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Jincai Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Quantitative isotope measurements in Heterogeneous Photocatalysis and electrocatalysis
    Energy & Environmental Science, 2020
    Co-Authors: Yuhan Lin, Chaoyuan Deng, Yuchao Zhang, Chuncheng Chen, Jincai Zhao
    Abstract:

    Heterogeneous Photocatalysis and electrocatalysis have attracted tremendous interest in energy chemistry including CO2 reduction, N2 fixation, water oxidation, oxygen reduction, organic transformations, etc. The molecular-level understanding of reaction mechanisms in Photocatalysis and electrocatalysis is pivotal to facilitate these processes, and the quantitative isotope measurement provides such a toolbox. Herein, we summarize the theory of two kinds of important isotope measurements (i.e., kinetic isotope effect and isotope labeling methods) and then review their important applications in photocatalytic/electrocatalytic CO2 reduction, N2 fixation, water oxidation, oxygen reduction and organic transformations on Heterogeneous catalysts. Future prospects for quantitative isotope measurements are also presented.

  • probing paramagnetic species in titania based Heterogeneous Photocatalysis by electron spin resonance esr spectroscopy a mini review
    Chemical Engineering Journal, 2011
    Co-Authors: Chuncheng Chen, Zhaohui Wang, Jincai Zhao
    Abstract:

    Many paramagnetic species such as active surface sites, reactive oxygen species (ROS) and organic radicals derived from the photodegradation of organics were involved in the Heterogeneous Photocatalysis. Identification and characterization of these paramagnetic species are essentially conducted using electron spin resonance (ESR) techniques, which can provide a detailed understanding of the radical composition and structure on the basis of the unique feature of g, hyperfine, and superhyperfine tensors for each kind of radicals of interest. In the present review, the basic theoretical principles of the ESR technique and its application in the field of TiO2-based Heterogeneous Photocatalysis are generally summarized. Two experimental approaches typical of ESR-direct monitoring of paramagnetic species or sites and spin-trapping technique have been described with particular attention to the choices of spin traps. The general features of the ESR spectra of photoinduced charges, inorganic and organic radicals in photocatalytic events are presented and discussed. In addition, some remarks will be made about the use of ESR in revealing the origin of enhanced photocatalytic activities in the mixed phase titania (P25) and visible-light-response N-doped TiO2.

  • Probing paramagnetic species in titania-based Heterogeneous Photocatalysis by electron spin resonance (ESR) spectroscopy—A mini review
    Chemical Engineering Journal, 2011
    Co-Authors: Zhaohui Wang, Chuncheng Chen, Jincai Zhao
    Abstract:

    Many paramagnetic species such as active surface sites, reactive oxygen species (ROS) and organic radicals derived from the photodegradation of organics were involved in the Heterogeneous Photocatalysis. Identification and characterization of these paramagnetic species are essentially conducted using electron spin resonance (ESR) techniques, which can provide a detailed understanding of the radical composition and structure on the basis of the unique feature of g, hyperfine, and superhyperfine tensors for each kind of radicals of interest. In the present review, the basic theoretical principles of the ESR technique and its application in the field of TiO2-based Heterogeneous Photocatalysis are generally summarized. Two experimental approaches typical of ESR-direct monitoring of paramagnetic species or sites and spin-trapping technique have been described with particular attention to the choices of spin traps. The general features of the ESR spectra of photoinduced charges, inorganic and organic radicals in photocatalytic events are presented and discussed. In addition, some remarks will be made about the use of ESR in revealing the origin of enhanced photocatalytic activities in the mixed phase titania (P25) and visible-light-response N-doped TiO2

  • TERMINOLOGY, RELATIVE PHOTONIC EFFICIENCIES AND QUANTUM YIELDS IN Heterogeneous Photocatalysis. PART II: EXPERIMENTAL DETERMINATION OF QUANTUM YIELDS†
    Pure and Applied Chemistry, 1999
    Co-Authors: Angela Salinaro, Jincai Zhao, Hisao Hidaka, Alexei V. Emeline, V. K. Ryabchuk, Nick Serpone
    Abstract:

