Photocatalytic reforming of formic acid for hydrogen production in aqueous solutions containing cupric ions and TiO2 suspended nanoparticles under UV–simulated solar radiation

Hydrogen is the ideal candidate to fulfill the growing energy demand in a sustainable manner becauseof its high energy content and no emission of greenhouse gases from its combustion. Currently most ofhydrogen generation techniques involve the employment of fossil fuels, with consequent production oftoxic greenhouse gases. The possibility to produce hydrogen by means of photocatalytic processes usingthe solar radiation as energy source fits in perfectly with the switch to a more sustainable energy pro-duction. The solar photocatalytic hydrogen generation can be achieved by reforming organic substancescontained in civil or industrial wastewaters. This could allow to combine water decontamination withproduction of an energy carrier starting from a renewable source, the solar radiation.Within this perspective, a novel nano-TiO2photocatalytic system based on the solar reforming of formicacid in presence of cupric ions and chlorides has been investigated. The effect on hydrogen generationrate of the initial concentrations of formic acid, chloride and cupric ion, and pH values has been evaluated.For both formic acid and chloride ions, at least up to a starting concentration of 103mM, the higher theinitial concentration, the higher the rate of hydrogen generation. Hydrogen production has turned outto be noticeably dependent on cupric ion concentration. An almost opposite behavior has been foundvarying the starting cupric ion concentration in the range 2.5–20 mM, with the highest value of hydrogenproduction rate recorded for Cu(II) initial concentration equal to 5.0 mM. The pH value has been identifiedto be a crucial parameter of the system. A decrease in hydrogen production has been also observed risingpH of the solution from 1.0 to 4.0. A characterization of the solid samples recovered at the end of theruns has been performed by X-ray Diffractometry. These experimental outcomes have been rationalizedwithin a consistent reaction mechanism able to predict the system behavior under different operatingconditions. This work opens the way to the development of new competitive processes able to use wasteorganic streams for hydrogen generation through photacatalytic system based on solar energy.© 2015 Elsevier B.V. All rights reserved.