Enhanced sorption and photodegradation of chlorophenol over fluoride-loaded TiO2

Recent advances in surface and interface design of photocatalysts for the degradation of volatile organic compounds

Photocatalysis has attracted wide attention in eliminating volatile organic compounds (VOCs). This paper pays attention to the relationship between structure and performance of photocatalysts based on the fact that catalytic reactions arise on the surface of catalysts and the interface structure of photocatalysts plays key role in transfer efficiency of charges carriers. This review summarizes various surface/interface designs including unsaturated coordination such as oxygen vacancies, surface halogenations, and heterojunctions, homojunctions, facets, etc., as well as the application in photocatalytic degradation of VOCs. This paper reviews the influence of surface and interface properties of materials on VOCs molecules, effective strategies to promote the decomposition of VOCs from the perspectives of VOCs activation, reaction barrier etc., and presents various methods of photocatalyst design appropriately. The degradation path of highly toxic benzene VOCs are also summarized. In addition, the possible problems and suggestions for photocatalytic degradation of VOCs are proposed.

Brookite TiO2 photocatalyzed degradation of phenol in presence of phosphate, fluoride, sulfate and borate anions

A significant enhancement of phenol degradation over brookite TiO₂ in presence of phosphate, fluoride, sulfate and borate anions is reported.

Graphene oxide-CdS composite with high photocatalytic degradation and disinfection activities under visible light irradiation

Graphene oxide (GO)-CdS composites were synthesized via a novel two-phase mixing method successfully. CdS nanoparticles were uniformly self-assembled on GO sheets at water/toluene interface. The photocatalytic degradation (photodegradation) and disinfection activities of GO-CdS composites were investigated thoroughly. The results show that GO-CdS composites exhibit higher efficiency in photodegradation of various water pollutants than pure CdS nanoparticles under visible light irradiation. In addition, the interactions between GO sheets and CdS nanoparticles inhibit the photo-corrosion of CdS and leaching of Cd(2+). Only 3.5 wt% Cd(2+) of GO-CdS was leached out after photodegradation, while 38.6 wt% Cd(2+) of CdS was lost into aqueous solution. Furthermore, the disinfection activity of GO-CdS composites was investigated for the first time. Nearly 100% of both Gram-negative Escherichia coli (E. coli) and Gram-positive Bacillus subtilis (B. subtilis) were killed within 25 min under visible light irradiation. The excellent performances of GO-CdS composites can be attributed to that (1) effective charge transfer from CdS to GO reduces the recombination rate of photo-generated electron-hole pairs; (2) uniform deposition of CdS on GO sheets eliminates aggregation of CdS nanoparticles; and (3) the strong interactions between GO and CdS enhancing the durability of GO-CdS composites. Finally, the mechanism behind these excellent performances was verified by transient photocurrent measurement and further confirmed by ESR technique as well as employing a radical scavenging species - dimethyl sulfoxide (DMSO).

Molecularly imprinted photocatalyst with a structural analogue of template and its application

To realize selective mineralization of low-level chlorophenols (CPs) in the presence of high-level ordinary pollutants, molecularly imprinted polymers (MIPs) coated photocatalyst was prepared using substrate analog as template. The pseudo-template imprinted photocatalysts showed rapid decomposition ability toward a group of CPs. Based on the complete dechlorination and spectrophotometry, a new method was proposed to detect the total organochlorine on CPs in water samples. The method showed good linearity when the concentrations of the total organochlorine on CPs is in the range of 12.0-200.0μmolL(-1). The detection limit is 1μmolL(-1) for this method. When this method was applied to measure the total organochlorine of the CPs in both tap water and river water samples, an average recovery ranged from 96.3% to 105.1% was obtained with RSD values less than 5%. In this green and simple method, the common inorganic ions in water showed no interference for the detection. The determination of the total organochlorine on the CPs might be used for estimation of the toxicity and the persistence of the water samples.

Fluorinated semiconductor photocatalysts: tunable synthesis and unique properties

Semiconductor photocatalysts are of great significance in solar energy conversion and environmental remediation. To overcome serious drawbacks of these materials with respect to narrow light-response range and low quantum efficiency, a variety of strategies have been developed in the past decades to enhance the light harvesting and excitation as well as the charge transfer against recombination. In particular, fluorination of semiconductor photocatalysts can be employed to modify their surface and bulk properties, and consequently, to enhance their photocatalytic performance. This review presents a comprehensive description of the F-mediated synthesis and unique properties of fluorinated semiconductor photocatalysts, in particular titanium dioxide (TiO(2)). The available strategies for the synthesis of fluorinated photocatalysts include post-synthesis fluorination and in-situ fluorination. Depending on the synthesis route and conditions, it is possible to control the chemical nature of incorporated fluorine (such as adsorbed fluoride and lattice-doped fluorine) and the fluoride-mediated crystal modification and organization, which often results in exceptional surface and bulk physicochemical properties, giving rise to unique photocatalytic properties. Significantly, the surface fluorination induces unusual adsorption behavior and interfacial charge transfer dynamics, directly affecting photocatalytic redox properties of the surface-fluorinated photocatalysts. The lattice fluorine-doping, sole or cooperative with other complementary co-dopants, introduces special localized electronic structures and surface defect states, accounting for the exceptional visible-light photoactivity of the fluorine-doped photocatalysts. Finally, recent advances in the synthesis and properties of fluorinated photocatalysts are summarized along with perspectives on further developments in this area of research.