Understanding the Temperature Effect on Carbon-Carbon Coupling during CO_(2)and CO Electroreduction in Zero-Gap Electrolyzers

Comprehensive Summary Cu-catalyzed electrochemical CO_(2)reduction reaction(CO_(2)RR)and CO reduction reaction(CORR)are of great interest due to their potential to produce carbon-neutral and value-added multicarbon(C2+)chemicals.In practice,CO_(2)RR 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_(2)RR 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_(2)RR and CORR.Our electrochemical and operando spectroscopic studies show that high temperatures increase the activity of CO_(2)RR to CO and CORR to C2H4 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_(2)RR 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_(2)H_(4).In CORR,the high-temperature-augmented CO diffusion overcomes the unfavorable adsorption thermodynamics,increasing the probability of C—C coupling.