Modification of hydrothermally synthesized α-Fe₂O₃ nanorods with g-C₃N₄ prepared from various precursors as photoanodes for hydrogen production

This report addresses the synthesis, characterisation, and photoelectrochemical performances of α-Fe₂O₃ nanorods decorated with g-C₃N₄. Photoanode composites were fabricated in a two-step procedure in which fluorine-doped tin oxide (FTO) glass was coated with α-Fe₂O₃ nanorods via a hydrothermal method, followed by incorporation of g-C₃N₄via a wet-impregnation method. In particular, the study investigates the effects of precursors of g-C₃N₄ (urea, dicyandiamide, and melamine) on the photoelectrochemical properties of the prepared α-Fe₂O₃/g-C₃N₄ films. The films were thoroughly analysed by means of X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared (FTIR) spectroscopy, and UV-vis spectrometry. The highest photoelectrochemical output of the nanorod composite films was achieved with the use of g-C₃N₄ synthesized from urea, generating 15.3 μA cm⁻² of photocurrent density as a result of better charge transfer driven by the formation of a semiconductor heterojunction. This is a staggering 12-fold improvement compared to the unmodified hematite nanorods which managed to only produce 1.2 μA cm⁻² of photocurrent density. The merits of g-C₃N₄ prepared from urea as the best semiconductor couple for α-Fe₂O₃ are driven by its unique crystallinity and morphology with significantly larger surface area than g-C₃N₄ prepared from other precursors. The addition of glycerol as a sacrificial agent further improves the photocurrent to ca. 24 μA cm⁻². The findings in this study show the potential of α-Fe₂O₃/g-C₃N₄ composites for sustainable photoelectrochemical hydrogen production.