TiO2 photocatalysis and related surface phenomena

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

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

5.1. Nanoalloys of Group 11 (Cu, Ag, Au) 865 5.1.1. Cu−Ag 866 5.1.2. Cu−Au 867 5.1.3. Ag−Au 870 5.1.4. Cu−Ag−Au 872 5.2. Nanoalloys of Group 10 (Ni, Pd, Pt) 872 5.2.1. Ni−Pd 872 * To whom correspondence should be addressed. Phone: +39010 3536214. Fax:+39010 311066. E-mail: ferrando@fisica.unige.it. † Universita di Genova. ‡ Argonne National Laboratory. § University of Birmingham. | As of October 1, 2007, Chemical Sciences and Engineering Division. Volume 108, Number 3

Nanoalloys: From Theory to Applications of Alloy Clusters and Nanoparticles

Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

Oxide-based composites: applications in thermo-photocatalysis

The development of the photo-catalysis field is limited by a deficient quantitative assessment of photo-activity. The interplay between mass and momentum transport together with radiative transfer phenomena taking place at any photo-catalytic reaction or process makes complex such quantitative assessment. To reach this goal, the review studies the measurement, meaning, and analysis of three types of observables. The first family of observables has the reaction rate and closely connected observables as the turnover frequency as central pieces. The second family owns the so-called efficiency observables, starting from the photonic yield and quantum efficiency of the reaction and ending in the global efficiency of the process. Finally, the review studies kinetic constant observables. The contribution focusses on most rencet contribution analyzing these observables in terms of their (adequate) measurement conditions and physico-chemical interpretation, in order to unveil their full potential in the context of the photo-catalysis field. 

https://www.tandfonline.com/doi/pdf/10.1080/01614940.2022.2075535?needAccess=true

Recent progress in the quantitative assessment and interpretation of photoactivity

Series of nanosized anion-containing TiO 2 -base materials with anatase-type structure were synthesized from N, Cl-containing precursors using two preparation methods, calcination and hydrotreatment. Samples were conditioned by a final calcination step in order to get free of surface anion impurities and their structural properties characterized by a combined X-ray diffraction (XRD), scanning (SEM) and transmission (TEM) microscopy, X-ray energy dispersive (XEDS), X-ray photoelectron (XPS), and diffuse reflectance infrared Fourier transform (DRIFTS) study. The structural characterization was used to interpret the UV–vis spectra. The resulting joint information allowed the rationalization of the photocatalytic activity observed for the visible-light-assisted liquid-phase degradation of phenol. We founded that maximization of photoactivity is not related with the net absorption power of our systems in the visible range but mostly driven by a combination of two characteristics; the adequate morphological properties and the presence of negatively charged N-containing species.

Visible-light driven TiO2 photocatalysts from Ti-oxychloride precursors

Photocatalytic Nanooxides: The Case of TiO 2 and ZnO

In this work, the synthesis of the CuO-Cu2O nanocomposites decorated with TiO2 nanoparticles was performed by chemical-thermal oxidation and subsequently by the sol–gel method. The X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM) showed using different furnace atmospheres lead to the formation of nanocomposites with variable components content with a mixture of special morphology. The Energy Dispersive X-Ray Analysis (EDX) confirmed the existence of Ti, Cu, and O elements in the composite material. The X-ray photoelectron spectroscopy (XPS) data suggest the presence of CuO and Cu2O species in addition to the TiO2 phase in the as-prepared composite samples. Transmission electron microscopy (TEM) and UV–vis spectroscopy indicated the successful fabrication of multiple heterostructures of TiO2 and copper oxides components. The assessment of gas-phase photocatalytic performance in the 2-propanol photodegradation under both UV and visible light irradiation was done through the measurement of the reaction rate and quantum efficiency. The composite photocatalysts demonstrated about 2.5 times more active photocatalytic behavior in gas phase photo-oxidation compared with the pure CuO-Cu2O and titania because of the simultaneous presence of different copper oxide types in the structure and TiO2 nanoparticles as a surface decorated part. A cascade-type mechanism was also proposed for the photocatalytic behavior of the system. Furthermore, the stability of the specimens was proved during the photocatalytic reaction.

Marcos Fernández-García

Papers

Oxide-based composites: applications in thermo-photocatalysis

Recent progress in the quantitative assessment and interpretation of photoactivity

Visible-light driven TiO2 photocatalysts from Ti-oxychloride precursors

Photocatalytic Nanooxides: The Case of TiO 2 and ZnO

Titania-decorated copper oxide nanophotocatalyst powder: A stable and promoted photocatalytic active system