UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .

Advanced Nanoarchitectures for Solar Photocatalytic Applications

Preceding work on photoelectrochemistry at semiconductor single-crystal electrodes has formed the basis for the tremendous growth in the three last decades in the field of photocatalysis at semiconductor powders. The reason for this is the unique ability of inorganic semiconductor surfaces to photocatalyze concerted reduction and oxidation reactions of a large variety of electron-donor and -acceptor substrates. Whereas great attention was paid to water splitting and the exhaustive aerobic degradation of pollutants, only a small amount of research also explored synthetic aspects. After introducing the basic mechanistic principles, standard experiments for the preparation and characterization of visible light active photocatalysts as well as the investigation of reaction mechanisms are discussed. Novel atom-economic C-C and C-N coupling reactions illustrate the relevance of semiconductor photocatalysis for organic synthesis, and demonstrate that the multidisciplinary field combines classical photochemistry with electrochemistry, solid-state chemistry, and heterogeneous catalysis.

Semiconductor Photocatalysis—Mechanistic and Synthetic Aspects

Converting solar energy into fuel via photo-assisted water splitting to generate hydrogen or drive CO2 reduction is an attractive scientific and technological goal to address the increasing global demand for energy and to reduce the impact of energy production on climate change. Engineering an efficient, low-cost photocatalyst is necessary to achieve this technological goal. A photocatalyst combines a photosensitiser and an electrocatalyst to capture light and accelerate the chemical reactions in the same device. In this perspective paper, we first describe the recent developments of some families of semiconductors that are attractive candidates for engineering photocatalysts. We then discuss the use of semiconductors as light harvesting agents, combined with a bio-catalyst, synthetic bio-mimetic molecular catalyst or synthetic all-inorganic catalyst, in photocatalytic hybrid systems for water splitting and CO2 reduction. To highlight the advantages of semiconductors for engineering efficient and robust photocatalysts, we compare these systems to examples of homogeneous photocatalytic systems constructed from molecular photosensitisers (dyes). We conclude that all-inorganic catalysts coupled to appropriate semiconductors look more promising for the construction of robust photocatalytic hybrid systems for producing solar fuels.

Recent advances in hybrid photocatalysts for solar fuel production

Titanium dioxide (TiO2) is one of the most widely investigated metal oxides due to its extraordinary surface, electronic and catalytic properties. However, the large band gap of TiO2 and massive recombination of photogenerated electron–hole pairs limit its photocatalytic and photovoltaic efficiency. Therefore, increasing research attention is now being directed towards engineering the surface structure of TiO2 at the most fundamental and atomic level namely morphological control of {001} facets in the range of microscale and nanoscale to fine-tune its physicochemical properties, which could ultimately lead to the optimization of its selectivity and reactivity. The synthesis of {001}-faceted TiO2 is currently one of the most active interdisciplinary research areas and demonstrations of catalytic enhancement are abundant. Modifications such as metal and non-metal doping have also been extensively studied to extend its band gap to the visible light region. This steady progress has demonstrated that TiO2-based composites with {001} facets are playing and will continue to play an indispensable role in the environmental remediation and in the search for clean and renewable energy technologies. This review encompasses the state-of-the-art research activities and latest advancements in the design of highly reactive {001} facet-dominated TiO2via various strategies, including hydrothermal/solvothermal, high temperature gas phase reactions and non-hydrolytic alcoholysis methods. The stabilization of {001} facets using fluorine-containing species and fluorine-free capping agents is also critically discussed in this review. To overcome the large band gap of TiO2 and rapid recombination of photogenerated charge carriers, modifications are carried out to manipulate its electronic band structure, including transition metal doping, noble metal doping, non-metal doping and incorporating graphene as a two-dimensional (2D) catalyst support. The advancements made in these aspects are thoroughly examined, with additional insights related to the charge transfer events for each strategy of the modified-TiO2 composites. Finally, we offer a summary and some invigorating perspectives on the major challenges and new research directions for future exploitation in this emerging frontier, which we hope will advance us to rationally harness the outstanding structural and electronic properties of {001} facets for various environmental and energy-related applications.

Highly reactive {001} facets of TiO2-based composites: synthesis, formation mechanism and characterization

Photocatalysis is of significant interest for a wide range of applications related to energy and environment, such as pollutant degradation and hydrogen production. We will provide a review of the relationship between photocatalyst properties and its photocatalytic performance, as well as the strategies for the enhancement of photocatalytic activity, in particular under solar/ambient/visible illumination. Common applications of photocatalysts will then be reviewed, and we will summarize existing problems and areas requiring further improvements.

