Electrochemical study of TiO2 modified with silver nanoparticles upon CO2 reduction

A systematic cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) study on titanium dioxide (TiO2) and silver-TiO2 surfaces was performed in order to decouple electrochemical reduction processes of carbon dioxide in aqueous solutions. CV studies indicate cathodic current increase on Ag-TiO2 compared to bare TiO2 surfaces. An equivalent circuit based on transmission line model was applied in order to adjust EIS data, and a modification of this model was made to account for Ag particle interaction with the electrolyte solution. Electrochemical processes were then decoupled upon applied potential where the role of TiO2 surface states was identified and separated from (a) silver reduction, (b) electronic transport on TiO2, and (c) charge transfer on TiO2 and Ag surfaces. The Ag-electrolyte interface impedance has considerably lower values than the TiO2-electrolyte interface, suggesting that the silver particles may be considered as favorable reaction sites for the electrochemical reduction of water and carbon dioxide.