Enhanced charge separation in copper incorporated BiVO4 with gradient doping concentration profile for photoelectrochemical water splitting

Abstract BiVO 4 is one of promising materials that are stable, abundant, non-toxic and inexpensive for hydrogen production by water splitting. High recombination rate inside BiVO 4 was reported as a limiting factor for photoelectrochemical (PEC) performance of BiVO 4 photoanode. In this work, Cu incorporated BiVO 4 with gradient doping concentration profile was synthesized by depositing a CuO layer between BiVO 4 and FTO followed with annealing. Cu-doped BiVO 4 films with homogeneous concentration profile were prepared as a counter part to show the different behaviors between the gradient doping and homogeneously doping on charge transport and separation. It is found that the PEC performance of BiVO 4 electrode is significantly improved by gradient doping concentration profile in BiVO 4 layer, especially at the high applied bias range. While homogeneously doped BiVO 4 showed a decreased PEC performance as Cu element acts as a recombination center. Mott–Schottky test showed that the flat band level of CuO-BiVO 4 shifts negative slightly, which is beneficial for hydrogen production. While a positive shift is observed for homogeneously Cu-doped BiVO 4 which could be a result from the recombination centre nature of Cu in BiVO 4 . This work provide an efficient and inexpensive means to reduce charge recombination in BiVO 4 and improve its of solar water splitting efficiency.