Dynamic Boundary Layer Simulation of Pulsed CO₂ Electrolysis on a Copper Catalyst

Abstract

Pulsed electrolysis has been demonstrated to improve the faradaic efficiency (FE) to C 2+ products during the electrochemical reduction of CO 2 over a Cu catalyst, but the nature of this enhancement is poorly understood. Herein, we developed a timedependent continuum model of pulsed CO 2 electrolysis on Cu in 0.1 M CsHCO 3 that faithfully represents the experimentally observed effects of pulsed electrolysis. This work shows that pulsing results in dynamic changes in the pH and CO 2 concentration near the Cu surface, which lead to an enhanced C 2+ FE as a consequence of repeatedly accessing a transient state of heightened pH and CO 2 concentration at high cathodic overpotential. Using these insights, a variety of pulse shapes were explored to establish operating conditions that maximize the rate of C 2+ product formation and minimize the rates of H 2 and C 1 product formation.

Highly selective and productive reduction of carbon dioxide to multicarbon products via in situ CO management using segmented tandem electrodes

“…This rate order is consistent with the linear trends observed in Fig. 2e and is consistent with previous experimental studies of CO reduction (COR) 9,12,26,30,34 . However, recent studies of vapour-phase COR have demonstrated that appreciable θ *CO can be achieved in porous catalyst layers, causing the rate order with respect to CO concentration to decrease as the partial pressure increases, a behaviour captured by a Langmuir adsorption model (Supplementary Fig.…”

“…A two-dimensional (2D) continuum model of the cathodic chamber of the cell was developed to rationalize and guide the results and design, respectively. Multiple previous studies in aqueous electrolytes have shown that the generation of C 2+ products from CO follows an approximately first-order rate dependence on CO concentration at low CO partial pressures, for which the fraction of empty Cu sites is near unity 2,9,26,[34][35][36][37][38] . This rate order is consistent with the linear trends observed in Fig.…”

Dynamic Evolution of Active Sites in Electrocatalytic CO2 Reduction Reaction: Fundamental Understanding and Recent Progress

“…The higher local pH and CO accumulation were thus achieved, benefiting to C 2+ production and HER suppression. [43,190,191] The net effect of alternating cathodic potentials also helps accumulate CO 2 in electrode surface to enhance carbon compounds production over HER. [45] In addition to CO 2 RR activity and selectivity, pulsed electrolysis further shows its availability to improve the stability of gas diffusion electrode (GDE)-based CO 2 RR electrolyzer.…”

“…The higher local pH and CO accumulation were thus achieved, benefiting to C 2+ production and HER suppression. [ 43,190,191 ] The net effect of alternating cathodic potentials also helps accumulate CO 2 in electrode surface to enhance carbon compounds production over HER. [ 45 ]…”

The Role of Roughening to Enhance Selectivity to C2+ Products during CO2 Electroreduction on Copper

“…Despite decades of research efforts, Cu remains the only catalyst capable of producing significant amounts of C 2+ products, containing more than one carbon atom . In doing so, however, Cu also produces a medley of other products of varying economic value, presenting a challenge for industrial viability in the absence of a carbon tax or credit. , Several strategies for improving the Faradaic efficiency of Cu toward C 2+ products have emerged, including engineering of the electrode assembly − and electrolyte, − dynamic potential control, − and surface roughening. − In this contribution, we examine opportunities and intrinsic limitations in tuning catalytic selectivity of copper via surface structure engineering.…”