ABSTRACT
Today, the major part of the energy consumed comes from chemical energy stored in fossil fuels. These fossil reserves are being rapidly depleted and the combustion has led to a severe pollution and disturbance of the environment. It is generally accepted that C0 2 (besides CH4, NOx and FCH) to a great extent contributes to the greenhouse effect. Due to the climate change, likely caused by the greenhouse effect, a growing interest has developed for new alternative energy sources not based on fossil fuel. Solar energy is a candidate of interest. Although solar energy has many advantages, it is an abundant resource and it is renewable, it is neither permanent nor constant in intensity over the world. Therefore, a suitable energy carrier for storage and transport is likely needed. Such an energy carrier could be dihydrogen. An energy system consisting of solar energy in combination with dihydrogen as an energy carrier would be an environmental friendly and attractive energy carrier for the future. Accordingly, the search of methods to produce dihydrogen using sunlight as energy source, for instance by direct photo-oxidation of water, has been a long-term research goal. In the quest for suitable semiconductor anode materials for direct photo-oxidation of water as well as for solar energy conversion, hematite (aFe203) has been a candidate of interest considering the following reasons:
(i) band gap of 2.0-2.3 eV [1-11]; (ii) chemical stability in aqueous solutions in a wide pH range [12, 13]; (iii) stability towards photocorrosion [12]; (iv) thermodynamic stable crystallo-graphic phase [14]. (v) thermal stability [15]; (vi) abundance of the material and low cost synthesis.
