In this study, graphene-based titanium dioxide and zinc oxide composites (TiO 2 -G, ZnO-G) were synthesized using a hydrothermal process. Materials were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, UV−vis spectroscopy, scanning electron microscopy, and transmission electron microscopy. Photocatalytic activity of the composite materials under simulated solar light was studied using phenol as a model compound. A ca. 30% improvement on the degradation performance by the TiO 2 -G composite (and ZnO-G) was observed when reaction rate constants were compared with TiO 2 (and ZnO) only. This demonstrates the positive effect of graphene on suppressing charge recombination and extending the light absorption range. Further improvement on the photocatalytic degradation rate of phenol was obtained by coupling the two composites, ZnO-G and TiO 2 -G. This is attributed to more efficient charge separation and longer lifetime of the charge carriers, which eventually enhances the photocatalytic activity. The optimum stoichiometric amount of each component was obtained experimentally. Systematic parametric studies were also performed to study the effect of catalyst loading, initial phenol concentration, solution pH, and solar light intensity. Complete solar degradation of 40 ppm phenol was achieved within 60 min while using the coupled ZnO-G/TiO 2 -G photocatalysts at the optimum conditions.

In this work, solar TiO 2 photocatalysis was used for sacrificial hydrogen generation from formaldehyde. Platinum was loaded onto a TiO 2 photocatalyst by a solar photodeposition method to suppress the electron/hole recombination process. The photocatalyst inside the reactor was irradiated from the top with a solar simulator. Photocatalytic hydrogen generation from formaldehyde was influenced by the solution pH, platinum loading (wt %) on TiO 2 , catalyst concentration, light intensity, and initial formaldehyde concentration. A Langmuir-type model fitted well with the experimental data, and the values of surface reaction rate constant, k, and the adsorption equilibrium constant, K, are 2.3598 × 10 −6 mol min −1 and 17.73 M −1 , respectively. Apparent quantum yield (QY) was higher for the UV light-driven hydrogen generation (10.91%) compared to the solar lightdriven hydrogen generation (1.24%).

No abstract

No abstract

Today, global warming and green energy are important topics of discussion for every intellectual gathering all over the world. The only sustainable solution to these problems is the use of solar energy and storing it as hydrogen fuel. Photocatalytic and photo-electrochemical water splitting and sacrificial hydrogen generation show a promise for future energy generation from renewable water and sunlight. This article mainly reviews the current research progress on photocatalytic and photo-electrochemical systems focusing on dye-sensitized overall water splitting and sacrificial hydrogen generation. An overview of significant parameters including dyes, sacrificial agents, modified photocatalysts and co-catalysts are provided. Also, the significance of statistical analysis as an effective tool for a systematic investigation of the effects of different factors and their interactions are explained. Finally, different photocatalytic reactor configurations that are currently in use for water splitting application in laboratory and large scale are discussed.

No abstract