Electrodeposited chromium-doped α-Fe2O3 under various applied potential configurations for solar water splitting

Abstract

In this work, high quality hematite (α-Fe2O3) Chromium (Cr)-doped thin films have been synthesized via electrodeposition technique, on fluorine-doped tin oxide-coated glass substrates, under various applied potential configurations [cyclic voltammetry (CV), linear sweep voltammetry (LSV) and −0.5 V]. Chromium was added to the electrolyte at such a proportion that the Cr/(Cr + Fe) ratio remained within 8%. The as-deposited films were subsequently annealed in air at 650 °C for 2 h. Our novel study highlights the effect of using variable potential approaches during the film preparation on the properties of Cr-αFe2O3 deposited films. The prepared thin films were analyzed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV–Vis absorption and photoelectrochemical (PEC) analysis. XRD revealed that samples are crystallized in Cr-Fe2O3 cubic structure with a crystalline orientation in the plane (1 1 1) and a clear improvement of the crystallinity and size crystallite of the Cr-Fe2O3 deposited using CV process. SEM micrographs showed that the morphology grains were three-sided pyramid-shaped, expanding with increase of the crystallinity. The calculated band gap values are 2.18, 2.23 and 2.20 eV, respectively for −0.5 V, LSV, CV. The Cr-Fe2O3 films synthesized in this study showed high PEC activity with very low carrier density in comparison with the conventionally electrodeposited films. This Cr-doped hematite films ‘excellent photoelectrochemical performance was mainly attributed to improved charge carrier properties. Such high photoactivity was attributed to the large active surface area and increased donor density caused by increasing the Cr doping in the α-Fe2O3 films.