Product Distribution Control Guided by a Microkinetic Analysis for CO Reduction at High-Flux Electrocatalysis Using Gas-Diffusion Cu Electrodes

Abstract

In addition to the identity of the electrocatalyst materials, the catalytic performance is strongly influenced by the local steady-state environment perturbed by reaction conditions (pressure and temperature) and the operating current density. Strategies developed by the experiments at low current densities often cannot be simply extrapolated to practical high electrocatalytic performance achieving over 1 A cm-2. In this study, the detailed microkinetic analysis of high-flux electroreduction of CO was carefully examined over high-surface-area Cu-based electrocatalysts in the form of gas-diffusion electrodes (GDEs). The study includes Tafel analysis, kinetic isotope effects, and temperature and pressure dependence measurements to establish rate expressions based on elementary steps and interpret the reaction pathways. Further digesting the kinetic data as a function of CO partial pressure (PCO) and reaction temperature disclosed higher PCO favored n-propanol (n-PrOH) and acetate at the expense of C2H4 and C2H5OH, pinning down the optimal operating conditions to maximize the performance of a specific product at a given overpotential. These findings reinforce the importance of “beyond catalyst” phenomena in modern electrocatalysis.