H 2 production by selective photo-dehydrogenation of ethanol in gas and liquid phase on CuO x /TiO 2 nanocomposites Claudio Ampelli, * a Rosalba Passalacqua, a Chiara Genovese, a Siglinda Perathoner, a Gabriele Centi, a Tiziano Montini, b Valentina Gombac, b Juan Jos´ e Delgado Jaen c and Paolo Fornasiero b CuO x /TiO 2 nanocomposites prepared by copper photodeposition (1.0 and 2.5 wt% copper loading) on TiO 2 (synthesized by three different routes) are studied in the ethanol photo-dehydrogenation in gas- and liquid-phase operations, and characterized in terms of surface area, phase composition by XRD, morphology and copper-oxide nanoparticle size distribution, and copper species by UV-visible diffuse reflectance spectroscopy. Cu 2+ ions partially enter into the titania structure leading to the creation of oxygen vacancies responsible for the shift in the band gap, but also the creation of traps for photogenerated holes and electrons. While the band gap shifts to lower energies with the copper content, a maximum photocatalytic activity is shown for the intermediate copper loading. Gas-phase operations allow a higher H 2 productivity with respect to liquid-phase operations, and especially a higher selectivity (about 92–93%) to acetaldehyde. It is remarked that the route of photo- dehydrogenation of ethanol to H 2 and acetaldehyde has an economic value about 3.0–3.5 times higher than the alternative route of photoreforming to produce H 2 . Gas-phase operations would be preferable for the photo-dehydrogenation of ethanol. 1. Introduction The possibility to recover H 2 from waste organic streams in bioreneries using photocatalytic approaches is an attractive option to enhance process sustainability and produce valuable energy products. 1 Various authors have investigated the pho- tocatalytic reforming of biomass-derived products (biowaste) as a promising way to produce hydrogen using renewable energy. 2,3 Ma et al. 4 have investigated the photocatalytic reforming of methanol on Pt/TiO 2 –SO 4 2 as a model reaction of biomass reforming. Colmenares et al. 5 have studied Pt/TiO 2 and Pd/TiO 2 for photocatalytic reforming of glucose water solutions. Gu et al. 6 have analyzed the photocatalytic reforming of 2-propanol over Pt/TiO 2 photocatalyst. Xu et al. 7 have explored the photo- catalytic hydrogen production by reforming of biomass by- products (methanol, glycerol and glucose) using different Pt/TiO 2 photocatalysts with variable ratio of the anatase–rutile titania phases. The same research group has also investigated the H 2 production via photocatalytic reforming of methanol on Au/TiO 2 catalyst 8 and the role of surface modication of titania by anion adsorption to control the selectivity in H 2 formation. 9 De Oliveira Melo and Silva 10 have used Pt/CdS/TiO 2 hybrid photocatalysts for the photoreforming of glycerol. Daskalaki and Kondarides 11 have analyzed the photocatalytic reforming of aqueous solutions of glycerol using a Pt/TiO 2 photocatalyst. Bowker et al. 12 have also investigated the photocatalytic reforming of glycerol to H 2 over Pd- and Au-modied TiO 2 catalysts. An intense research activity on this topic was thus made in recent years, but mainly focused on the use of titania modied with noble metals and the reaction of photoreforming of biomass byproducts, e.g. with conversion of the organic to CO 2 . With few exceptions, 13 the reaction was studied using the pho- tocatalyst in the form of a solid dispersed in the liquid phase (an aqueous solution containing the biomass-derived products). From the practical perspective it would be preferable the use of a thin lm of the solid catalyst (avoids the problems related to separation, leaching, etc.) in contact with a gaseous stream containing the biowaste, because (i) many unused gaseous waste streams are present in biorenery, (ii) it is avoided light scattering due to the liquid (thus better potential efficiencies in light use) and (iii) product recovery is easier and less costly. In addition, avoiding the use of noble metals is an important a Dipartimento di Ingegneria Elettronica, Chimica e Ingegneria Industriale, Universit` a degli Studi di Messina e INSTM/CASPE (Laboratory of Catalysis for Sustainable Production and Energy), viale F. Stagno d'Alcontres 31, 98166 Messina, Italy. E-mail: ampellic@unime.it b Dipartimento di Scienze Chimiche e Farmaceutiche, Universit` a degli Studi di Trieste, ICCOM-CNR e INSTM, via L. Giorgieri 1, 34127 Trieste, Italy c Departamento de Ciencia de los Materiales e Ingenier´ ıa Metal´ urgica y Qu´ ımica Inorg´ anica, Facultad de Ciencias, Universidade de Cadiz, Campus Rio San Pedro, Puerto Real, 11510, Cadiz, Spain Cite this: RSC Adv., 2013, 3, 21776 Received 7th November 2012 Accepted 6th September 2013 DOI: 10.1039/c3ra22804e www.rsc.org/advances 21776 | RSC Adv., 2013, 3, 21776–21788 This journal is ª The Royal Society of Chemistry 2013 RSC Advances PAPER Published on 09 September 2013. Downloaded by Universita di Messina on 21/02/2014 10:45:20. View Article Online View Journal | View Issue