Enhanced NO₂ gas-sensing performance of Pd/ZnO-codecorated SnO₂ nanorod sensors

SnO₂ nanorods codecorated with Pd and ZnO were synthesized using a three-step process involving: the synthesis of SnO₂ nanorods by the thermal evaporation of Sn powders followed by the sol–gel deposition of ZnO and Pd nanoparticles. The NO₂ gas-sensing properties of the nanorods were examined. The nanorods were composed of primitive tetragonal-structured single crystal SnO₂, while the ZnO and Pd nanoparticles were composed of wurtzite-structured ZnO single crystal and face-centered cubic-structured Pd single crystal, respectively. The Pd/ZnO-codecorated SnO₂ nanorod sensors showed a remarkably enhanced response to NO₂ compared to either ZnO or Pd-decorated SnO₂ nanorod sensors. The responses of multiple networked Pd/ZnO-decorated SnO₂ nanorod sensors were increased four to fivefold at NO₂ concentrations ranging from 1 to 5 ppm Pd/ZnO-decorated SnO₂ nanorod sensors which also showed shorter response and recovery times and higher selectivity than with ZnO or Pd-decorated SnO₂ nanorod sensors. The NO₂ sensing mechanism of the Pd/ZnO-codecorated SnO₂ nanorods is also discussed.