Recovering Indium Tin Oxide Electrodes for the Fabrication of Hematite Photoelectrodes

Abstract

Indium tin oxide (ITO) electrodes are widely used in basic and applied research as well as in commercial electronic devices. After a primary use, ITO electrodes are commonly wasted without further application. Herein, we recycled ITO electrodes previously used as anodes in organic photovoltaic devices in our group. These recycled electrodes were treated with piranha solution to obtain recovered ITO electrodes (ITOPS). Chemical and structural changes of ITOPS electrodes were evaluated using XPS, EDS, UV/VIS, XRD, SEM and cathodic polarization studies pointing out for a complete leach of indium from the structure leaving a conductive tin oxide-based electrode. Subsequently, these electrodes were used in the fabrication of hematite photoelectrodes by a two-step process of electrodeposition and annealing. Structural characterization of the deposited thin film was performed before and after annealing treatment with XDR, Raman spectroscopy and XPS. A hematite thin film deposited on an ITOPS substrate was successfully obtained from the thermal dehydration of akaganeite. SEM micrographs showed a homogeneous distribution of the hematite deposit. Under a 470 nm LED illumination, hematite photoelectrode achieved a photocurrent density of 223 μA cm−2 at 0.8 V vs SCE showing a potential second life for recycled ITO electrodes (ITOPS) as substrates for photoelectrocatalytic processes.