    In the preceding article [Pure Appl. Chem. 71, 303–320 (1999)] we examined two principal features of Heterogeneous Photocatalysis that demanded scrutiny: (i) description of Photocatalysis and (ii) description of process efficiencies. For the latter we proposed a protocol relative photonic efficiency which could subsequently be converted to quantum yields. A difficulty in expressing a quantum yield in Heterogeneous photochemistry is the very nature of the system, either solid/liquid or solid/gas, which places severe restrictions on measurement of the photon flow absorbed by the light harvesting component, herein the photocatalyst TiO2, owing to non-negligible scattering by the particulates. It was imperative therefore to examine the extent of this problem. Extinction and absorption spectra of TiO2 dispersions were determined at low titania loadings by normal absorption spectroscopy and by an integrated sphere method, respectively, to assess the extent of light scattering. The method is compared to the one reported by Grela et al. [J. Phys. Chem. 100, 16 940 (1996)] who used a polynomial extrapolation of the light scattered in the visible region into the UV region where TiO2 absorbs significantly. This extrapolation underestimates the scattering component present in the extinction spectra, and will no doubt affect the accuracy of the quantum yield data. Further, we report additional details in assessing limiting photonic efficiencies and quantum yields in Heterogeneous Photocatalysis.

Jeanmarie Herrmann - One of the best experts on this subject based on the ideXlab platform.

  • Titania-based true Heterogeneous Photocatalysis
    Environmental Science and Pollution Research, 2012
    Co-Authors: Jeanmarie Herrmann
    Abstract:

    Introduction This article recalls and demonstrates that Heterogeneous Photocatalysis belongs to Heterogeneous catalysis according to its initial history. There are criteria, which have to be imperatively taken into account to deal with true (photo-)catalytic reactions. The photocatalytic activity, chosen as the reaction rate, is governed by five physical parameters (mass of catalyst, wavelength, initial concentrations (or pressures) of the reactants, temperature (around room temperature), and radiant flux). Discussion Once performed in optimal conditions, the reaction has to be characterized with (a) its quantum yield (ratio of the reaction rate to the incident photon flux), (b) the turnover number (number of molecules converted per active site during a given time), and (c) the turnover frequency ( per second). The true catalytic nature demands that the conversion provides a number of converted molecules higher than the “stoichiometric threshold” defined as the number of the active sites initially present on the catalyst, i.e., that be much greater than 1, and possibly than at least two or three orders of magnitude. Eventually, a complete mass balance determination should be established for all elements. It is shown that the main reaction intermediates are radicals. All these concepts and principles are illustrated by various examples (selective mild oxidation reactions, water pollutants elimination, and air purification), leading to a list of recommendations for performing really true catalytic reactions.

  • Titania-based true Heterogeneous Photocatalysis
    Environmental science and pollution research international, 2012
    Co-Authors: Jeanmarie Herrmann
    Abstract:

    Introduction This article recalls and demonstrates that Heterogeneous Photocatalysis belongs to Heterogeneous catalysis according to its initial history. There are criteria, which have to be imperatively taken into account to deal with true (photo-)catalytic reactions. The photocatalytic activity, chosen as the reaction rate, is governed by five physical parameters (mass of catalyst, wavelength, initial concentrations (or pressures) of the reactants, temperature (around room temperature), and radiant flux).

  • Heterogeneous Photocatalysis an emerging technology for water treatment
    Catalysis Today, 1993
    Co-Authors: Jeanmarie Herrmann, Chantal Guillard, P Pichat
    Abstract:

    Abstract Heterogeneous Photocatalysis is capable of destroying many organic micropollutants in aqueous medium. The principle of the method and a brief survey of the relevant literature are presented. On the basis of studies on the degradation of various substituted aromatics in UV-irradiated TiO2 aqueous suspensions carried out principally in our laboratory, we indicate the kinetic characteristics of the method, the nature of the intermediates and the degradation pathways, as well as the influence of pH or common ions and other parameters. The photocatalytic recovery of noble metals and the detoxification of water containing certain inorganic ions are also described. The advantages and disadvantages of the photocatalytic method, which begins to be commercialized, are briefly discussed.

Zhaohui Wang - One of the best experts on this subject based on the ideXlab platform.

