The role of ceria/precious metal interfaces in catalysis

The popularity of ceria (CeO2) supports has been increasing over the last three decades on account of the rich redox chemistry of such an oxide. The ability to act as an oxygen buffer and switch the oxidation state of Ce depending on conditions implies that the role of this oxide goes beyond the conventional function of stabilizing nanoparticles. In fact, ceria can actively participate in catalytic reactions by interacting with the supported metal, in particular precious metals, promoting various types of dynamic processes that are beneficial for catalysis. This perspective put into light such interfacial synergy, and the effects in several catalytic processes, encompassing the most traditional applications up to the most modern reaction schemes

Into the carbon: A matter of core and shell in advanced electrocatalysis

Electrocatalysis, particularly related to fuel cell applications or other processes related to sustainability, has been steadily advanced by the design of new hierarchical materials involving two or more phases. One particularly appealing type of structure features metal species confined within carbon layers. These materials combine the benefits of the two components, which often work in synergy. However, given the intrinsic catalytic activity of carbon and the fact that the metal may be chemically inaccessible, in many cases, which of the two phases is the truly active site is not fully clear. Particularly for pure core–shell systems, where the metal is completely covered by carbon, the identification of the specific task of each component is not trivial. Many reported works on this type of bi-component catalyst are speculative in this regard. It is important for catalyst development that future studies on these systems will include a thorough cross-check of the reactivity aspects by means of combination of suitable techniques or experiments to unravel probable mechanisms and that assumptions are avoided.Electrocatalysis, particularly related to fuel cell applications or other processes related to sustainability, has been steadily advanced by the design of new hierarchical materials involving two or more phases. One particularly appealing type of structure features metal species confined within carbon layers. These materials combine the benefits of the two components, which often work in synergy. However, given the intrinsic catalytic activity of carbon and the fact that the metal may be chemically inaccessible, in many cases, which of the two phases is the truly active site is not fully clear. Particularly for pure core–shell systems, where the metal is completely covered by carbon, the identification of the specific task of each component is not trivial. Many reported works on this type of bi-component catalyst are speculative in this regard. It is important for catalyst development that future studies on these systems will include a thorough cross-check of the reactivity aspects by means of combination..

MATERIALI INNOVATIVI PER CONVERTITORI CATALITICI A BASE DI CERIA E ZIRCONIA

1995/1996IX Ciclo1968Versione digitalizzata della tesi di dottorato cartacea

Design of dye-sensitized TiO2 materials for photocatalytic hydrogen production: light and shadow

Visible light-driven production of fuels and value-added chemicals is currently one of the most intensely investigated research topics across various scientific disciplines, due to its potential to ease the World\u2019s dependence on fossil fuels. In this perspective, we recapitulate some of the main features of dyesensitized photocatalytic systems aimed at solar H2 production, focusing in particular on TiO2-based threecomponent assemblies with organic sensitizers. Relevant aspects include the structural and electronic properties of the sensitizers, the nature of the semiconductor and the hydrogen evolution catalysts, the role of the sacrificial donor and the effect of the reaction parameters on H2 production rate and stability. Besides presenting the most significant recent developments of the field, we also analyse some of its common practices in terms of experimental design, laboratory procedures and data presentation, trying to highlight their weaknesses and suggesting possible improvements. We then conclude with a short paragraph discussing the possible future development of this exciting research area

Photo‐Induced Radicals in Carbon Nitride and their Magnetic Signature

As a metal-free semiconductor, carbon nitride is a promising material for sustainable photocatalysis. From the large number of studies, it seems apparent that the photocatalytic activity is related to the number and type of defects present in the structure. Many defects are paramagnetic and photoresponsive and, for this reason, Electron Paramagnetic Resonance (EPR) spectroscopy is a powerful method to derive fundamental information on the structure – local, extended and electronic – of such defects which in turn impact the optical, magnetic and chemical properties of a material. This review aims at critically discussing the interpretation of EPR data of native and photoinduced radical defects in carbon nitride research highlighting strengths and limitations of this spectroscopic techniqu

