Double-layer effect on the kinetics of CO2 electroreduction at cathodes bearing Ag, Cu, and Ag/Cu nano-arrays electrodeposited by potentiostatic double-pulse.

Graphical abstract Highlights • In-doped SnO 2 cathodes bearing Ag, Cu and bimetal Ag/Cu nanoparticulate arrays were prepared by potentiostatic double-pulse technique. • These cathode systems were employed for studying the multi-step charge-transfer kinetics of CO 2 electrochemical reduction in propylene carbonate solutions. • Current exchange density of CO 2 electrochemical reduction at rate-determining step depends in large part on the values achieved by the outer-Helmholtz plane potential for the three cathode systems that we explored. • Individual electrocatalytic properties of Ag and Cu were successfully coupled when deposited in a bimetallic array to intentionally tune the CO 2 electrochemical reduction rate in propylene carbonate. Abstract In-doped SnO 2 (ITO) cathodes bearing Ag, Cu and bimetallic Ag/Cu nanoparticulate arrays (cathode systems ITO//Ag, ITO//Cu and ITO//Ag/Cu, respectively) were prepared by a potentiostatic double-pulse technique and employed for studying the multi-step charge-transfer kinetics of CO 2 electrochemical reduction (CO 2 ER) in propylene carbonate solution. Our results demonstrated, on one hand, that the current exchange density of the rate-determining step (rds) for the CO 2 electrochemical reduction (i o,rds) depends, predominantly, on the values achieved by the outer-Helmholtz plane (OHP) potential (Δψ OHP, rds) on the three cathode systems here explored. Furthermore, these results showed that a large Δψ OHP, rds (−647 mV) promoted a large i o,rds (1.09 × 10⁻² A⋅ cm⁻²) for CO 2 reduction at the cathode system ITO//Cu, whereas a small Δψ OHP, rds (−168 mV) produced a small i o,rds (2.05 × 10⁻⁴ A⋅ cm⁻²) for CO 2 reduction at the cathode system ITO//Ag. In contrast, intermediate values of Δψ OHP, rds and i o,rds (−333 mV, 1.09 × 10⁻³ A⋅ cm⁻²) were found for CO 2 reduction on the cathode system ITO//Ag/Cu, demonstrating that the individual electrocatalytic properties of Ag and Cu can be coupled in a bimetallic array to intentionally tune the CO 2 ER rate in nonaqueous solvents having low proton availability. [ABSTRACT FROM AUTHOR]