The PEC water splitting performance of the optimized photoanodes was evaluated by the light-chopped LSV curves under AM 1.5G irradiation (1 sun), as provided in Figure . The photocurrent response of all photoanodes increases with increasing applied bias. No dark current was observed in the light-off cycles, signifying that obtained currents only originate from the charge carriers generated upon illumination. The pristine BiVO4 possessed the lowest photocurrent density of 0.008 mA cm -2 at 1.23 V vs. RHE. This photoactivity was assigned to the granular structure of BiVO4 with an average particle size of 220 nm (Figure ) that is greater than the hole diffusion length (~100 nm) in BiVO4 , limiting its photocurrent due to the poor hole transport.