Nanostructured Ceria: Biomolecular Templates and (Bio)applications

4Ceria (CeO2) nanostructures are well-known in catalysis for energy and environmental preservation and remediation. Recently, they have also been gaining momentum for biological applications in virtue of their unique redox properties that make them antioxidant or pro-oxidant, depending on the experimental conditions and ceria nanomorphology. In particular, interest has grown in the use of biotemplates to exert control over ceria morphology and reactivity. However, only a handful of reports exist on the use of specific biomolecules to template ceria nucleation and growth into defined nanostructures. This review focusses on the latest advancements in the area of biomolecular templates for ceria nanostructures and existing opportunities for their (bio)applications.Part of the described research was funded by the University of Trieste (FRA2021 to M.M.).openopenRozhin, Petr; Melchionna, Michele; Fornasiero, Paolo; Marchesan, SilviaRozhin, Petr; Melchionna, Michele; Fornasiero, Paolo; Marchesan, Silvi

Graphitic carbon nitride meets molecular oxygen: New sustainable photocatalytic ways for the oxidation of organic molecules

In recent years, organic chemists have taken a resolute step toward green photocatalytic synthesis. In this regard, the oxidation of organic compounds with molecular oxygen is one of the most important classes of transformations, as it increases molecular complexity while avoiding the use of toxic and harmful oxidants. To this aim, the development of new and efficient photocatalysts capable of driving valuable oxidative reactions in a sustainable manner is highly desirable. These novel photocatalytic systems need to be metal-free, easy-to-prepare, and potentially recyclable. Carbon nitride (CN) fulfills all these requirements because of its outstanding physicochemical properties, thus emerging as a promising heterogeneous photocatalytic platform. The growing popularity of this material is also substantiated by its fast and facile preparation from readily available and inexpensive molecular precursors. This Review aims at highlighting the recent advances in synthesis of carbon nitride-based materials and their applications in organic photocatalysis for the oxidation of organic molecules in presence of molecular oxygen. Lastly, forward-looking opportunities within this intriguing research field are mentioned

Photocatalytic Hydrogen Production: A Rift into the Future Energy Supply

Photocatalytic hydrogen (H2) production is a process that converts solar energy into chemical energy by means of a suitable photocatalyst. After the huge amount of systems that have been tested in the last forty years, the advent of nanotechnology and a careful design at molecular level, allow to obtain attractive activity, even using pure visible light. At the same time we are approaching reasonable photocatalyst stability in laboratory test, and the attention is paid to identify cost-effective photocatalysts that might find real applications. This Review provides a broad overview of the elementary steps of the heterogeneous photocatalytic H2 production, including an outline of the physico-chemical reactions occurring on semiconductors and cocatalysts. The use of different renewable oxygenates as sustainable sacrificial agent for the H2 production is outlined, in view of a transition from fossil fuels to pure water splitting. Finally, the recent advances in the development of photocatalyst are discussed focusing on the current progress in organic and hybrid organic/inorganic photocatalysts

Nb2O5-Based Photocatalysts

Photocatalysis is one potential solution to the energy and environmental crisis and greatly relies on the development of the catalysts. Niobium pentoxide (Nb2O5), a typically nontoxic metal oxide, is eco-friendly and exhibits strong oxidation ability, and has attracted considerable attention from researchers. Furthermore, unique Lewis acid sites (LASs) and Bronsted acid sites (BASs) are observed on Nb2O5 prepared by different methods. Herein, the recent advances in the synthesis and application of Nb2O5-based photocatalysts, including the pure Nb2O5, doped Nb2O5, metal species supported on Nb2O5, and other composited Nb2O5 catalysts, are summarized. An overview is provided for the role of size and crystalline phase, unsaturated Nb sites and oxygen vacancies, LASs and BASs, dopants and surface metal species, and heterojunction structure on the Nb2O5-based catalysts in photocatalysis. Finally, the challenges are also presented, which are possibly overcome by integrating the synthetic methodology, developing novel photoelectric characterization techniques, and a profound understanding of the local structure of Nb2O5

Green Approaches to Carbon Nanostructure-Based Biomaterials

The family of carbon nanostructures comprises several members, such as fullerenes, nano-onions, nanodots, nanodiamonds, nanohorns, nanotubes, and graphene-based materials. Their unique electronic properties have attracted great interest for their highly innovative potential in nanomedicine. However, their hydrophobic nature often requires organic solvents for their dispersibility and processing. In this review, we describe the green approaches that have been developed to produce and functionalize carbon nanomaterials for biomedical applications, with a special focus on the very latest reports