Thermochemical decomposition water splitting

High temperature (often exceeding 1000 K) drives the endothermic chemical reactions. Multistep cycles for water splitting are used because very high temperatures are required before an appreciable amount of water decomposes in single-step cycles. Thus, in one or more subsequent chemical reactions, the intermediary compounds can be recovered to the original substance, which is used repeatedly. The thermochemical water decomposition steps involve the following five principal reactions ... 

Roth, M., K.F. Knoche (1989), Thermochemical Water Splitting Through Direct HI Decomposition from H20-HI-I2 Solutions , Int.J. Hydrogen Energy, 14 (8), 545-549. 

Although H2S is at present a by-product of the desulfurization of fossil fuels on a large scale, only the recovery of free sulfur is carried out by the Claus treatment. On the other hand, the application of H2S decomposition as an H2 evolution method is proposed for use in the thermochemical process undertaken for water splitting. Thus, the thermochemical decomposition of H2S has wide-spread applications in various field. 

Hwang, G.J. and Onuki, K., Simulation study ou the catalytic decomposition of hydrogen iodide in a membrane reactor with a silica membrane for the thermochemical water splitting IS process. Journal of Membrane Science, 194, 207, 2001. 

Ginosar, D.M., Glenn, A.W., and Petkovic, L.M., Stability of Sulfuric Acid Decomposition Catalysts for Thermochemical Water Splitting Cycles, paper presented at the AlChE Spring Meeting 2005, Atlanta, 2005. 

In the thermochemical decomposition of water, chemical reactions, as well as heat, are used to split water into its components. One such system involves the following reactions (the temperature required for each is given in-parentheses) ... 

Decomposition of sulfuric acid presents an efficient means of generating oxygen via a solar thermochemical water splitting cycle pending the required reaction temperatures can be realizable. 

Because these temperatures are impractical, the thermochemical water-splitting cycles achieve the same result (i.e., separation of water into hydrogen and oxygen) at lower temperatures. A thermochemical water-splitting cycle is a series of chemical reactions tliat sum to the decomposition of water. To be useful, each reaction must be spontaneous and clean. Chemicals are chosen to create a closed loop where water can be fed to the process, oxygen and hydrogen gas are collected, and all other reactants are regenerated and recycled [2]. 

M. Roth and K.F. Knoche, Thermochemical water splitting through direct HI decomposition from H2O-HI 12 solutions , Int. J. Hydrogen Energy 14 545-9 (1989). 

In this study, the silica membranes to apply for HI decomposition reaction was investigated, and prepared by the sol-gel and the thermal chemical vapor deposition (CVD) methods. The objective of this work is to study the characteristics of the silica membrane preparation and the hydrogen permselectivity of the membrane reactor used for HI decomposition in the thermochemical water splitting IS process. 

This endothermic plasma-chemical process was considered, in particular, to be an important step in the thermochemical calcium-bromine-water splitting cycle for hydrogen production (Doctor, 2000). The plasma-chemical HBr decomposition (5-182) assumes in this case effective quenching and separation of products by fast rotation of quasi-thermal plasma... 

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