Low-Operating-Temperature NO₂ Sensor Based on a CeO₂/ZnO Heterojunction.

Area of Science:

• Materials Science
• Chemical Engineering
• Sensor Technology

Background:

• Chemiresistive sensors are crucial for gas detection.
• Low-operating-temperature sensors are desirable for energy efficiency and safety.
• Nitrogen dioxide (NO2) is a common air pollutant requiring sensitive detection methods.

Purpose of the Study:

• To develop and characterize CeO2/ZnO heterojunction nanorod-array based chemiresistive sensors.
• To evaluate their gas-detecting performance at low operating temperatures.
• To understand the mechanism behind enhanced gas sensitivity.

Main Methods:

• Synthesis of CeO2/ZnO heterojunction nanorod arrays via anodic electrodeposition coating and hydrothermal treatment.
• Fabrication of chemiresistive sensors using the synthesized nanorod arrays.
• Testing sensor response and selectivity to NO2 and interfering gases at various temperatures (120 °C and room temperature).

Main Results:

• The CeO2/ZnO heterojunction sensor exhibited significantly higher sensitivity to NO2 at 120 °C compared to pure ZnO.
• The sensor showed a linear and rapid response to NO2 even at room temperature (25 °C).
• Exceptional selectivity was observed, with a substantially lower response to interfering gases than to NO2.

Conclusions:

• The CeO2/ZnO heterojunction structure enhances gas-sensing performance at low temperatures.
• The built-in field at the heterojunction provides additional carriers for ZnO, improving adsorption.
• These findings highlight the potential of CeO2/ZnO heterojunctions for efficient low-temperature NO2 detection.