Investigating the Role of Substrate Tin Diffusion on Hematite Based Photoelectrochemical Water Splitting System

Hematite (α-Fe2O3) nanostructures have been extensively studied as photo-anodes for the conversion of sunlight into chemical fuels by water splitting. A number of factors limit the photo-activity of pristine hematite nanostructures, including poor electrical conductivity and long penetration depth of light. Previous studies have shown that use of tin (Sn) as an n-type dopant can substantially enhance the photoactivity of hematite photoanodes by modifying their morphological, optical and electrical properties. This article presents impedance spectroscopic investigation of interplay between Sn-doping and the photoanode performance for photoelectrochemical water splitting using hematite nanostructure. Mott-Schottky measurements show that the Sn dopant serves as electron donor and increases the donor density of Sn-doped α-Fe2O3 nanostructured layer to 2.39 × 1019 cm-3. Photoelectrochemical impedance spectroscopy shows efficient photogenerated charge transfer from hematite to electrolyte in Sn-doped α-Fe2O3 nanostructure. The Sn-doped α-Fe2O3 nanostructure exhibit a photocurrent density of 1.2 mA/cm2 at 1.4 V versus RHE electrode.