In-Situ-Reduced Synthesis of Ti³⁺Self-Doped TiO₂/g-C₃N₄Heterojunctions with High Photocatalytic Performance under LED Light Irradiation

Abstract

A simple one-step calcination route was used to prepare Ti(3+) self-doped TiO2/g-C3N4 heterojunctions by mixture of H2Ti3O7 and melamine. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy, and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) technologies were used to characterize the structure, crystallinity, morphology, and chemical state of the as-prepared samples. The absorption of the prepared Ti(3+) self-doped TiO2/g-C3N4 heterojunctions shifted to a longer wavelength region in comparison with pristine TiO2 and g-C3N4. The photocatalytic activities of the heterojunctions were studied by degrading methylene blue under a 30 W visible-light-emitting diode irradiation source. The visible-light photocatalytic activities enhanced by the prepared Ti(3+) self-doped TiO2/g-C3N4 heterojunctions were observed and proved to be better than that of pure TiO2 and g-C3N4. The photocatalysis mechanism was investigated and discussed. The intensive separation efficiency of photogenerated electron-hole in the prepared heterojunction was confirmed by photoluminescence (PL) spectra. The removal rate constant reached 0.038 min(-1) for the 22.3 wt % Ti(3+) self-doped TiO2/g-C3N4 heterojunction, which was 26.76 and 7.6 times higher than that of pure TiO2 and g-C3N4, respectively. The established heterojunction between the interfaces of TiO2 nanoparticles and g-C3N4 nanosheets as well as introduced Ti(3+) led to the rapid electron transfer rate and improved photoinduced electron-hole pair's separation efficiency, resulting in the improved photocatalytic performance of the Ti(3+) self-doped TiO2/g-C3N4 heterojunctions.

Novel Synthesis of Plasmonic Ag/AgCl@TiO2 Continues Fibers with Enhanced Broadband Photocatalytic Performance

“…The curve resolution of the Ti 2p signal of S-CTF indicates four different peaks. The peaks at binding energies of 458.2 and 463.9 eV belong to Ti 2p 1/2 and Ti 2p 3/2 of Ti 3+ , while the other two peaks at 458.7 and 464.4 eV belong to Ti 2p 1/2 and Ti 2p 3/2 of Ti 4+ [40]. Ti 3+ (and oxygen vacancy) in S-CTF was produced during the heat treatment by the reduction of TF (the removal of partial lattice oxygen) with organic matters in steam as a reducing atmosphere.…”

“…The transformation of electron-hole pairs is different from visible irradiation. According to the CB and VB edge potentials of TiO2 (−0.29 and 2.91 eV [40]) and AgCl (0.09 and 3.16 [55]), both TiO2 and AgCl are excited under UV irradiation. The generated holes of AgCl can easily inject into the VB of TF [41], and then yield •OH with adsorbed water molecules, or directly degrade organic pollutants such as the holes generated by TF.…”

“…These electrons participate in the formation of •O 2 − radicals. Moreover, the oxygen vacancy in TF is also beneficial to trap electrons and promote their separation under visible or UV light irradiation [40].…”

Fabrication of a Z-Scheme g-C3N4/Fe-TiO2 Photocatalytic Composite with Enhanced Photocatalytic Activity under Visible Light Irradiation

“…It is expected that coupling g-C 3 N 4 with TiO 2 would form a Z-scheme photocatalytic system and solve the problems normally encountered when using each of the semiconducting materials individually. In order to further improve the photocatalytic performance of the g-C 3 N 4 /TiO 2 composite under visible-light irradiation, attempts on developing composites, such as g-C 3 N 4 -Ti 3+ /TiO 2 and S-, N-, or Fe 3+ -doped TiO 2 /g-C 3 N 4 , have been made [21][22][23][24]. However, very few works have been done on the fabrication of g-C 3 N 4 and Fe-doped TiO 2 nanocomposite structures.…”

Template‐Free Macro‐Mesoporous TiO2/Carbon Nitride Interface for Visible‐Light‐Driven Photocatalysis

“…The C 1s XPS spectrum is deconvoluted into three peaks of B.E 283.8, 286.4, and 288.1 eV, corresponding to adventitious carbon, C—N—C, and C—(N) 3 bonding modes of g‐C 3 N 4 (Figure c) . The N 1s high‐resolution spectra displayed broad asymmetric peak, which can be fitted into four peaks appearing at B.E of 397.1, 398.8, 400.6, and 402.8 eV (Figure d), which are ascribable to characteristic C—N═C, N—(C) 3 , C—N—H, and N—H bonds, respectively . These XPS results clearly infer and support the successful formation of the mTiO 2 /g‐C 3 N 4 heterojunction.…”