Hydrogen generation by irradiation of commercial CuO + TiO<inf>2</inf> mixtures at solar pilot plant scale and in presence of organic electron donors

© 2019 Elsevier B.V. A CuO + TiO2 mixture, based on two commercial and well characterized CuO and TiO2 photocatalyst, has been used to produce hydrogen by solar light irradiation and in presence of different organic compounds (methanol, glycerol, formic acid, and the components of a wastewater coming from the biodiesel industry) acting as sacrificial electron donors. The experiments have been conducted at Plataforma Solar de Almería (PSA, south of Spain) with a pilot plant scale reactor using a CPC (compound parabolic collector) configuration. The tested system has shown similar hydrogen generation capacity and energy efficiency than more expensive ones based on the use of noble metal/photocatalyst composites. Formic acid has shown to be the most effective electron donor, although very close amounts of hydrogen are also produced with glycerol, and this is found as a waste compound released in large quantities at the biodiesel industry wastewaters. As seen in previous similar studies, the increase of solution conductivity hampers the hydrogen generation, and a slightly basic solution pH (pH≈9) gives the best reaction conditions. Finally, the composite can be recovered and successfully reused giving the ensuing and sustained generation of H2 while removing more than 50% of TOC.