Visible light photocatalytic hydrogen generation using dye-sensitized graphene oxide as photocatalyst

Visible light photocatalytic hydrogen generation using dye-sensitized graphene oxide as photocatalyst C. Lavorato(1,2)*, M. Latorre-Sánchez (1), M. Puche(1) V. Fornés (1), R. Molinari (2) and H. Garcia(1) (1) Instituto Universitario de Tecnología Química, Univ. Politecnica de Valencia, Av. De los Naranjos s/n, 46022 Valencia, Spain (2) Department of Chemical and Materials Engineering, University of Calabria, Via P. Bucci 44/A, I87036 Rende, CS Italy * E-mail: lavorato.cristina@libero.it Dye sensitized graphene oxide is able to generate hydrogen from water/methanol (80/20 %v/v) mixtures using visible or solar light. Two GO materials obtained by different chemical oxidation of graphite have been tested to generate hydrogen under visible light. This preliminary study indicate that the less oxidized GO sample (GO1) was more efficient than the GO sample with higher oxygen content (GO2). Combination of less oxidized Graphene oxide with a series of dyes under 532nm have been studied to increase the efficiency. The most efficient photocatalyst tested (quantum yield 6% at 532 nm) contained tris(2,2’-bipyridyl)ruthenium(II) complex incorporated in the interlayer spaces of a few-layers graphene oxide increasing the amount of hydrogen production by a factor of 14 with respect to the plane GO. This new material was obtained by refluxing the ruthenium complex and the oxidized graphite leading to a cationic exchange of the complex. Incorporation of the [Ru(bipy)3]2+ complex between the oxidized graphite layers was assessed by X-ray diffraction (XRD) that shows a shift in the position of the diffraction peak from 2θ 11.5 o corresponding to oxidized graphite1 to smaller 2θ angle (6 o) that according to the Bragg diffraction law corresponds to a interlamellar distance of 14.09 Å. The photocatalytic system is not stable for longer irradiation time by using 532nm laser irradiation due to dyes degradation upon extensive use. References [1] D. C. Marcano, D. V. Kosynkin, J. M. Berlin, A. Sinitskii, Z. Sun, A. Slesarev, L. B. Alemany, W. Lu, J. M. Tour. ACS Nano. 4, 4806-4814 (2010).