Hydrogen photolytic from water

Note 2 More efficient methods than electrolysis for obtaining hydrogen from water are under investigation. One of these is thermochemical decomposition. Another is photochemical decomposition by solar radiation, either directly or via a solar power generator. Photolytic decomposition of water with platinum catalyst has been achieved. Hydrogen can also be obtained by photolytic decomposition of hydrogen sulfide with cadmium sulfide catalyst. 

Figure 1, The platinized Chi a cell. The Chi a-free electrode is used as a half cell in a liquid-junction photovoltaic cell. In photolytic reaction, only the platinized Chi a electrode is used in the production of molecular hydrogen and oxygen from water.

Photolytic. Methyl formate, formed from the irradiation of dimethyl ether in the presence of chlorine, degraded to carbon dioxide, water, and small amounts of formic acid. Continued irradiation degraded formic acid to carbon dioxide, water, and hydrogen chloride (Kallos and Tou, 1977 Good et al, 1999). 

Photolytic Ozonation has been known for over a decade as a powerful water treatment process for the destruction of organic compounds, but its mode of action has not been understood. It is shown using kinetic arguments and data from scavenging experiments that photolysis of aqueous ozone yields hydrogen peroxide, which then reacts with further ozone in a complex series of reactions to yield hydroxyl radical. The proposed mechanism is shown to explain pH behavior of model compound destruction in earlier data. 

In the present study, the mechanism of photolytic ozonation was investigated in the laboratory by measuring ozone, hydrogen peroxide, and total oxidant levels in purified water as a function of time in a two-liter stirred tank reactor in which concurrent ozone sparging and UV irradiation were taking place. Experiments were run in the presence and absence of various radical scavengers and the results Interpreted in terms of reaction rate constants taken from the literature. This paper will discuss the mechanism of photolytic ozonation, show its relationship to other ozonation processes, and... 

In addition to the photolytic ozonation experiments described above, hydrogen peroxide photolysis experiments were performed in the presence and absence of hydroxyl radical scavengers. These experiments were run using distilled water (a) as it came from the lab reservoir, (b) after oxygenation, and (c) after sparging with nitrogen to remove oxygen. The results are shown in Table I, in the form of the observed rate constants. 

The true nature of oxidative phosphorylation, i.e. the synthesis of ATP linked to the transfer of electrons along a chain of electron (or hydrogen) carriers, was emphasized by the discovery of photosynthetic phosphorylation in chloroplasts by Arnon in 1954.< > Here neither oxidizable substrates nor oxygen play a role. Electrons derived from the photolytic cleavage of water are fed into an electron-transfer chain and withdrawn at the other end of the chain by the oxidizing equivalents formed by the photolytic reaction. 

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