Photoelectrochemical Splitting of Water to H2 and O2 at n-Fe2O3 Nanowires and Nanocrystalline Carbon-Modified (CM)-n-Fe2O3 Thin Films

Abstract

Iron oxide n-Fe2O3 nanowire thin films were synthesized by thermal oxidation of Fe metal sheet (Alfa Co. 0.25 mm thick) in an electric oven then tested for their photoactivity. The photoresponse of the n-Fe2O3 nanowires was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which was found to be proportional to photocurrent density, jp. The optimized electric oven-made n-Fe2O3 photoelectrodes showed photocurrent densities of 1.32 mA cm-2 at measured potential of 0.0 V/SCE with photoconversion efficiency of 1.69 % at applied potential of 0.70 V vs Eaoc (electrode potential at open circuit conditions) under illumination intensity of 100 mW cm-2 from a Solar simulator with a global AM 1.5 filter. The photoactivity was improved upon incorporation of carbon into the lattice of n-Fe2O3 by flame oxidation at 850{degree sign}C. The carbon modified (CM)-n-Fe2O3 showed enhanced photocurrent response to 3.14 mA cm-2 at a measured potential of 0.0 V/SCE with an efficiency of 2.23% at applied potential of 0.52 V vs Eaoc. The nanocrystalline CM-n- Fe2O3 and n-Fe2O3 nanowires thin films were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM).