The formation of surface fluorides on TiO2 (F−TiO2), which can be easily attained by a simple addition of F- to aqueous TiO2 suspensions, uniquely affects both photocatalytic reactions and photoelectrochemical behaviors. The fluoride adsorption is favored at acidic pH and greatly reduces the positive surface charge on TiO2 by replacing ⋮Ti−OH2 + by ⋮Ti−F species. Effects of surface fluorination on the photocatalytic reactivities are very different depending on the kind of substrates to be degraded. F−TiO2 is more effective than pure TiO2 for the photocatalytic oxidation of Acid Orange 7 and phenol, but less effective for the degradation of dichloroacetate. It is proposed that the OH radical mediated oxidation pathways are enhanced on F−TiO2, whereas the hole transfer mediated oxidations are largely inhibited due to the hindered adsorption (or complexation) of substrates on F−TiO2. As for the photocatalytic reduction, the dechlorination of trichloroacetate is much reduced on F−TiO2. The photocurrents collected in TiO2 suspensions, which are mediated by electron shuttles (methyl viologen or ferric ions), and short-circuit photocurrents generated on an illuminated TiO2/Ti electrode are also markedly reduced in the presence of F-. The surface ⋮Ti−F group seems to act as an electron-trapping site and to reduce interfacial electron transfer rates by tightly holding trapped electrons due to the strong electronegativity of the fluorine. Finally, elementary charge transfer processes on F−TiO2 and their implications to photocatalytic reaction pathway are discussed.

A) Pt-TiO 2 B) La-TiO 2 Figure S1. Energy dispersive X-ray spectroscopy (EDS) for A) Pt(II)-TiO 2 and B) La-TiO 2 . The spectrum of Pt(II)-doped TiO 2 showed no apparent signals for elemental Pt, which indicates that Pt ions or Pt metal are not located on or near the surface and that they are well incorporated into TiO 2 lattice. In case of the La-doped TiO 2 material, 0.5 ~ 1.0 wt.% of La was detected; this indicates that La ions are located in the near surface region.

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A variety of combinations of CdS, TiO 2 , and Pt in preparing the hybrid catalysts were studied for hydrogen production under visible light (l > 420 nm) irradiation. The preparation method sensitively influenced the activity of the ternary hybrid catalysts. The formation of the potential gradient at the interface between CdS and TiO 2 is necessary in achieving the efficient charge separation and transfer and how the platinum as a cocatalyst is loaded onto the CdS/TiO 2 hybrid catalysts determines the overall hydrogen production efficiency. The common method of photoplatinization of CdS/TiO 2 hybrid [Pt-(CdS/TiO 2 )] was much less efficient than the present method in which Pt was photodeposited on bare TiO 2 , which was followed by the deposition of CdS [CdS/(Pt-TiO 2 )]. The CdS/(Pt-TiO 2 ) has the hydrogen production rate ranging (6-9) Â 10, which is higher by a factor of 3-30 than that of Pt-(CdS/TiO 2 ). The photocatalytic activity of the ternary hybrid catalysts was extremely sensitive to where the platinum is loaded. The photoactivity of the hybrid catalyst was also assessed in terms of the photocurrent collected by the methyl viologen electron shuttle in the catalyst suspension. CdS/(Pt-TiO 2 ) generated higher photocurrents than Pt-(CdS/TiO 2 ) by a factor of 2-7. The extreme sensitivity of the preparation method to the hydrogen production activity should be taken into account when hybrid photocatalysts are designed and prepared.

Fluorochemicals (FCs) are oxidatively recalcitrant, environmentally persistent, and resistant to most conventional treatment technologies. FCs have unique physiochemical properties derived from fluorine which is the most electronegative element. Perfluorooctanesulfonate (PFOS), and perfluorooctanoate (PFOA) have been detected globally in the hydrosphere, atmosphere and biosphere. Reducing treatment technologies such as reverses osmosis, nano-filtration and activated carbon can remove FCs from water. However, incineration of the concentrated waste is required for complete FC destruction. Recently, a number of alternative technologies for FC decomposition have been reported. The FC degradation technologies span a wide range of chemical processes including direct photolysis, photocatalytic oxidation, photochemical oxidation, photochemical reduction, thermally-induced reduction, and sonochemical pyrolysis. This paper reviews these FC degradation technologies in terms of kinetics, mechanism, energetic cost, and applicability. The optimal PFOS/PFOA treatment method is strongly dependent upon the FC concentration, background organic and metal concentration, and available degradation time.

