Increasing the Activity of Indium-Tin Oxide Electrodes via Electrochemical Surface Modification

Abstract Although transition metal electrodes are common, electrodes made of p-block elements are an emerging area of study; indium-tin oxide (ITO) on polyethylene terephthalate has been proposed as an alternative to expensive transition metal electrodes due to its low cost and commercial availability. ITO electrodes have been found to undergo reduction at cathodic potentials, causing the surface bound ITO particles to form an InSn alloy, limiting reproducibility across experiments. In this work, we show that the partial reduction of the ITO surface prior to use in electrochemical experiments improves electrochemical activity via tailoring of particle size on the electrode surface. Interestingly, modified electrodes are more sensitive than pristine ITO electrodes, as demonstrated by a 209% increase in sensitivity to nitrate (NO3-) reduction and enhanced reproducibility for NH4+ generation. This paper shows how the ability to control electrode surface morphology makes ITO more electrochemically active, as shown through a 77.7% decrease in charge-transfer resistance for modified ITO when compared to pristine electrodes through electrochemical impedance spectroscopy and a study of NO3- reduction behavior. The ability to customize ITO electrodes through partial surface reduction further justifies its use for a wide range of electrochemical applications.