Feasibility of H2 sensors composed of tungsten oxide nanocluster films

The hydrogen (H₂) sensing properties, including the sensor response, response time and recovery time, of different sensor architectures based on tungsten oxide (WO₃) were investigated to assess the feasibility of using WO₃ in producing practical H₂ sensors. Each of the different sensor architectures consists of 3 layers. The first layer is a 2.5-nm palladium (Pd) layer, which is always deposited onto a highly porous WO₃ nanocluster layer. The third layer is an Au/Ti electrode layer, which may be constructed in the form of interdigitated electrodes or 5 × 5 mm² pad electrodes, which is located either on the top surface of the Pd layer or at the bottom of the WO₃ film. Furthermore, the WO₃ layer was also constructed to be either 11.2 nm or 153 nm thick. The sensor design consisting of a 2.5-nm Pd layer on an 11.2-nm WO₃ layer with interdigitated electrodes at the bottom of the layer was found to exhibit the best overall H₂ sensing properties, with excellent cyclic stability over 600 cycles of operation.