Fe2O3/CdS co-sensitized titania nanotube for hydrogen generation from photocatalytic splitting water

CdS, Fe2O3-sensitized and Fe2O3/CdS co-sensitized TiO2 nanotube arrays (TNA) were fabricated by depositing CdS and Fe2O3 nanoparticles onto the surface of TNA via an ultrasonic-assisted chemical bath deposition (CBD) method. Their effects on the photocatalytic properties and hydrogen generation rate were evaluated. The results show that CdS-sensitized and Fe2O3/CdS co-sensitized TNA have good absorption on long wavelength region and exhibit much higher hydrogen generation rates than those of other TNA specimens. The hydrogen generation rates for TNA-Fe2O3/CdS and TNA-CdS/Fe2O3 were 12 and 1.54 ml cm−2 h−1, respectively, where the TNA-Fe2O3/CdS refers to the deposition of Fe2O3 first on TNA and CdS the second, CdS being the out surface materials and contacting water. TNA-CdS/Fe2O3 is a reversed structure of TNA-Fe2O3/CdS. The rate of hydrogen generation for TNA-Fe2O3/CdS was five times higher than that of blank TNA (2.43 ml⋅cm−2 h−1). It is considered that the low efficiency of TNA-CdS/Fe2O3 is due to a disadvantageous energy band structure for electrons and holes transition. TNA-Fe2O3/CdS has a stepwise energy band structure and the transition of excited electrons and holes is straightforward, while those of TNA-CdS/Fe2O3 has a difficult transition process due to a reverse structure.