The role of doping molybdenum (Mo) and back-front side illumination in enhancing the charge separation of α-Fe2O3 nanorod photoanode for solar water splitting

Abstract

Hematite (α-Fe2O3) has abundant reserves and an appropriate bandgap of ~2.1 eV for H2 production using water splitting. However, its potential application to solar water splitting is seriously limited by the extremely high charge recombination rate of the charge carriers. The present work investigates the photoelectrochemical (PEC) performance of molybdenum (Mo) doped α-Fe2O3 thin-film electrodes. The Mo-doped α-Fe2O3 samples were prepared by a hydrothermal method and then loaded with different Mo ratio to optimize the photocurrent density. The morphological characterization and crystal structure identified by FE-SEM, Raman, XRD, XPS and UV–vis analyses. Mo doping of α-Fe2O3, significantly enhanced the photocurrent density. The α-Fe2O3 film with optimized Mo-doped amount (10% Mo-doped α-Fe2O3) had a photocurrent density of 0.75 and 1.2 mA cm−2 in front and back-side illumination, respectively at 0.6 V versus Ag/AgCl under 100 mWcm−2 with an electrolyte of 1 M (pH = 12) aqueous NaOH solution, which are ~10 and 17 times higher than that of the pure α-Fe2O3 photoanode. The doping of Mo onto pure α-Fe2O3 increased the donor concentration 1.3-fold, reduced the width of the space charge layer (WSCL) 1.2-fold, and decreased the flat band potential (Vfb) 1.6-fold, which improved the photoelectrochemical efficiency.