Photocatalysis

About: Photocatalysis is a research topic. Over the lifetime, 67088 publications have been published within this topic receiving 2145233 citations. The topic is also known as: photocatalyst.

Novel C3N4–CdS composite photocatalysts with organic–inorganic heterojunctions: in situ synthesis, exceptional activity, high stability and photocatalytic mechanism

Abstract: Novel organic–inorganic composites composed of two visible light responsive semiconductors of graphitic carbon nitride (C3N4) and CdS were successfully synthesized via an “in situ” precipitation–deposition method. The C3N4–CdS heterostructures were fabricated by depositing CdS nanoparticles onto the surface of C3N4. The morphology and optical property of compsoites can be tuned by adjusting the mass ratio of C3N4–CdS, which determines the enhanced level of photocatalytic activity. The optimum activity of 0.7C3N4–0.3CdS photocatalyst is almost 20.5 and 3.1 times higher than those of individual C3N4 and CdS for the degradation of methyl orange, and 41.6 and 2.7 fold higher for the degradation of 4-aminobenzoic acid, respectively. Moreover, its activity is also much higher than those of C3N4–TiO2 and CdS–TiO2 composites, as well as N-modified TiO2. Of special significance is that the present C3N4–CdS composites exhibit high stabilities under illumination, in contrast with CdS. The enhancement in both performance and stability should be assigned to the effective separation and transfer of photogenerated charges originating from the well-matched overlapping band-structures and closely contacted interfaces. Our work highlights that coupling semiconductors with well-matched band energies provides a flexible route to improve the activity and stability of photocatalysts, and gives ideas for the design and synthesis of other highly active and stable materials.

Photocatalytic Transformation of Organic Compounds in the Presence of Inorganic Anions. 1. Hydroxyl-Mediated and Direct Electron-Transfer Reactions of Phenol on a Titanium Dioxide−Fluoride System

Abstract: The effect of fluoride ions on the photocatalytic degradation of phenol in an aqueous suspension of TiO2 has been investigated. Fluoride ions displace surficial hydroxyl groups and coordinate surface-bound titanium atoms directly. For 0.01 M fluoride concentration and 0.10 g L-1 of TiO2 in the range pH 2−6, the degradation rate of phenol is up to 3 times that in the absence of fluoride ions. This behavior has been correlated with the computed surface speciation. The decrease in the degradation rate of phenol as a function of the substrate concentration observed in naked TiO2 at a high concentration of phenol (over 0.01 M) is largely diminished in the presence of fluoride ions. A photocatalytic model which takes into account the primary events and recombination reactions is able to account for these experimental results. The competition between OH-radical-mediated reaction versus direct electron transfer is discussed. Finally, under a helium atmosphere and in the presence of fluoride ions, phenol is slowly...

Electrochemically assisted photocatalysis: titania particulate film electrodes for photocatalytic degradation of 4-chlorophenol

Abstract: A commercially available TiO[sub 2] powder (Degussa P25) has been used to prepare thin particulate films on conducting glass plates. These semiconductor particulate films are photoelectrochemically active with properties similar to an n-type semiconductor. The recombination between the photogenerated charge carriers can be suppressed by applying an external anodic bias. Electron scavengers, such as oxygen, affect the photocurrent generation by competing for the photogenerated electrons. These particulate films provide a convenient method for accelerating the photocatalytic reaction by applying an external bias. For example, the rate of photocatalytic degradation of 4-chlorophenol greatly increases when the TiO[sub 2] particulate film electrode is maintained at an external anodic bias (0.6 V vs SCE) during the UV photolysis. 26 refs., 6 figs.

Kinetics of photocatalytic degradation of reactive dyes in a TiO2 slurry reactor

Abstract: The textile industry consumes considerable amounts of water during the dyeing and finishing operations. Dyes are extensively used and hence wastewaters discharged in rivers or public sewage treatment plants are highly contaminated. In this work, a detailed investigation of the adsorption and photocatalytic degradation of the safira HEXL dye, an anionic azo dye of reactive class, is presented. H 2 O 2 and UV light have a negligible effect when they are used on their own. The adsorption of dye on the semiconductor shows a strong dependence on the pH and follows a Langmuir adsorption model. The photodegradation kinetics is discussed in terms of the Langmuir–Hinshelwood model. The effect of pH, amount of photocatalyst, UV light intensity and hydrogen peroxide concentration is discussed. The relative photonic efficiency of the system is reported using phenol as a standard organic compound.

Highly efficient photocatalysts constructed by rational assembly of dual-cocatalysts separately on different facets of BiVO4

Abstract: Cocatalysts play important roles in promoting the catalytic reactions of semiconductor photocatalysts. Especially, deposition of dual cocatalysts, i.e., oxidation and reduction cocatalysts, onto a semiconductor photocatalyst can significantly improve its photocatalytic activity due to the synergetic effect of rapid consumption of photogenerated electrons and holes. However, in most cases, the cocatalysts are randomly deposited onto the semiconductor photocatalysts, where the cocatalysts cannot function fully. Herein, based on the findings that photogenerated electrons and holes can be spatially separated onto the different facets of BiVO4, we have successfully prepared two types of photocatalysts (M/MnOx/BiVO4 and M/Co3O4/BiVO4, where M stands for noble metals) with reduction and oxidation cocatalysts selectively deposited onto the {010} and {110} facets of BiVO4 by a photo-deposition method. Remarkably enhanced photocatalytic activities were observed for such assembled photocatalysts in control experiments of photocatalytic water oxidation and photocatalytic degradation of methyl orange and rhodamine B. In-depth investigations show that the enhanced photocatalytic performances are due to not only the intrinsic nature of charge separation between the {010} and {110} facets of BiVO4, but also the synergetic effect of dual-cocatalysts deposited onto the different facets of BiVO4. This work further proves the feasibility of the general concepts for approaching efficient artificial photosynthesis systems, namely, engineering of crystal-based photocatalysts by selective deposition of suitable reduction and oxidation cocatalysts onto the different facets of light absorbing semiconductor crystals.