Temperature-Dependent NO₂ Sensing Mechanisms over Indium Oxide.

Area of Science:

• Materials Science
• Surface Chemistry
• Chemical Sensing

Background:

• Indium oxide (In₂O₃) is a promising material for gas sensing applications.
• Understanding the surface mechanisms is crucial for optimizing sensor performance.

Purpose of the Study:

• To investigate the surface species involved in nitrogen dioxide (NO₂) gas sensing on indium oxide.
• To elucidate the role of surface reactions in the temperature-dependent sensing mechanism.

Main Methods:

• Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) was employed.
• Multivariate spectral analysis was coupled with DRIFTS for detailed surface species identification.

Main Results:

• Surface nitrites were identified as crucial intermediates in the NO₂ sensing mechanism.
• The interaction between surface nitrites and hydroxyl groups significantly influences sensing.
• A highly hydroxylated surface enhances NO₂ adsorption, improving sensor response at lower temperatures.

Conclusions:

• Surface nitrites play a vital role in the temperature-dependent NO₂ gas sensing mechanism of indium oxide.
• Optimizing surface hydroxylation and water adsorption is key to enhancing sensor sensitivity at reduced operating temperatures.