One-Step Hydrothermal Deposition of Ni:FeOOH onto Photoanodes for Enhanced Water Oxidation

The realization of efficient photoelectrochemical (PEC) water splitting requires effective integration of earth-abundant active oxygen evolution catalysts (OECs) with diverse photoanodes. Although many good OECs have been investigated on conductive substrates under dark conditions, further studies are needed to evaluate their performance when integrated with photoanodes under illumination. Such studies will be facilitated by developing effective coating methods of OECs onto diverse photoanodes. Here, we report a one-step hydrothermal process that conformally coats various photoanodes with ultrathin Ni-doped FeOOH (Ni:FeOOH) OECs. The coated Ni:FeOOH, due to its unique open tunnel structure, tunable Ni doping concentration, and high coating/interface quality, lowers the onset potential of all of the photoanodes investigated, including WO3/BiVO4, WO3, α-Fe2O3, TiO2 nanowires, BiVO4 films, and Si wafers. We believe that this simple and yet effective hydrothermal method is a useful addition to the existing deposition techniques for coupling OECs with photoanodes and will greatly facilitate the scale-up of efficient PEC devices.