One-step in situ calcination synthesis of g-C3N4/N-TiO2 hybrids with enhanced photoactivity

Abstract

A series of composites, based on graphitic carbon nitride and nitrogen-doped titanium dioxide (g-C₃N₄/N-TiO₂), were prepared by a solid-phase calcination process, in which a homogenous mixture containing melamine and TiN was calcined at 550 °C for 3 h in air. Various techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) characterized the as-prepared composites. The results suggested that nitrogen was incorporated into the TiO₂ lattice that formed the N–Ti bonds, which was followed by the successful combination of g-C₃N₄ with N-TiO₂. A red-shift of absorption edge in the light region and more absorption in the visible light region were observed for the prepared composites. The synthesized composites exhibited excellent photocatalytic activities, which were evaluated by the degradation of methylene blue (MB) after irradiation with visible light. Especially, g-C₃N₄/N-TiO₂ composites, prepared using melamine and TiN with a mass ratio of 1 : 1, showed the highest photocatalytic activity, and the corresponding rate of MB degradation was 0.028 min⁻¹, which was 1.9 times greater than that of N-TiO₂ (0.015 min⁻¹). Furthermore, the photoelectrochemical performances of the samples on illumination with UV-visible light were evaluated. Remarkable enhancement of photoelectrochemical response of g-C₃N₄/N-TiO₂ composites in UV-visible light, compared to pristine N-TiO₂, was noticed. The co-modifications of TiO₂ with N doping and g-C₃N₄ coupling resulted in an enhancement in the capacity of light absorption and an improvement in the transfer of charge carriers, which predominantly contributed to the improvement of photoactivity. This study develops a new and facile fabrication procedure for g-C₃N₄/N-TiO₂ hybrids and represents an important step in the improvement of solar energy conversion using cost-effective materials.