Solar energy and biowaste conversion into H2 on CuOx/TiO2 nanocomposites

The possibility to recover H2 from waste organic streams in biorefineries using photocatalytic approaches is an attractive option to enhance process sustainability and produce valuable energy products. With respect to the overall photoreforming to obtain H2 and CO2, the photo-dehydrogenation of bioethanol leads to the co-production of a valuable chemical (acetaldehyde) together with H2. Here we report on the synthesis and characterization of low cost CuOx/TiO2 nanocomposites and on their photocatalytic evaluation in the process of H2 production by selective photo-dehydrogenation of ethanol. The methods of sample preparation allowed to maximize the dispersion of copper nanoparticles on TiO2 surface, improving their photocatalytic performances in H2 production. CuOx/TiO2 materials were tested i) in liquid phase as a powder suspended in a typical slurry-type reactor and ii) in gas phase as a thin film using a novel reactor design. The aim of this contribution is to better understand analogies and differences between gas and liquid phase operations, which are important aspects to take into account in the reactor design. Results showed that gas phase operation allowed high H2 productivity and high selectivity (about 92-93 %) to acetaldehyde. It is remarked that the route of photo-dehydrogenation of ethanol to H2 and acetaldehyde has an economic value about 3.0-3.5 times higher than the alternative route of photoreforming to produce H2 and CO2.