Hydrogen production for photocatalytic decomposition of water with urea as a reducing agent

Urea is expected to be used as a reducing agent in the photocatalytic formation of hydrogen from water because it is a non-petroleum material and abundant in domestic wastewater. In this study, a TiO2 catalyst co-doped with tantalum(V) and a trivalent metal cation, serving as promoters, was applied for the photocatalytic decomposition of water for hydrogen production using urea as the reducing agent. Co-doping of TiO2 with tantalum(V) and a trivalent metal cation resulted in a considerable redshift of the absorption edge of TiO2 via the formation of impurity levels. In particular, the incorporation of tantalum(V) and chromium(III) into TiO2 resulted in significant performance enhancement for the photocatalytic decomposition of water for hydrogen production. The products obtained from the photodecomposition of water with urea were also identified, and urea was transformed into N-2 and CO2 during the reaction. Moreover, the reaction was performed using thin-film photocatalysts based on organic semiconductors, such as picene, representing a class of novel, unconventional photocatalytic materials. Picene thin-films exhibited activity similar to that exhibited by traditional inorganic semiconductors. Effective utilisation of urea has potential application in a green and sustainable production of hydrogen from wastewater via photocatalysis using various semiconductors. (C) 2017 Elsevier B.V. All rights reserved.