Structural and Optical Characterization of Electrochemically Deposited Indium Oxide Nanostructures for Photoelectrochemical Investigation

Abstract

Herein, we studied the effect of different precursor solution pH values on the crystal structure, morphology, and optical properties of high-purity In2O3 nanostructures for their possible photoelectrochemical application via the electrodeposition technique. The XRD result revealed predominant growth in the (222) plane with the highest intensity for the sample of pH 4; the grain sizes decreased with rising pH in the range from 28.03 to 36.89 nm, having the minimal value at pH 4. The micrographs showed highly crystalline nanostructures, with the densest morphology at pH 4, which was attributed to the lowering of the film growth rate as the pH rises. The energy band gap demonstrated a slight shrinkage with increasing pH in the range of 2.86–2.93 eV and the reflectance was dominant in the visible and near-infrared regions, with relatively low values for all of the film samples, showing a minimal value at pH 4, thus confirming it to be the optimal pH for a most suitable In2O3 electrode for photoelectrochemical application. The I–V properties measured under 100 W simulated illumination showed an enhanced photocurrent, which increases with rising pH in the range of 0.134–0.188 mA/cm2, making a peak with the electrode of pH 4. The electrochemical impedance spectra (EIS) of In2O3 were in firm agreement with earlier results. Overall, these results suggest that pH 4 is the optimum pH to obtain the best-quality In2O3 nanostructure for PEC application.