Surface charge modification for improvement of photocatalytic H2 production over a La2Ti2O7/graphene nanocomposite

Abstract

A La₂Ti₂O₇/graphene (GR) nanocomposite with intimate interfacial contact and a large contact area is synthesized by a facile electrostatic self-assembly approach. The nanocomposite is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and photoluminescence (PL) spectroscopy. The La₂Ti₂O₇/GR nanocomposite exhibits the highest H₂ production rate when used in photocatalytic water splitting, with an improvement of 5.7 and 4.9 times relative to pure La₂Ti₂O₇ and La₂Ti₂O₇/GR-H that was prepared without surface charge modification, respectively. In addition, the transient photocurrent responses and electrochemical impedance spectroscopy (EIS) results indicate that the La₂Ti₂O₇/GR nanocomposite exhibits more effective separation of photogenerated electron–hole pairs and faster interfacial electron transfer compared to pure La₂Ti₂O₇ nanosheets and the La₂Ti₂O₇/GR-H nanocomposite. The enhanced photocatalytic H₂ production rate and photo-electrochemistry activity can be ascribed to the intimate interfacial contact and large contact area between the La₂Ti₂O₇ nanosheets and GR, which help to make full use of the electron conductivity of GR for transferring photogenerated electrons, prolonging the lifetime of charge carriers and improving the rate of water splitting to form H₂.