Microporous and Mesoporous Materials 22 ( 1998) 475–483 Synthesis and characterization of a ruthenium oxide–zeolite Y catalyst for photochemical oxidation of water to dioxygen1 Samar K. Das, Prabir K. Dutta * Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA Received 19 December 1997; received in revised form 24 March 1998; accepted 30 March 1998 Abstract In an integrated scheme for photochemical splitting of water to oxygen and hydrogen, there is a need for catalysts that couple the charge separated species to the redox reactions of water. Ruthenium oxide is well known as an efficient catalyst for photochemical four-electron oxidation of water to O 2 . Zeolites are an excellent host for creating long- lived photochemically generated charge-separated species. There is a need for mild methods of incorporation of catalysts onto zeolites for water oxidation reactions. We report here that thermal decomposition of RU 3 (CO) 12 on zeolite Y at 170°C produces Ru metal which is readily oxidized to RuO 2 by air. The morphology of RuO 2 on the zeolite is strongly dependent on the temperature at which air oxidation occurs. Samples of RuO 2 –zeolite made by air oxidation at 200°C produce fibers of RuO 2 of approximate dimensions of length of 50 nm and widths of 5 nm. This material is found to be an efficient catalyst for oxidation of water to oxygen by photochemically generated Ru(bpy)3+ 3 in solution. This study demonstrates that a specific morphology of RuO 2 is optimum for an effective catalyst, thereby suggesting that particular crystal faces of RuO 2 provide catalytic sites. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Artificial photosynthesis; Electron microscopy; Ruthenium carbonyl 1. Introduction energy often mimic natural photosynthesis, a pro- cess by which plants convert carbon dioxide and water to carbohydrates and oxygen using sunlight Over the past several decades, there has been [2]. Schematically photosynthesis can be repre- considerable interest in development of photo- sented as shown in Scheme 1. chemical systems that can efficiently convert water Attempts at mimicking photosynthesis have to oxygen and hydrogen using sunlight [1]. This shown considerable progress, though an efficient field of research is called artificial photosynthesis. functioning unit capable of converting water to Research strategies for photochemical use of solar O 2 and H 2 is yet to be realized [1]. There are several major obstacles that need to be overcome. * Corresponding author. Fax: +1 614 292 1685; Light absorption by a sensitizer initiates the redox E-mail: dutta.1@osu.edu process. Long-term charge separation which fol- 1Dedicated to Professor Lovat V.C. Rees in recognition and lows this light absorption is difficult to achieve appreciation of his lifelong devotion to zeolite science and his outstanding achievements in this field. because of efficient back electron transfer reac- 1387-1811/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved. PII: S1387-1811(98)00129-2