Nano Au deposited mesoporous S,N-TiO2 (SNT) nanocomposites have been fabricated through deposition precipitation technique by employing urea as the hydrolyzing agent. To investigate the structural, optical, and electronic properties, the photocatalysts are characterized through X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoelectrochemical measurements. Here in addition to the co-catalyst nature of nano Au particles, surface plasmon resonance (SPR) effect in visible region enhances the light harvestation ability as well as transfer electrons to the conduction band of SNT. Furthermore, easy channelization of photogenerated charge carriers through sulfate facilitated redox couple makes the system more potential towards H2 evolution. TEM study exhibits well interconnective morphology in the matrix which helps easy channelization of electrons in the SNT nanocomposites. The photocatalytic activities have been evaluated for hydrogen generation under the irradiation of visible light and an enhanced activity has been observed for the Au promoted SNT due to the presence of nano Au particles, that is, 3.5 nm. The hydrogen generation activity of 3Au-SNT is nearly 9 times higher than that of neat SNT, and the energy conversion efficiency was found to be 17.6 %.

For the efficient utilization of visible light from solar light illumination, wormhole mesoporous N-doped TiO 2 modified with carbon and sulfur (abbreviated as N-TiO 2 @CS nanocomposites) have been fabricated using a sol-gel auto-combustion method. The prepared samples under different calcination temperatures were thoroughly characterized by XRD, TEM, FTIR, BET Surface area, UV-Vis DRS, XPS and PL. It has been demonstrated that in N-TiO 2 @CS nanocomposites, incorporated N in the crystal lattice of TiO 2 exist as N-Ti-O, sulfur exist as sulfate ions (S 6+ ) on the TiO 2 surface and carbon species were modified on the surface of the photocatalyst. N-doping narrows the band gap and sulfate species on the surface of TiO 2 act as cocatalyst. Moreover, the presence of surface carbon species enhances visible light harvesting and stimulates to separate photo generated charge carriers, which makes the system more potential towards photocatalytic application. The photocatalytic activities of the as prepared catalyst were evaluated for phenol degradation under visible light irradiation. The higher photocatalytic activity of the N-TiO 2 @CS nanocomposite calcined at 400 uC (STU400) is attributed to the synergistic combination of C, N and S atoms, the wormhole mesoporous frame with high surface area and high crystalline anatase phase of TiO 2 . The overall photocatalytic activity and the proposed mechanism are further confirmed through PL spectra and trapping of hydroxyl radicals.

A series of novel N,S-TiO2/g-C3N4 nanocomposite (abbreviated as TuT) photocatalysts has been synthesized via a facile, cost effective, in situ thermal induced polymerization method. The as-synthesized nanocomposites were thoroughly characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy (UV-Vis DRS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photo luminescence spectroscopy (PL). Using UV-Vis DRS, a gradual enhancement in visible light absorption towards the red end was observed for the xTuT photocatalyst in comparison to bare g-C3N4 (Tu). The result demonstrates that thermal reaction of a higher wt% of thiourea with respect to Ti precursor causes coupling of the N,S-TiO2 and g-C3N4 nanocomposite, however at a lower wt% only N,S-TiO2 forms. The photocatalytic activity has been evaluated through H2 evolution. The synergistic combination of small crystallite size, the crystalline anatase phase, enhanced visible light absorption ability, enhanced specific surface area and the effective charge separation properties of the 10TuT photocatalyst makes the system pivotal for photocatalytic H2 evolution under visible light irradiation.