Decoration of graphene oxide as a cocatalyst on Bi doped g-C3N4 photoanode for efficient solar water splitting

To enhance the solar photoelectrocatalytic water splitting, an effective photoanode was designed by electrophoretic depositing of graphene oxide (GO) on FTO/c-TiO2/[email protected]3N4. The photoelectrocatalytic performance of g-C3N4 was improved by Bi doping and GO loading as a cocatalyst on the surface of photoanode through the efficient charge cascade to increase an effective charge separation and reduce activation barriers for oxygen evolution reaction. The current–potential curve of [email protected]3N4/GO displayed about five and two times more photocurrent density (0.3 mA cm−2 at 1.23 V vs RHE) with respect to those of g-C3N4 and [email protected]3N4, following with a 110 and 80 mV cathodically shifted onset potential, respectively. The conduction band edge was calculated using the flat band potential of the photocatalysts which was estimated by Butler-Gartner model. GO loading leads to yield the photo-voltage of 176 mV compared with 81 and 113 mV for g-C3N4 and [email protected]3N4, respectively. The optimum of thickness of GO cocatalyst was 0.9 µm. If the thickness exceeds this optimum value, the recombination centers increase and active sites of photocatalytic layer are blocked. The charge separation and injection efficiency for [email protected]3N4/GO photoanode were determined by using H2O2 as an effective hole scavenger. Among fabricated electrodes, [email protected]3N4/GO electrode represented the lowest charge transfer resistance. The results showed that much improvement in photoelectrocatalytic performance was achieved by GO loading on the surface of photoanode with respect to Bi doping in the structure of photocatalyst.