Perfluorinated chemicals (PFCs) are distributed throughout the environment. In the case of perfluorinated alkyl carboxylates and sulfonates, they can be classified as persistent organic pollutants since they are resistant to environmentally relevant reduction, oxidation, and hydrolytic processes. With this in mind, we report on the reductive defluorination of perfluorobutanoate, PFBA (C(3)F(7)CO(2)(-)), perfluorohexanoate, PFHA (C(5)F(11)CO(2)(-)), perfluorooctanoate, PFOA (C(7)F(15)CO(2)(-)), perfluorobutane sulfonate, PFBS (C(4)F(9)SO(3)(-)), perfluorohexane sulfonate, PFHS (C(6)F(13)SO(3)(-)), and perfluorooctane sulfonate, PFOS (C(8)F(17)SO(3)(-)) by aquated electrons, e(aq)(-), that are generated from the UV photolysis (lambda = 254 nm) of iodide. The ionic headgroup (-SO(3)(-) vs -CO(2)(-)) has a significant effect on the reduction kinetics and extent of defluorination (F index = -[F(-)](produced)/[PFC](degraded)). Perfluoroalkylsulfonate reduction kinetics and the F index increase linearly with increasing chain length. In contrast, perfluoroalkylcarboxylate chain length appears to have a negligible effect on the observed kinetics and the F index. H/F ratios in the gaseous fluoro-organic products are consistent with measured F indexes. Incomplete defluorination of the gaseous products suggests a reductive cleavage of the ionic headgroup occurs before complete defluorination. Detailed mechanisms involving initiation by aquated electrons are proposed.

Showcasing research from the group of Professor Wonyong Choi at Pohang University of Science and Technology (POSTECH).Photoinduced charge transfer processes in solar photocatalysis based on modifi ed TiO 2 Photocatalysis is being actively investigated as a core technology in solar light harvesting and utilizing processes. The basic process is driven by the photoinduced charge transfers (CTs) with initiating various redox reactions that are utilized for environmental remediation and solar energy storage. This Perspective article provides a comprehensive overview of the photoinduced CT events in bare and modifi ed TiO 2 , the most popular photocatalyst. Registered charity number: 207890 www.rsc.org/ees As featured in: See Wonyong Choi et al., Energy Environ. Sci., 2016, 9, 411. This journal is High efficiency solar photocatalysis requires an effective separation of photogenerated charge carriers and their rapid transport to the semiconductor interface. The mechanisms and kinetics of charge separation and interfacial/interparticle charge transfers (CT) are significantly influenced by both the bulk and surface properties of the semiconductor. The surface properties are particularly important because the photocatalysis should be driven by the interfacial CT. The most popular and the most investigated semiconductor photocatalyst is based on bare and modified TiO 2 . This article highlights the interfacial and interparticle CTs under the bandgap excitation of TiO 2 particles, visible light-induced photochemical processes via either dye-sensitization or ligand-to-metal CTs at surface modified TiO 2 particles, and the applications of the photo-processes to pollutant degradation and simultaneous hydrogen production.While a variety of surface modification techniques using various nanomaterials and chemical reagents have been developed and tested so far, their effects are very diverse depending on the characteristics of the applied photocatalytic systems and even contradictory in some cases. Better understanding of how the modification influences the photoinduced CT events in semiconductors is required, particularly for designing hybrid photocatalysts with controlled CTs, which is sought-after for practical applications of photocatalysis. Broader contextPhotocatalysis based on semiconductor materials is being actively investigated as a core technology in solar light harvesting and utilizing processes. The basic process is driven by the photoinduced charge transfers (CTs) occurring on the irradiated semiconductor surface with initiating various redox reactions that are utilized for environmental remediation and solar energy storage. The former reaction is usually initiated by a single electron transfer under aerated conditions to generate reactive oxygen species whereas the latter proceeds via two or more electron transfers in the absence of molecular oxygen. Most of the former reaction systems are thermochemically spontaneous (DG1 o 0) and lead to the mineralization of organic pollutants whereas the latter is an energy uphil...

Along with positive SARS-CoV-2 RNA in nasopharyngeal swabs, viral RNA was detectable at high concentration for >3 weeks in fecal samples from 12 mildly symptomatic and asymptomatic children with COVID-19 in Seoul, South Korea. Saliva also tested positive during the early phase of infection. If proven infectious, feces and saliva could serve as transmission sources.