Electroanalytical Implications of an Interfacial Insulating Metal Oxide Layer: Impact of a Porous Cr₂O₃–Ga₂O₃ Layer on Electron Transfer and Heterogeneous Electrocatalysis

The electrochemical reduction of CO2 into 1-butanol with high faradaic efficiencies (42%) using what has been described as a Ni-enhanced Cr2O3–Ga2O3 modified glassy carbon electrode provides a new electrochemical methodology for CO2 utilization. Currently, the associated charge transfer dynamics and interfacial character that allow this reactivity are not well understood. Here, the electrochemical characteristics of the Cr2O3–Ga2O3 interface are explored using a toolkit of redox probes to study the electron transfer, proton transfer, and mass transfer characteristics of the electrode. Addition of the Cr2O3–Ga2O3 coating introduces a significant change in the electrochemical double layer characteristics, which is in part due to the underlying nanostructure of the oxide coating. This environment improves the electron and proton transfer rates, as well as increases the concentration of reactive species near the electrode. Much of this improvement is associated with the porous nonconducting nature of the oxide layer. These findings offer an improved understanding of the electrode and electrocatalytic nature needed to undertake the reduction of CO2 to produce carbon–carbon bonded products.