Ultrathin insulating under-layer with a hematite thin film for enhanced photoelectrochemical (PEC) water splitting activity

An ultrathin SiO2 under-layer was inserted between the FTO substrate and the Ti-doped hematite film to suppress the reverse electron recombination from the FTO substrate to the hematite layer for improved photoelectrochemical activity of the hematite film during the photoelectrochemical (PEC) water splitting reaction. The reverse current of the SiO2 under-layered hematite thin film decreased from -0.075 mA cm(-2) to -0.035 mA cm(-2), with enhanced interfacial charge transfer and internal charge transport efficiencies. The hematite film with the ultrathin SiO2 under-layer showed a promising photocurrent density of 0.76 mA cm(-2) at 1.23 V vs. RHE under 1 sun illumination without hole scavenger materials during the PEC water splitting reaction.