Self-assembled and Pd decorated Zn2SnO4/ZnO wire-sheet shape nano-heterostructures networks hydrogen gas sensors

Zn2SnO4/ZnO wire-sheet shape hetero-nanostructures (Zn2SnO4/ZnO HNS) networks gas sensors have been fabricated on Cr comb-shaped interdigitating electrodes with relatively narrower interspace of 1.5 µm using thermal evaporation of the mixed powders of ZnO, SnO2 and active carbon with Au catalysts. The self-assembly grown sensors of Zn2SnO4/ZnO HNS networks have excellent gas sensing characteristics to hydrogen concentration ranging from 2 to 1000 ppm at operating temperature of 120-300 °C. Comparing with Zn2SnO4/ZnO HNS networks sensors, the Pd decorated Zn2SnO4/ZnO HNS (Pd-Zn2SnO4/ZnO HNS) networks sensors exhibit enhanced hydrogen sensing performance such as higher response (74% at 255 °C to 1000 ppm H2), less response time (15 s at 270 °C to 1000 ppm H2), better selectivity (response to H2, C2H5OH, CH4, C2H2, CO, and C3H8), lower adsorption activation energy (12.72 kJ/mol to 1000 ppm H2) and smaller deviation from the ideal value of power exponent ß (0.49623 at 255 °C). The enhanced sensing properties of the Pd-Zn2SnO4/ZnO HNS can be ascribed to an additional depletion layer at the interface between Pd nanoparticles and Zn2SnO4/ZnO HNS. Both sensors show fine long-term stability during exposure to 2-1000 ppm H2 under relatively high operating temperature of 120-300 °C in 50 days.