H2 production by selective photo-dehydrogenation of ethanol in gas and liquid phase on CuOx/TiO2 nanocomposites

Abstract

CuOx/TiO2 nanocomposites prepared by copper photodeposition (1.0 and 2.5 wt% copper loading) on TiO2 (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. Cu2+ 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 H2 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 H2 and acetaldehyde has an economic value about 3.0–3.5 times higher than the alternative route of photoreforming to produce H2. Gas-phase operations would be preferable for the photo-dehydrogenation of ethanol

H2 production by photocatalytic reforming of oxygenated compounds using TiO2-based materials

“…Complete mineralization of ethanol takes place in a minor extent, considering the very low tendency of acetaldehyde to adsorb on the surface of the photocatalyst that therefore limits its subsequent degradation by reaction with holes. Notably, degradation of CH 3 CHO is hindered using less intense irradiation, as in the case of simulated sunlight [30,33], suggesting the possibility of selective dehydrogenation of ethanol leading to added-value byproducts [17,35].…”

Electrolyte-less design of PEC cells for solar fuels: Prospects and open issues in the development of cells and related catalytic electrodes

“…In addition, the photoanode should have a specific nanostructure coupling an effective light harvesting, to optimal charge separation and charge transport. This type of materials may be interesting not only as photoanode for EL-PEC solar cells, but also for other applications such as (i) direct ethanol fuel cells [102][103][104] and (ii) H 2 production by ethanol gas-phase photoreforming [105][106][107][108].…”

Cu–TiO2 systems for the photocatalytic H2 production: Influence of structural and surface support features

“…Traditionally, highly active photocatalysts are based on TiO 2 doped with noble metal ions (Pt, Au, Pd) acting as co-catalysts for charge trapping sites and avoid the electron-hole recombination processes [6][7][8][9][10]. Due to the high cost of such co-catalysts, transition metal doping with Cu, Fe, Co or Ni have recently turned as a promising option [11][12][13][14][15][16][17][18].…”