Hydrothermal synthesis of hierarchically porous Rh-doped ZnO and its high gas sensing performance to acetone

The hierarchically porous Rh-doped ZnO and pure ZnO samples have been successfully synthesized through a simple hydrothermal reaction process at 180 °C. The morphology and composition were carefully characterized by X-ray diffraction, field emission scanning electronic microscopy, transmission electron microscopy and BET. Gas-sensing testing results demonstrated that ZnO doped with 1 mol% Rh significantly improve gas sensitivity from pure ZnO. The high sensitivity of the sensor based on 1 mol% Rh doping ZnO was of 142–100 ppm acetone, the response increased linearly with the concentration of acetone in the range of 50–1500 ppm. All the response and recovery times of the sensors were less than 20 s at a low working temperature of 340 °C. The improved response of Rh-doped ZnO sensor was related to the electronic interaction of Rh₂O₃ and ZnO due to heterojunction formation. The good sensing performances of the Rh-doped ZnO sensor indicated that hierarchically porous Rh-doped ZnO could be a promising candidate for highly sensitive gas sensors.