NOVEL SOLAR ENERGY CONVERSION SYSTEM USING WATER AND SULFUR

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This year, we concentrated our research on the following topics aiming the accomplishment of solar energy conversion system (SECS)1.Development of highly efficient photocatalyst-This year, we succeeded in scaling up the photocatalyst synthesis process (developed last year) to obtain necessary quantity of CdS particles for efficient SECS. As a consequence, this year' s research was focused on the development of a photocatalytic cell that utilizes hydrogen sulfide (H_2S) dissolved in alkaline solution as raw material and separate the hydrogen evolved effectively.2.Removal of by-products evolved during reaction-When H_2S is photosplit, besides hydrogen, sulfur clusters (SC), which hinders the reaction is also produced as a by-product. Thus, a physical separation process based on electron transfer characteristics was developed to recover SC without degrading the reactants in the system. In this process, fullerene (C_<60>), which stably disperses in highly alkaline conditions, was used as a … More n electron donor. When fullerene was introduced into the yellow colored suspension dispersing SC, the suspension turned colorless instantaneously. Furthermore, sulfur (S) recovered by heat-treating sulfur-contained fullerene was used for the preparation of the raw material to produce H_2S.3.Reproduction of hydrogen sulfide from recovered sulfurThough circulation of sulfur was attempted by treating the same with water under hydrothermal conditions until last year, reproduction of H_2S using sulfate reducing bacteria (SRB) was attempted this year. As a result, we succeeded in the production of biogas containing 15 % of H_2S, which is equivalent to methane fermentation.4.Enrichment of hydrogen sulfideSince the H_2S produced by treating sulfur with SRB is associated with large quantities of methane and carbon dioxide, solid and liquid absorbents based enrichment technology was developed to obtain nearly 100 % H_2S.Solar energy conversion system was accomplished by carrying out the above researches. Less