  • probing paramagnetic species in titania based Heterogeneous Photocatalysis by electron spin resonance esr spectroscopy a mini review
    Chemical Engineering Journal, 2011
    Co-Authors: Chuncheng Chen, Zhaohui Wang, Jincai Zhao
    Abstract:

    Many paramagnetic species such as active surface sites, reactive oxygen species (ROS) and organic radicals derived from the photodegradation of organics were involved in the Heterogeneous Photocatalysis. Identification and characterization of these paramagnetic species are essentially conducted using electron spin resonance (ESR) techniques, which can provide a detailed understanding of the radical composition and structure on the basis of the unique feature of g, hyperfine, and superhyperfine tensors for each kind of radicals of interest. In the present review, the basic theoretical principles of the ESR technique and its application in the field of TiO2-based Heterogeneous Photocatalysis are generally summarized. Two experimental approaches typical of ESR-direct monitoring of paramagnetic species or sites and spin-trapping technique have been described with particular attention to the choices of spin traps. The general features of the ESR spectra of photoinduced charges, inorganic and organic radicals in photocatalytic events are presented and discussed. In addition, some remarks will be made about the use of ESR in revealing the origin of enhanced photocatalytic activities in the mixed phase titania (P25) and visible-light-response N-doped TiO2.

  • Probing paramagnetic species in titania-based Heterogeneous Photocatalysis by electron spin resonance (ESR) spectroscopy—A mini review
    Chemical Engineering Journal, 2011
    Co-Authors: Zhaohui Wang, Chuncheng Chen, Jincai Zhao
    Abstract:

    Many paramagnetic species such as active surface sites, reactive oxygen species (ROS) and organic radicals derived from the photodegradation of organics were involved in the Heterogeneous Photocatalysis. Identification and characterization of these paramagnetic species are essentially conducted using electron spin resonance (ESR) techniques, which can provide a detailed understanding of the radical composition and structure on the basis of the unique feature of g, hyperfine, and superhyperfine tensors for each kind of radicals of interest. In the present review, the basic theoretical principles of the ESR technique and its application in the field of TiO2-based Heterogeneous Photocatalysis are generally summarized. Two experimental approaches typical of ESR-direct monitoring of paramagnetic species or sites and spin-trapping technique have been described with particular attention to the choices of spin traps. The general features of the ESR spectra of photoinduced charges, inorganic and organic radicals in photocatalytic events are presented and discussed. In addition, some remarks will be made about the use of ESR in revealing the origin of enhanced photocatalytic activities in the mixed phase titania (P25) and visible-light-response N-doped TiO2

Leonardo Palmisano - One of the best experts on this subject based on the ideXlab platform.

  • Energy Transfer in Heterogeneous Photocatalysis
    2019
    Co-Authors: Marianna Bellardita, Riccardo Ceccato, Sandra Dirè, Vittorio Loddo, Leonardo Palmisano, Francesco Parrino
    Abstract:

    Electron transfer reactions constitute one of the main pillars of chemistry and numerous examples can be found in nature and in technological applications. Energy transfer induced reactions are more elusive but equally important in phenomena related with natural photosynthesis and in general when light-matter interactions are relevant.   Heterogeneous Photocatalysis is generally considered based on electron transfer reactions. In fact, absorption of photons of suitable energy induces formation of photogenerated charges (electron and holes) which in turn initiate redox reactions through interfacial electron transfer to (or from) surface species. However, rare examples of photocatalytic reactions induced by prevailing energy transfer have been recently reported in literature. Investigation in this field may be still defined at a nascent level, and the mechanistic aspects of energy transfer, widely investigated in photochemistry of homogeneous or colloidal systems should be clarified in Heterogeneous Photocatalysis. In the manuscript the basic principles of energy transfer will be presented along with some known examples. These concepts will be inferred in the field of Heterogeneous Photocatalysis, by considering the excited solid semiconductor as the energy donor. Some rare examples of energy transfer induced Heterogeneous photocatalytic reactions will be presented along with some tentative mechanistic hypotheses.

  • Heterogeneous Photocatalysis: guidelines on experimental setup, catalyst characterization, interpretation, and assessment of reactivity
    Catalysis Reviews, 2018
    Co-Authors: Francesco Parrino, Vittorio Loddo, Leonardo Palmisano, Giovanni Palmisano, Vincenzo Augugliaro, G. Camera-roda, Sedat Yurdakal
    Abstract:

    Soon after the publication of the first pioneering works on Heterogeneous Photocatalysis, the number of papers on this topic continuously increased. This intriguing field of research is very comple...

