In situ chemical synthesis of g-C3N4/In2O3 semiconductor composites for photoelectrochemical water oxidation

Abstract

This paper employed the heat treatment method to obtain g-C3N4/In2O3 composite semiconductor following the deposition-precipitation technique. The physical characterization of the composite semiconductor included diffused reflectance spectroscopy (DRS), X-Ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). There have been significant and promising outputs regarding photoelectrochemical (PEC) activity and fair thermodynamic stability toward water oxidation reaction. The results showed that the composite semiconductor's photoelectrochemical properties were much superior to pristine g-C3N4 or In2O3. The optimized 5.0 ​wt% g-C3N4/In2O3 composite shows the best photocurrent output of 1.3 ​mA ​cm−2 vs Ag/AgCl at 1.2 ​V for water oxidation reaction having bath composition of 0.1 ​M Na2SO4, maintained at pH 7 using PBS under 35 ​mW ​cm−2 irradiation. The Mott-Schottky analysis under electrochemical impedance spectroscopy indicates n-type semiconductivity of the as-prepared composite semiconductors. In addition, the action spectra show ∼48% incident photon to current conversion efficiency (IPCE) for the optimized photoanode. The photocatalytic properties of the photocatalyst were assessed through photodegradation of methylene blue (MB) under UV-visible light irradiation, which follows first-order kinetics. The photodegradation rate constant of MB for g-C3N4 (5.0 ​wt%)/In2O3 is 0.0190 min−1, which is almost doubled as compared to pristine In2O3 (rate constant: 0.0110 min−1). The durability of the laboratory-prepared photoanodes in the PEC process was also investigated. The improved PEC performances derived from the transport of excited electrons from the conduction band of g-C3N4 to In2O3.