Strategies for improving the efficiency of semiconductor metal oxide photocatalysis

TiO2 has three polymorphic forms: anatase, rutile, and brookite. Anatase usually has the highest photocatalytic activity under illumination of UV light; the activity can further be improved by coupling with rutile. The development of a general method for endowing commercial anatase and anatase–rutile composite TiO2 with visible-light response and concomitantly increasing their UV-light activity should dramatically expand their viability. To this end, doping of various transition metals and anions has been extensively studied. In particular iron, which is harmless and abundant in nature is an ideal candidate; however, the positive doping effect is only limited to TiO2 particles smaller than 10 nm in diameter. This limit mainly arises because the doping generates impurity and/or vacancy levels in the bulk, which act as the recombination centers. As an alternative, Kisch et al. have devised the photosensitization of TiO2 by surface modification with platinum(IV) chloride. This approach is attractive in that the visible-light response can be induced by the simple procedure without introduction of the impurity/ vacancy levels. Recently, the research groups of Ohno and Hashimoto have shown that the surface modification of rutile TiO2 with Fe 3+ by the impregnation method leads to high visible-light activities for the decomposition of model organic pollutants. However, the effect is small for anatase TiO2. On the other hand, we have developed the chemisorption–calcination cycle (CCC) technique, in which metal complexes are adsorbed by chemical bonds and the organic (ligand) part is oxidized by post-heating to prepare metal oxide clusters and ultrathin films at a molecular scale. Herein we show that the surface modification of two kinds of TiO2 particles (see the Experimental Section) with highly dispersed iron oxides by the CCC technique ((FeOx)m/TiO2) gives rise to a high level of visible-light-induced activity and greatly heightens the activity under UV-light irradiation. [Fe(acac)3] was adsorbed on the TiO2 surface by a partial ligand exchange between the acetylacetonate and surface OH groups [Equation (1)]

Titanium(IV) Dioxide Surface‐Modified with Iron Oxide as a Visible Light Photocatalyst

[Sn(acac)2]Cl2 is chemisorbed on the surfaces of anatase TiO2via ion-exchange between the complex ions and H+ released from the surface Ti–OH groups without liberation of the acetylacetonate ligand (Sn(acac)2/TiO2). The post-heating at 873 K in air forms tin oxide species on the TiO2 surface in a highly dispersed state on a molecular scale ((SnO2)m/TiO2). A low level of this p block metal oxide surface modification (∼0.007 Sn ions nm−2) accelerates the UV-light-activities for the liquid- and gas-phase reactions, whereas in contrast to the surface modification with d block metal oxides such as FeOx and NiO, no visible-light response is induced. Electrochemical measurements and first principles density functional theory (DFT) calculations for (SnO2)m/TiO2 model clusters (m = 1, 2) indicate that the bulk (TiO2)-to-surface interfacial electron transfer (BS-IET) enhances charge separation and the following electron transfer to O2 to increase the photocatalytic activity.

Tin oxide-surface modified anatase titanium(IV) dioxide with enhanced UV-light photocatalytic activity

This study first presents a “TiO2-based eco-catalyst” working in the dark and under visible-light irradiation for the degradation of environmental organic pollutants. Molecular scale cobalt(III) oxide clusters are formed on the surface of highly active anatase TiO2 nanoparticles (Co2O3–TiO2) by the chemisorption–calcination cycle method. Co2O3–TiO2 exhibits very high visible-light activities for the degradation of 2-naphthol and formic acid used as model organic pollutants. Unprecedented thermocatalytic activity is concomitantly endowed on TiO2 by the surface modification. Prolonging reaction time in the Co2O3–TiO2 photo- and thermo-catalyzed reactions leads to the decomposition of 2-naphthol and formic acid to CO2. The essential action mechanisms of the Co2O3 clusters in the photocatalysis and thermocatalysis of Co2O3–TiO2 were discussed on the basis of spectroscopic and electrochemical data.

Simultaneous induction of high level thermal and visible-light catalytic activities to titanium(IV) oxide by surface modification with cobalt(III) oxide clusters

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a synthetic heterocyclic seleno-organic compound, has been shown to act as a scavenger of reactive oxygen species (ROS). We have previously reported that interleukin-1 (IL-1) inhibited proteoglycan (PG) synthesis and induced the production of ROS in cartilage explants and isolated chondrocyte cultures. In this study, we report the protective effect of ebselen against IL-1-mediated inhibition of PG synthesis and ROS induction in cultured cartilage explants and chondrocytes. Ebselen also reversed the inhibition of PG synthesis in mechanically stressed cultured chondrocytes. These data suggest that the use of the antioxidant ebselen may be a useful tool for studying the mechanisms of cartilage degradation.

Hironori Yamamoto

Papers

Titanium(IV) Dioxide Surface‐Modified with Iron Oxide as a Visible Light Photocatalyst

Tin oxide-surface modified anatase titanium(IV) dioxide with enhanced UV-light photocatalytic activity

Simultaneous induction of high level thermal and visible-light catalytic activities to titanium(IV) oxide by surface modification with cobalt(III) oxide clusters

Effect of ebselen, a scavenger of reactive oxygen species, on chondrocyte metabolism.