  • Heterogeneous Photocatalysis for selective formation of high value added molecules some chemical and engineering aspects
    ACS Catalysis, 2018
    Co-Authors: Francesco Parrino, Vittorio Loddo, Elisa Garcialopez, Marianna Ellardita, G Marci, Leonardo Palmisano
    Abstract:

    This review deals with the parameters that influence Heterogeneous Photocatalysis (PC) for selective synthesis of high-value chemicals by itself or in combination with other technologies. In particular, the parameters related to the photocatalysts, such as crystallinity degree, type of polymorph, surface acid–base properties, exposure of particular crystalline facets, coupling of different semiconductors, position of the valence and conduction band edge, addition of doping agents, and those related to the reaction system, such as setup configuration and reactor geometry, type of solvent, type and amount of photocatalyst, affecting the selectivity toward specific products are described and discussed. The presented results highlight that a precise evaluation of the efficiency of the process is a challenging but necessary task to be approached in order to allow real applications of photocatalytic processes.

  • Heterogeneous Photocatalysis: a promising advanced oxidation process
    Current Trends and Future Developments on (Bio-) Membranes, 2018
    Co-Authors: Leonardo Palmisano, Marianna Bellardita, Vittorio Loddo, G. Camera-roda
    Abstract:

    Abstract This chapter briefly presents the fundamentals of the processes of Heterogeneous Photocatalysis (PC). In particular, Langmuir–Hinshelwood and Eley–Rideal models that are often used to model the kinetics of Heterogeneous photocatalytic reactions are described together with other models and equations derived. Moreover, some considerations about the dependence of the rate of PC on the light intensity, pH, and photocatalyst modification are done. Methods for photoreactor modeling are described, and the coupling of PC with other advanced oxidation processes (AOPs) using H2O2, O3, and peroxydisulfate is discussed. It is highlighted that coupling different technologies results in a real intensification of the global efficiency only for specific ratios of the rates of the single processes. The suitability of the practical application of the AOPs must be based on a precise process efficiency assessment, which, as the results show, is a challenging but necessary task.

  • Heterogeneous Photocatalysis from fundamentals to possible applications
    Catalysis Today, 2017
    Co-Authors: Leonardo Palmisano, Vittorio Loddo, Sedat Yurdakal
    Abstract:

    This special issue of Catalysis Today Journal, is dedicated to the career of Prof. Vincenzo Augugliaro, University of Palermo, Italy, in the occasion of his retirement in 2015. Prof. Vincenzo Augugliaro was Full Professor of Transport Phenomena at the University of Palermo (Italy) since 1994. He contributed to the fol- lowing research fields: chemical absorption kinetics, biochemical reactor modelling, diffusional kinetics in metallizing alloys and Heterogeneous Photocatalysis; in this last field he investigated on chemical kinetics of Heterogeneous photocatalytic systems, modelling of Heterogeneous photoreactors, radiation field in absorbing-reacting media and application of Heterogeneous pho- tocatalysis to syntheses processes. He published more than 150 papers in prestigious journals and many chapters in books and is co-author of 4 patents. Prof. Augugliaro was appreciated not only for his important achievements in the field of Heterogeneous Photocatalysis, but also for his great effort as mentor of many master and PhD chemical engineering students.\ud This special issue contains twenty-four original papers by researchers involved in various aspects of Heterogeneous Photocatalysis

Marta I. Litter - One of the best experts on this subject based on the ideXlab platform.

  • Mechanisms of removal of heavy metals and arsenic from water by TiO2-Heterogeneous Photocatalysis
    Pure and Applied Chemistry, 2015
    Co-Authors: Marta I. Litter
    Abstract:

    AbstractThis article is an overview of recent work performed in our laboratory on TiO2 Heterogeneous Photocatalysis of aqueous systems containing toxic forms of chromium, arsenic, lead, uranium and mercury. The cases of chromium and arsenic are treated in profundity. Photocatalytic treatments can convert the ionic species into their metallic solid form and deposit them over the semiconductor surface, or transform them into less toxic soluble species. When a transformation to the zerovalent state is possible, this allows the recovery of the metal from the waters, with an important economical return. Three types of mechanisms can be considered, all of them taking place through successive thermodynamically allowed monoelectronic electron transfer steps: (a) direct reduction by photogenerated electrons; (b) indirect reduction by intermediates generated by hole or hydroxyl radical oxidation of electron donors (reducing radicals); (c) oxidative removal by holes or hydroxyl radicals. Fundamentals of oxidative or reductive Heterogeneous Photocatalysis are described, with special emphasis on the role of organic donors present in the medium acting as synergists. This indicates the possibility of simultaneous treatment of pollutants of different chemical structure and properties present in the same medium.

