2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

Polydopamine and Its Derivative Materials: Synthesis and Promising Applications in Energy, Environmental, and Biomedical Fields

Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,‡ Vimlesh Chandra, Namdong Kim, K. Christian Kemp, Pavel Hobza,‡,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim* †Institute of Materials Science, NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310 Athens, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo naḿ. 2, 166 10 Prague 6, Czech Republic

Functionalization of Graphene: Covalent and Non-Covalent Approaches, Derivatives and Applications

Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO2) semiconductor materials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applications. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO2 photocatalytic materials. In this review, a background on TiO2 structure, properties and electronic properties in photocatalysis is presented. The development of different strategies to modify TiO2 for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed. Emphasis is given to the origin of visible light absorption and the reactive oxygen species generated, deduced by physicochemical and photoelectrochemical methods. Various applications of VLA TiO2, in terms of environmental remediation and in particular water treatment, disinfection and air purification, are illustrated. Comprehensive studies on the photocatalytic degradation of contaminants of emerging concern, including endocrine disrupting compounds, pharmaceuticals, pesticides, cyanotoxins and volatile organic compounds, with VLA TiO2 are discussed and compared to conventional UV-activated TiO2 nanomaterials. Recent advances in bacterial disinfection using VLA TiO2 are also reviewed. Issues concerning test protocols for real visible light activity and photocatalytic efficiencies with different light sources have been highlighted.

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A review on the visible light active titanium dioxide photocatalysts for environmental applications

Graphene based materials: Past, present and future

Recently sulfate radical-based advanced oxidation processes (SR-AOPs) attract increasing attention due to their capability and adaptability in decontamination. The couple of cobalt and peroxymonosulfate (PMS) is an efficient way to produce reactive sulfate radicals. This article reviews the state-of-the-art progress on various heterogeneous cobalt-based catalysts for PMS activation, including cobalt oxides, cobalt-ferrite and supported cobalt by diverse substrates. We summarize the intrinsic properties of these catalysts and their fundamental behaviors in PMS activation, as well as synthetic approaches. In addition, influencing factors and synergistic techniques of Co/PMS systems in organic degradation and possible environmental applications are also discussed. Finally, we propose perspectives on challenges related to cobalt-based catalysts, heterogeneous Co/PMS systems and their potential applications in practical environmental cleanup.

Cobalt-catalyzed sulfate radical-based advanced oxidation: A review on heterogeneous catalysts and applications

Graphene oxide/TiO2 composites were prepared by using TiCl3 and graphene oxide as reactants. The concentration of graphene oxide in starting solution played an important role in photoelectronic and photocatalytic performance of graphene oxide/TiO2 composites. Either a p-type or n-type semiconductor was formed by graphene oxide in graphene oxide/TiO2 composites. These semiconductors could be excited by visible light with wavelengths longer than 510 nm and acted as sensitizer in graphene oxide/TiO2 composites. Visible-light driven photocatalytic performance of graphene oxide/TiO2 composites in degradation of methyl orange was also studied. Crystalline quality and chemical states of carbon elements from graphene oxide in graphene oxide/TiO2 composites depended on the concentration of graphene oxide in the starting solution. This study shows a possible way to fabricate graphene oxide/semiconductor composites with different properties by using a tunable semiconductor conductivity type of graphene oxide.

Synthesis of visible-light responsive graphene oxide/TiO(2) composites with p/n heterojunction.

Co3O4/BiVO4 composite photocatalyst with a p−n heterojunction semiconductor structure has been synthesized by the impregnation method. The physical and photophysical properties of the composite photocatalyst have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transimission electron microscopy (TEM), BET surface area, and UV−visible diffuse reflectance spectra. Co is present as p-type Co3O4 and disperses on the surface of n-type BiVO4 to constitute a heterojunction composite. The photocatalyst exhibits enhanced photocatalytic activity for phenol degradation under visible light irradiation. The highest efficiency is observed when calcined at 300 °C with 0.8 wt % cobalt content. On the basis of the calculated energy band positions and PL spectra, the mechanism of enhanced photocatalytic activity has been discussed.

Efficient photocatalytic degradation of phenol over Co3O4/BiVO4 composite under visible light irradiation.

Metal-free carbonaceous materials, including nitrogen-doped graphene and carbon nanotubes, are emerging as alternative catalysts for peroxymonosulfate (PMS) activation to avoid drawbacks of conventional transition metal-containing catalysts, such as the leaching of toxic metal ions. However, these novel carbocatalysts face relatively high cost and complex syntheses, and their activation mechanisms have not been well-understood. Herein, we developed a novel nitrogen-doped carbonaceous nanosphere catalyst by carbonization of polypyrrole, which was prepared through a scalable chemical oxidative polymerization. The defective degree of carbon substrate and amount of nitrogen dopants (i.e., graphitic nitrogen) were modulated by the calcination temperature. The product carbonized at 800 °C (CPPy-F-8) exhibited the best catalytic performance for PMS activation, with 97% phenol degradation efficiency in 120 min. The catalytic system was efficient over a wide pH range (2–9), and the reaction of phenol degradation h...

Selective Degradation of Organic Pollutants Using an Efficient Metal-free Catalyst Derived from Carbonized Polypyrrole via Peroxymonosulfate Activation

The visible light induced photoelectrochemical properties of the pressed powder electrodes n-BiVO4, p-Co3O4, and n-BiVO4/p-Co3O4 containing 0.8 wt % cobalt were investigated. At pH 7 flatband potentials of −0.30 and +0.54 V vs NHE were measured for the bismuth vanadate and cobalt oxide, respectively, whereas −0.31 V was obtained for BiVO4/Co3O4. At a bias of 0.1 V vs Ag/AgCl the n-type photocurrent of BiVO4 changes to p-type upon prolonged irradiation, whereas it remains n-type at the much higher bias of 1.0 V vs Ag/AgCl. The change in conductivity type can be rationalized by invoking oxidation of water to a surface peroxide species. From the photocurrent decay of BiVO4 under chopped irradiation the presence of efficient charge recombination is indicated. It can be suppressed by addition of iodide, thiocyanate, or methanol, leading to about twice as large incident-photon-to-current efficiencies (IPCE). Different from that, in the case of the BiVO4/Co3O4 electrode the IPCE values do not change in the prese...

Mingce Long

Papers

Cobalt-catalyzed sulfate radical-based advanced oxidation: A review on heterogeneous catalysts and applications

Synthesis of visible-light responsive graphene oxide/TiO(2) composites with p/n heterojunction.

Efficient photocatalytic degradation of phenol over Co3O4/BiVO4 composite under visible light irradiation.

Selective Degradation of Organic Pollutants Using an Efficient Metal-free Catalyst Derived from Carbonized Polypyrrole via Peroxymonosulfate Activation

Visible Light Induced Photoelectrochemical Properties of n-BiVO4 and n-BiVO4/p-Co3O4