of broadening catalyst design principles beyond the transition state theory to include fundamentals of mass and charge transport. The selective production of C2+ alcohols on cooper electrodes requires that multiple thermo-chemical and electro-chemical steps occur at the electrode-electrolyte interface at rates faster than those for the competing hydrogen and hydrocarbon evolution reactions. At the same time, the rates of most of these reactions are not only dependent on the intrinsic activity of copper, but are highly affected by the local environments that determine the rate of regeneration of reaction intermediates, the availability of proton sources for proton-electron coupled steps and the extend of the thermodynamic driving force for the formation of each of the multiple products. In this talk, we present a mathematical model based on the Poisson-Nernst-Planck equation that describes transport phenomena within an electrochemical cell and that can be used to rationalize experimental observations towards a better understanding of the nature of electrode/electrolyte interfaces during CO2 reduction to C2+ alcohols. Mathematical modeling is shown as a useful tool to decouple intrinsic electrode kinetics from transport-related effects. Charge transfer coefficients and pre-exponential factors are extracted from experimental data to describe the intrinsic activities of copper and other transition metal electrodes during the electrochemical reduction of CO2 to CO, alcohols and hydrocarbons. We demonstrate the rational application of this mathematical model in the design of more active and selective electrocatalyst for C2+ alcohol production by introducing cooperative catalysis schemes where gold nanoparticles generate high local concentrations of carbon monoxide intermediates on neighboring copper sites that catalyze the production of C2+ alcohols at higher rates than without gold. Electrode nanostructuring is also leveraged to create cooperative interactions withing electrode pores to increase the rate of C2+ alcohols formation. Finally, the extent to which these mathematical models are valid for the description of the kinetics for mass transport and charge transfer in modular electrochemical reactors is discussed.

Combined experimental and multi-scale modeling approach to the development of tandem electrocatalysts with improved CO2 reduction activity towards C2+ alcohols

ACS Fall 2020 Virtual Meeting

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