In situ synthesis of ultrafine TiO2 nanoparticles modified g-C3N4 heterojunction photocatalyst with enhanced photocatalytic activity

To improve the redox performance and light absorption property, the 2D/0D g-C3N4/TiO2 heterojunction photocatalyst were successfully fabricated by co-annealing process based on melamine powder and ultrafine TiO2 nanoparticles (about 9.87 nm) obtained from electrochemical etching technology. The surface micromorphology, crystal structure, basic element composition, chemical structure, specific surface and optical performance were analyzed by SEM-EDS, TEM, HR-TEM, XRD, XPS, FTIR and Ultraviolet-visible diffuse reflection spectra (UV-vis DRS). The photocatalytic performance of g-C3N4/TiO2 photocatalyst was assessed by the degradation of tetracycline hydrochloride (TC) under simulated sunlight irradiation. The results showed that the obtained TiO2 powder had extremely smaller particle size and higher photocatalytic activity than commercial P25. The coupling of 0D TiO2 nanoparticles and 2D g-C3N4 nanosheet further promoted the visible light absorption performance of TiO2. The unique g-C3N4/TiO2 heterojunction photocatalyst exhibited remarkable photocatalytic performance for the degradation of TC, whose degradation rate could reach to 99.40% under 120 min irradiation. The kinetic constant of the g-C3N4/TiO2 photocatalyst was 1.48 times of that of TiO2. The ESP results confirmed center dot OH and center dot O-2(-) radicals produced in the photocatalytic process. This work could provide an effective reference for the fabrication of ultrafine TiO2 powder and binary heterojunction photocatalyst with excellent photocatalytic activity for organic pollutants degradation in water purification.