Photocatalytic production of hydrogen: An innovative use for biomass derivatives

Abstract

Hydrogen is considered the energy carrier of the future because of its clean and very flexible conversion into different forms of energy, e.g., into heat via combustion or electricity via fuel cells. Traditionally, hydrogen is produced form natural gas steam reforming form fossil fuels making the effective implementation of hydrogen economically and environmentally unsustainable. To overcome this problem, several routes are being proposed for hydrogen production form renewable sources. Recent research points to the photoinduced reforming of biomass as a promising possibility, since it uses solar radiation, an inexhaustible source of energy, and raw materials derived form renewable sources such as biomass and water. Studies in this field are still incipient but quite encouraging. The process combines photocatalytic water splitting with the photodecomposition of organic compounds mediated by an irradiated semiconductor. In this process, the water oxidation reaction is suppressed by a sacrificial electron donor (biomass), as well as the formation of superoxide radicals when the reaction is carried out under anaerobic conditions. The hydrogen production rates form photoinduced reforming are similar or superior to other processes, including biomass hydrolysis and aqueous phase reforming. However, the major researches into hydrogen production by photoinduced reforming of biomass derivatives have focused on TiO2, which limits the portion of solar radiation absorbed as UV light. Thus, the current challenge in this field is the development of narrow band gap semiconductors that are able to drive the photoinduced reform of biomass with visible light, which corresponds to about 43% of solar radiation. © 2011 Sociedade Brasileira de Química.