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Journal ArticleDOI

Mechanism of photoelectrocatalytic dehydrogenation of 2-propanol on a polycrystalline ZnO photoelectrode

01 Dec 1983-Electrochimica Acta (Elsevier)-Vol. 28, Iss: 12, pp 1869-1874

AbstractThe mechanism of photoelectrocatalytic dehydrogenation of 2-propanol on a ZnO photoelectrode is re-examined. The effect of gaseous atmosphere is studied. The change of pH due to the reaction is followed under different experimental conditions. The larger part of the dissolution of ZnO occurs in the dark itself due to the solubility of ZnO. The photodissolution is comparatively small. 2-Propanol inhibits the photocorrosion slightly. H2O2 is detected in the electrolyte irrespective of the presence of 2-propanol. An electron transfer process followed by a free radical mechanism for the formation of H2O2 is proposed and discussed. more

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Journal ArticleDOI
Abstract: The photocatalytic degradation of isothiazolin-3-ones has been studied using the catalytically active TiO2 and ZnO and the inactive paint grade TiO2, under various illumination and chemical conditions. The reaction follows a pseudo-first-order kinetics. Three types of lamps have been used. The photocatalytic degradation is faster under UV lamp, when it is compared to reaction under suntest and fluorescent lamps. In the presence of oxygen and H2O2, the reaction proceeds faster than in air atmosphere. ZnO exhibits comparable activity with TiO2 and in some cases it was found to be even better than TiO2. The reaction was studied in aqueous suspensions as well as on gas–solid interfaces. The degradation of isothiazolin-3-ones in paint formulations was also studied.

143 citations

Journal ArticleDOI
TL;DR: The results showed that by using acetylacetone as the hydrolysis control agent, the formed TiO2 sol had relatively high stability and had the properties of super-hydrophilicity and anti-fogging capability, which indicated its excellent self-cleaning property.
Abstract: TiO2 sol was produced by the sol-gel method through the hydrolysis and the aging of tetrabutyl titanate and the TiO2 film was obtained by dipping and uniform lifting of the acid-treated and ultrasound-treated clean glass slides into the TiO2 sol followed by aging, drying, and calcination. The effect of the hydrolysis control agents to the formed sol was researched and the crystalline state, the morphology, and the photocatalytic properties of the products after calcination were characterized. The structural morphology, the contact angles before and after illumination, and the self-cleaning properties of the TiO2 film were characterized as well. The results showed that by using acetylacetone as the hydrolysis control agent, the formed TiO2 sol had relatively high stability. The product after the calcination of the TiO2 sol was of single anatase type with crystalline size of 18–20 nm and it could degrade nearly 100% of methylene blue after 90 min illumination. The formed TiO2 film is compact, continuous, smooth, and had the properties of super-hydrophilicity (after 30 min illumination due to its contact angle decreasing from 21° to nearly 0°) and anti-fogging capability, which indicated its excellent self-cleaning property.

29 citations

Book ChapterDOI
01 Jan 2014
Abstract: Interest in heterogeneous photocatalysis has heightened in the past 40 years, underscoring several perspectives and advances. A collection of applications including solar to fuel cells, intelligent ink and remote photocatalysis have been closely examined. As an emerging panacea for the treatment of recalcitrant pollutants, heterogeneous photocatalytic degradation has been highlighted with specific reference to synthetic aliphatic and aromatic organic substances. What’s more, various treatment technologies for integration with photocatalytic degradation have been outlined.

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Journal ArticleDOI
Abstract: NUMBERS 16 and 17 in the Advances series have made their appearance. The titles are: "A Key to Pharmaceutical and Medicinal Chemistry Literature" and "Training of literature Chemists." The first is a collection of papers presented before the Divisions of Chemical Literature and Medicinal Chemistry; the second consists of papers given before a joint meeting of the Divisions of Chemical Education and Chemical Literature. Glancing at the titles of subjects covered to date in the Advances series, it becomes evident that a substantial literature is being built by literature chemists, largely through the divisions in the AMERICAN CHEMICAL SOCIETY. Number 4, "Searching the Chemical Literature," has been reprinted several times and frequently is referred to as the "bible" of literature chemists. Number 10, "Literature Resources for Chemical Process Industries," is in much demand. Nomenclature is a subject of direct importance to the literature chemist, and Number 8, entitled "Chemical Nomenclature," and ...

3,188 citations

Journal ArticleDOI
Abstract: The principles and applications of semiconductor electrodes in photo-electrochemical (PEC) cells (liquid junction photovoltaic, photoelectro-synthetic, photocatalytic) are described. Factors important to the design of practical systems and the extension of the principles of PEC cells to particulate systems for carrying out heterogeneous photocatalysis and photosynthesis are discussed. A “dual n-type semiconductor” model of biological photo-synthesis is proposed and possible means of utilization of such a system is described.

701 citations

Journal ArticleDOI
Abstract: In contrast to metals, the average free energy of electrons can be changed in semiconductors to a great extent by illumination Especially the concentration of minority electronic carriers can differ by orders of magnitude from the equilibrium value This has two major effects on electrode processes: (a) change of charge distribution and potential drops in the space charge layer; and (b) variation of the rate of electrode reaction in which minority carriers are involved Some examples are given for those effects at various semiconductors

249 citations

Journal ArticleDOI
Abstract: Photoelectrochemical devices for conversion of solar energy into both electrical energy and chemical energy are discussed with emphasis on how the various material properties of the photoactive electrodes influence device efficiency and stability. The similarity between photoelectrochemical cells (PECs) and solid state devices is used to model their behaviour and optimize such parameters as band gap, doping level, minority carrier lifetime, etc. A model is presented which calculates the electron affinity of any semiconductor and allows the prediction of the open circuit voltage of wet photovoltaic cells and optimum biasing forchemical producing cells. The effects of absorbed ions at the semiconductor/electrolyte interface are reviewed. The temperature dependence of the energy levels in the semiconductor and the electrolyte are considered and the implications of these results to operation of PECs at elevated temperature are discussed. The major differences between PECs and solid state devices are the stability considerations. The thermodynamics of this problem is discussed. Other important degradation mechanisms and some solutions to these problems are reviewed. Finally, a prognosis of the future of this field is presented.

224 citations

Journal ArticleDOI
Abstract: The role of the electronic properties of a semiconductor in heterogeneous catalysis and electrochemistry was experimentally investigated on single‐crystal ZnO. It was shown quantitatively that the availability of electrons and holes at the surface is dominant in the mechanism of a heterogeneously catalyzed reaction. Chemical rate measurements as well as in situ solid‐state measurements were carried out in an aqueous medium for the reaction: HCOOH+O2→H2O2+CO2, photocatalyzed by ZnO. Two new experimental electrochemical methods for semiconductor surface reactions were developed: ``current doubling'' and measurement of ``unfilled'' electronic surface states by the capacitance. They were devised to characterize reactive sorbed species. The detailed catalytic mechanism was based on studies of individual reaction steps under three solid‐state surface conditions: (1) only holes reacting, (2) only electrons reacting, and (3) both holes and electrons reacting. The first two correspond to the ZnO being an electroch...

209 citations