Photocatalytic Hydrogen Production under Visible Light by Using a CdS/WO<inf>3</inf> Composite

© 2015 Springer Science+Business Media New York. Generation of H2 by visible irradiation of CdS/WO3 composite aqueous slurries in presence of sacrificial organic molecules has been studied. The composite was chosen by taking into account the advantageous position of conduction and valence band of both semiconductor and the fact that they can absorb visible light. A potential improvement of the photogenerated charge carrier separation has been tested by depositing onto the catalyst surface Pt and RuO2, the metal acting as electron sink and the oxide capturing the photogenerated holes. A tentative scheme of charge carrier transfer between the different composite phases is initially proposed but experimental data seems to invalidate such a hypothesis. A composite configuration based in the co-precipitation of CdS over a commercial WO3 followed by Pt deposition gave the best hydrogen productions, a production that is in the same order of magnitude of the efficiency of other photocatalysts previously tested in our laboratory. The characterization of the main properties of the catalysts seems to indicate that the improved generation of hydrogen found with the CdS/WO3 composite is directly related to the available surface area rather than being a consequence of the design of a favorable charge carrier circulation.