Photosensitized reduction of carbon dioxide to methane and hydrogen evolution in the presence of ruthenium and osmium colloids: strategies to design selectivity of products distribution
| Autor: | Itamar Willner, Klaus Zengerle, Ruben Maidan, Daphna Mandler, Gisela Doerr, Heinz Duerr |
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| Rok vydání: | 1987 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 109:6080-6086 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja00254a029 |
| Popis: | Photoreduction of CO/sub 2/ to methane and higher hydrocarbons is accomplished in aqueous solutions by using visible light and Ru or Os colloids as catalysts. One system is composed of Ru(II) tris(bipyridine), Ru(bpy)/sub 3//sup 2 +/, as photosensitizer, triethanolamine, TEOA, as electron donor, and one of the following bipyridinium charge relays: N,N'-dimethyl-2,2'-bipyridinium, MQ/sup 2 +/ (1), N,N'-trimethylene-2,2'-bipyridinium, TQ/sup 2 +/ (2), N,N'-tetramethylene-2,2'-bipyridinium, DQ/sup 2 +/ (3), or N,N'-bis-(3-sulfonatopropyl)-3,3'-dimethyl-4,4'-bipyridinium, MPVS/sup 0/ (4). Illumination of these systems under CO/sub 2/ in the presence of Ru or Os colloids results in the formation of methane and ethylene and in H/sub 2/ evolution. In the second system, illumination of an aqueous solution under CO/sub 2/ that includes Ru(II) tris(bipyrazine) as sensitizer, TEOA as electron donor, and the Ru colloids leads to the formation of methane, ethylene, and ethane, and no H/sub 2/-evolution occurs. The reduction process of CO/sub 2/ proceeds via electron transfer of metal-activated CO/sub 2/ rather than through a hydrogenation route. Detailed studies show that the H/sub 2/-evolution process can be inhibited by the addition of bipyrazine, while CO/sub 2/ reduction is inhibited in the presence of added thiols. Methanation of CO/sub 2/ by hydrogen proceeds in the dark in the presencemore » of Pt and Ru or Os colloids and in the presence of MQ/sup 2 +/ (1). The need for the electron relay implies that the methanation process occurs through an electron-transfer mechanism.« less |
| Databáze: | OpenAIRE |
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