Surface modification of ZnO with WO₃ overlayer for enhanced hydrogen sensing

In this work, we report the hydrogen sensing properties of WO₃ modified ZnO film prepared by spray pyrolysis technique. The deposited films were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, photoluminescence spectroscopy and UV–vis spectroscopy. The effect of WO₃ additives on ZnO could be explained by the substitution of WO₃ into the ZnO lattice. The WO₃/ZnO film exhibits hexagonal wurtzite structure with (002) preferential growth orientation. The red shift in the PL peak suggests that the optical band gap of ZnO could be tuned by surface coating with WO₃. SEM micrographs revealed uniform dense particles morphology which changed to noodles like nano structure due to WO₃ activation. UV–vis-optical absorption revealed that the transmittance decreased with WO₃ layer, and band gap decreased from 3.34 to 3.29 eV. The overlayer of WO₃ on ZnO modified the particle size distribution, band gap, electrical conductivity, the catalytic activity, and thus, affected gas sensing property significantly. The H₂ sensing performance of the WO₃ layered ZnO was better than the pure ZnO.