Porous perovskite-lanthanum cobaltite as an efficient cocatalyst in photoelectrocatalytic water oxidation by bismuth doped g-C3N4

•Bi@g-C3N4 photoanode decorated with LaCoO3 cocatalyst for PEC water splitting.•Bi dopant improves the photoelectrocatalytic activity of g-C3N4 toward OER.•Bi@g-C3N4/LaCoO3 showed much more anodic photocurrent and more negative onset potential compared with g-C3N4 and Bi@g-C3N4.•Creation of effective charge cascade between Bi@g-C3N4 and LaCoO3 accelerates separation/transfer of photo-induced charge carriers. The electrophoretic loading of porous perovskite-lanthanum cobaltite (LaCoO3) on bismuth doped g-C3N4 (Bi@g-C3N4) as a novel photoanode was designed for the efficient photoelectrocatalytic water splitting. Before loading cocatalyst, the photoelectrocatalytic oxygen evolution of g-C3N4 was investigated with various amounts of Bi. The photoconversion efficiency enhanced more than 3.7 times for 3.6% Bi doped compared with that of the pristine g-C3N4. The Mott-Schottky plots showed the amount of band bending for Bi@g-C3N4 is more than that of g-C3N4 resulting in better electron transfer at the photoelectrode/electrolyte interface. By loading LaCoO3 on Bi@g-C3N4 photoanode, the photoconversion efficiency of 2.3% at 0.28 V (vs. RHE) was obtained under visible light which is more than that of Bi@g-C3N4 (0.92% at 0.48 V vs. RHE) alone. The high photocurrent density of 0.40 mA cm−2 was observed for Bi@g-C3N4/LaCoO3 photoanode as compared with Bi@g-C3N4 (0.17 mA cm−2) at the redox potential of O2/H2O. Also, Bi@g-C3N4/LaCoO3 photoanode represents a smaller arc radius in electrochemical impedance spectroscopy Nyquist plot compared with those of g-C3N4 and Bi@g-C3N4.