Understanding the Temperature Effect on Carbon-Carbon Coupling during CO₂ and CO Electroreduction in Zero-Gap Electrolyzers

Abstract

Cu-catalyzed electrochemical CO ₂ reduction reaction (CO ₂RR) and CO reduction reaction (CORR) are of great interest due to their potential to produce carbon-neutral and value-added multicarbon (C ₂₊) chemicals. In practice, CO ₂RR and CORR are typically operated at industrially relevant current densities, making the process exothermal. Although the increased operation temperature is known to affect the performance of CO ₂RR and CORR, the relationship between temperatures and kinetic parameters was not clearly elaborated, particularly in zero-gap reactors. In this study, we detail the effect of the temperature on Cu-catalyzed CO ₂RR and CORR. Our electrochemical and operando spectroscopic studies show that high temperatures increase the activity of CO ₂RR to CO and CORR to C ₂H ₄ by enhancing the mass transfer of CO ₂ and CO. As the rates of these two processes are highly influenced by reactant diffusion, elevating the operating temperature results in high local CO ₂ and CO availability to accelerate product formation. Consequently, the *CO coverage in both cases increases at higher temperatures. However, under CO ₂RR conditions, *CO desorption is more favorable than carbon-carbon (C—C) coupling thermodynamically at high temperatures, causing the reduction in the Faradaic efficiency (FE) of C ₂H ₄. In CORR, the high-temperature-augmented CO diffusion overcomes the unfavorable adsorption thermodynamics, increasing the probability of C—C coupling.

Keywords

Zero-gap electrolyzers / CO ₂ and CO reduction / Temperature effect / Selectivity / C—C coupling / Adsorption

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2024 SIOC, CAS, Shanghai, & WILEY-VCH GmbH