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MCM-48 cubic mesoporous materials containing CdS and spatially isolated titania nanoclusters were prepared in this study. Powder X-ray diffraction (XRD), nitrogen adsorption isotherm, transmission electron microscopy (TEM), atomic absorption spectrophotometry (AAS), UV–Visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) studies were employed for the characterization of the CdS containing Ti-MCM-48 mesoporous materials. In the current study, all the samples showed photocatalytic activity under visible light (λ > 400 nm) irradiation for production of hydrogen from splitting of water without Pt as a co-catalyst. The solar hydrogen evolution rate by visible light irradiation seemed to be dependent on CdS and TiO2 content and the most active photocatalyst produced hydrogen at a rate of 2.726 mmol/h/gcatalyst. The apparent quantum yield of the most active photocatalyst was estimated to be 36.3%.

Cobalt containing TiO2 mesoporous materials were prepared by Evaporation-Induced Self-Assembly (EISA) process. The resulting mesoporous materials were characterized using powder X-ray diffraction (XRD), nitrogen physisorption, Raman spectroscopy, diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). The photocatalytic activities of the mesoporous materials were investigated for hydrogen production under solar simulated conditions. The non-modified TiO2 sample produced only 4 μmole H2/g catalyst after 4 h of irradiation. In contrast, the Co containing mesoporous materials produced significantly higher amounts of hydrogen under identical conditions. The highest solar hydrogen evolution (634 μmole H2/g catalyst after 4 h of irradiation) was from the Co-TiO2-0.5 material. The physico-chemical characterization results indicate that the Co2+ ions are dispersed as oxide species on the surface of the mesoporous titania. These cobalt surface species act as trap sites preventing recombination of the charge carriers as shown by PL measurements. The addition of Co2+ ions to the synthesis mixture prevents the formation of anatase-to-rutile which favorably permits more solar hydrogen production.

A facile synthetic method (in as little as four hours) for simultaneously loading high amounts of titania (Si/Ti = 3) and Pd0 co-catalyst (0.1 wt.% per gram of total catalyst) in cubic mesoporous MCM-48 material was developed at room temperature. The solar simulated photocatalytic hydrogen evolution from photocatalysts containing Pd0 and TiO2 nanoclusters in periodic cubic MCM-48 and aperiodic mesoporous silica was compared. The results indicate that the periodicity of the mesoporous silica support, the oxidation state of Pd, the location and dispersion of Pd0 have a significant impact on the photocatalytic activity. Periodic cubic MCM-48 mesoporous silica containing Pd0 in close contact with titania exhibit superior hydrogen evolution rates compared to Pd0-TiO2 containing aperiodic mesoporous silica. The highly ordered and open three-dimensional mesoporous cubic MCM-48 support has high surface area and facilitate good dispersion and close contact of titania and Pd0. At very low loadings of 0.1 wt.% of Pd, hydrogen yield was found to be 560 μ mol h−1, which is among the highest reported in the literature for Pd0 containing TiO2 based materials under solar simulated conditions. The results suggest that the pore architecture of the support is also an important parameter that governs the photocatalytic activity. In addition, the Pd0-mesoporous materials in general possess higher activity than Pd2+ containing mesoporous materials. The photocatalysts were extensively characterized by a variety of techniques such as powder X-ray diffraction (XRD), nitrogen sorption analysis, transmission and scanning electron microscopic studies, photoluminescence, diffuse reflectance spectroscopy (DRS), CO Chemisorption, and X-ray photoelectron spectroscopy (XPS).

We report a facile method for the synthesis of 4-mercaptobenzoic acid (MBA) stabilized CdS-trititanate nanotube (CdS-TNT) composite materials. The resultant materials were well characterized by powder X-Ray Diffraction (XRD), N2 physisorption, Raman spectroscopy, UV–Visible Diffuse Reflectance spectroscopy (DRS), Fourier-Transform Infra-Red (FT-IR) spectroscopy, Photoluminescence (PL) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Atomic Absorption Spectroscopy (AAS), and Transmission Electron Microscopy (TEM). The photocatalytic performances of these materials were evaluated by monitoring the amount of hydrogen evolved from water under visible light irradiation. The amount of hydrogen evolved from MBA stabilized CdS-TNT composite materials were higher compared to MBA stabilized CdS, suggesting an important role of the TNT support. The enhanced photocatalytic hydrogen generation in MBA stabilized CdS-TNT composite materials compared to CdS-MBA might have arisen from the effective charge separation in CdS-TNT composite materials, which was further supported by PL studies.

The dependence of electrooxidation on experimental conditions of organic molecules was investigated to optimize the production of hydrogen from potential wastewater sources using low voltage sources (∼1 V dc). Electrooxidation on platinum, gold, and stainless steel anodes with hydrogen production on the cathode was investigated using several different organic reductants, including: methanol, ethanol, glycerol, isopropanol, propanal, glycerol, glucose, sucrose, citric acid, and propionic acid. The electrolyte pH was varied from 2 to 12 in a 1 M Na2SO4 supporting solution. At 1 V, glycerol, citric acid, ethanol and methanol were found to yield the highest currents at low pH values (pH 2 and 7) on platinum electrode, glucose on gold electrode at pH 12 in 1 M Na2SO4 solution produced the highest total current density at 1 V with measured Faradaic efficiency for 1 M glucose of 70%. The hydrogen energy production efficiency was 86%. Practical limitations of glucose oxidation at optimum experimental conditions are discussed. Highlights: We determined optimal conditions for organic wastewater electrooxidation at 1 V. 3 mA/cm2 current density for glucose on Au electrode at 0.5 M and pH 13 obtained. Faradaic efficiency of H2 production was ∼70% for glucose on the Au electrode. These experiments are an alternative to the conventional water photoelectrolysis.

We report a green and facile approach for the preparation of carbon-modified (C-modified) TiO2 composite materials by hydrothermal synthesis followed by pyrolytic treatment. The resultant materials were characterized by powder X-ray diffraction (XRD), nitrogen physisorption studies, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). The photocatalytic performances of these materials were evaluated by calculating the amount of hydrogen evolved from the decomposition of water under solar simulated irradiation conditions. An improvement was achieved from no H2 evolution at all with the bare TiO2, to an evolution of 0.21 mL g−1 h−1 from a composite material modified with an optimum carbon loading of 3.62%. These results suggested that the interaction of carbon with predominantly rutile form of TiO2 can promote shallow trapping of photogenerated electrons in the oxygen vacancies. This phenomenon consequently enhances the photocatalytic activity by minimizing charge carrier recombination, a characteristic demonstrated by fluorescence quenching of the TiO2 emission.