In Situ Synthesis of Mixed-Phase WO3 on Nitrogen-Doped Graphene with Enhanced Photoelectric Properties

WO3/N-rGO composites with a phase-junction structure were prepared by hydrothermal methods. The formation of orthorhombic and monoclinic WO3 during the in situ synthesis of WO3 on nitrogen-doped graphene was demonstrated by X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) results demonstrated the successful doping of nitrogen atoms in graphene. The effect of N-rGO and phase-junction structure on the photoelectric properties was investigated by photoelectrochemical tests. In the I–t test results, WO3/N-rGO exhibited a photocurrent density of 0.204 mA/cm2, which was 5.8 and 2.6 times higher than those of WO3 and WO3/rGO, respectively. The electrochemical impedance spectroscopy (EIS) demonstrated that N-rGO and phase-junction structure reduce the electrochemical impedance of the composites. In the linear sweep voltammetry (LSV) and Mott–Schottky (MS) results, WO3/N-rGO exhibited the highest photocurrent (3.65 mA/cm2) intensity at 1.23 V bias and the largest carrier density (3.63 × 1020 cm–3), respectively. Possible electron-transfer mechanisms of the composite materials also have been discussed.