Optimization of Hematite to Improve PEC Performance in Water Splitting

Abstract

Thus far, semiconductor materials explored to achieve theoretical solar to hydrogen efficiency (STH), included cadmium selenide (CdSe), zinc oxide (ZnO), copper(I)oxide (Cu2O), tungsten trioxide (WO3) and hematite (α-Fe2O3). Of these materials, hematite has received much attention for photoelectrochemical water splitting attributed to its stability in aqueous solution, a small band gap of 1.90 eV-2.20 eV, non-toxicity and abundance. However, it has associated limitations such as high electron-hole recombination rate, short hole diffusion length (2-4 nm) accompanied by short excited lifetime of 10 ps, and poor minority charge carrier mobility of 0.1 cm2 V-1s-1, leading to low photocurrent during water splitting. Furthermore, hematite promises a maximum theoretical STH efficiency of ~16.8 %, with photocurrent densities above 12 mAcm-2, but the reported findings are far below 10 mAcm-2. Using interfacial layers , annealing and doping, we have prolonged lifetimes and increased the photocurrent. In this work, hematite thin films and nanostructures were synthesized using dip coating and spray pyrolysis.