Interfacial charge dynamics in type-II heterostructured sulfur doped-graphitic carbon nitride/bismuth tungstate as competent photoelectrocatalytic water splitting photoanode.

Sluggish charge transfers at the electrode/electrolyte interface and fast recombination of electron-hole pairs limit the photoelectrocatalytic water-splitting ability of the bismuth tungstate (Bi2WO6). To address these issues, sulfur doped-graphitic carbon nitride/bismuth tungstate (S-g-C3N4/Bi2WO6) heterostructured hybrid material with different wt% of S-g-C3N4 were constructed via an ultrasonic approach. The formation of heterostructure offers well-separated electron-hole pairs, thereby improving the charge transfer process, and boosting water oxidation kinetics on the surface of modified electrodes. Electrochemical impedance analysis confirms the rapid charge transfer process and quick electrochemical reaction at the electrode/electrolyte interface, which quenches the charge recombination process. The S-g-C3N4/Bi2WO6 with 3 wt% of S-g-C3N4 photoanode delivers ~43, ~18 and ~2-folds higher applied bias photon-to-current efficiency than S-g-C3N4, Bi2WO6, and g-C3N4/Bi2WO6 (3 wt% of g-C3N4) photoanodes, respectively. From the combination of UV-Vis, XPS valance band, and Mott-Schottky analysis the plausible band edge positions of the Bi2WO6 and S-g-C3N4 were calculated. Based on the band structure, we have concluded that the S-g-C3N4/Bi2WO6 hybrid photoanode follows a type-II charge transfer mechanism to promote the photoelectrocatalytic water splitting ability.