  • The combination of Heterogeneous Photocatalysis with chemical and physical operations: A tool for improving the photoprocess performance
    Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2006
    Co-Authors: Vincenzo Augugliaro, Leonardo Palmisano, Marta I. Litter, Javier Soria
    Abstract:

    Heterogeneous Photocatalysis is a process of great potential for pollutant abatement and waste treatment. In order to improve the overall performance of the photoprocess, Heterogeneous Photocatalysis is being combined with physical or chemical operations, which affect the chemical kinetics and/or the overall efficiency. This review addresses the various possibilities to couple Heterogeneous Photocatalysis with other technologies to photodegrade organic and inorganic pollutants dissolved in actual or synthetic aqueous effluents. These combinations increase the photoprocess efficiency by decreasing the reaction time in respect to the separated operations or they decrease the cost in respect of Heterogeneous Photocatalysis alone, generally in terms of light energy. Depending on the operation coupled with Heterogeneous Photocatalysis, two categories of combinations exist. When the coupling is with ultrasonic irradiation, photo-Fenton reaction, ozonation, or electrochemical treatment, the combination affects the photocatalytic mechanisms thus improving the efficiency of the photocatalytic process. When the coupling is with biological treatment, membrane reactor, membrane photoreactor, or physical adsorption, the combination does not affect the photocatalytic mechanisms but it improves the efficiency of the overall process. The choice of the coupling is related to the type of wastewater to be treated. A synergistic effect, giving rise to an improvement of the efficiency of the photocatalytic process, has been reported in the literature for many cases.

  • Mechanism of degradation of nitrilotriacetic acid by Heterogeneous Photocatalysis over TiO_2 and platinized TiO_2
    Journal of Applied Electrochemistry, 2005
    Co-Authors: Carina A. Emilio, Raquel Gettar, Marta I. Litter
    Abstract:

    TiO_2-Heterogeneous Photocatalysis of nitrilotriacetic acid (NTA) at pH 2.5 was studied to establish the kinetic regime and the reaction mechanism. Pure Degussa P-25 and Hombikat UV100 commercial samples were compared. A Langmuirian behavior was observed over P-25. Platinization of the Hombikat sample (0.5 wt.%) caused an important increase on the photocatalytic rate with a change in the kinetics from zero order in the pure precursors to first order in the platinized sample. The nature of the intermediates and their evolution with time were compared on all systems. Glycine, iminodiacetic and oxamic acids have been identified in different proportions, together with ammonium and glycolic acid, depending on the catalyst used. The rapid depletion of NTA was not accompanied by a corresponding total organic carbon (TOC) reduction, but 84% of TOC decrease was obtained on P25 after 24 h, a very reasonable result for refractory compounds. A detailed mechanism is proposed for the photocatalytic reaction, suggested to be the same over the three catalysts here tested.

  • Mechanism of degradation of nitrilotriacetic acid by Heterogeneous Photocatalysis over TiO2 and platinized TiO2
    Journal of Applied Electrochemistry, 2005
    Co-Authors: Carina A. Emilio, Raquel Gettar, Marta I. Litter
    Abstract:

    TiO2-Heterogeneous Photocatalysis of nitrilotriacetic acid (NTA) at pH 2.5 was studied to establish the kinetic regime and the reaction mechanism. Pure Degussa P-25 and Hombikat UV100 commercial samples were compared. A Langmuirian behavior was observed over P-25. Platinization of the Hombikat sample (0.5 wt.%) caused an important increase on the photocatalytic rate with a change in the kinetics from zero order in the pure precursors to first order in the platinized sample. The nature of the intermediates and their evolution with time were compared on all systems. Glycine, iminodiacetic and oxamic acids have been identified in different proportions, together with ammonium and glycolic acid, depending on the catalyst used. The rapid depletion of NTA was not accompanied by a corresponding total organic carbon (TOC) reduction, but 84% of TOC decrease was obtained on P25 after 24 h, a very reasonable result for refractory compounds. A detailed mechanism is proposed for the photocatalytic reaction, suggested to be the same over the three catalysts here tested.