Surface microstructure-controlled ZrO2 for highly sensitive room-temperature NO2 sensors

Abstract The high sensitivity of room-temperature gas sensors is the key to innovation in the areas of environment, energy conservation and safety. However, metal-oxide-based sensors generally operate at high temperatures. Herein, we designed three ZrO2-based sensors and explored their NO2 sensing properties at room temperature. ZrO2 with three different morphologies and microstructure were synthesized by simple hydrothermal methods. The microstructures of sensing materials are expected to significantly affect gas sensing properties. The rod-shaped ZrO2 (ZrO2-R) displayed the advantages such as higher crystallinity, larger pore size, narrower band gap and more chemisorbed adsorbed oxygen, compared to hollow sphere-shaped ZrO2 (ZrO2-HS), stellate-shaped ZrO2 (ZrO2–S). The ZrO2-R sensor showed the highest response towards 30 ​ppm NO2 (423.8%) at room temperature, and a quite high sensitivity of 198.0% for detecting 5 ​ppm NO2. Although ZrO2-HS and ZrO2–S sensors exhibited lower response towards 30 ​ppm NO2 (232.9% and 245.1%), the response time and recovery time of these two sensors are 5 ​s/19 ​s and 4 ​s/3 ​s, respectively. This work can provide a new strategy for the development of room-temperature metal-oxide-based sensors.