Moisture-Resistant and Highly Selective NH₃ Sensor Based on CdS/WS₂ Composite Heterojunction

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Developing highly sensitive and selective gas sensors for ammonia (NH₃) detection at room temperature is crucial for environmental monitoring and industrial safety.
• Existing gas sensing materials often face challenges with selectivity, response time, and stability under varying humidity conditions.
• Exploring novel composite materials with enhanced surface properties and heterojunction architectures is a promising approach to overcome these limitations.

Purpose of the Study:

• To synthesize and characterize CdS/WS₂ composites for room-temperature NH₃ gas sensing.
• To investigate the influence of the WS₂ to CdS mass ratio on the gas-sensitive properties of the composite.
• To evaluate the performance of the developed composite in terms of selectivity, response time, and stability against humidity interference.

Main Methods:

• Green and ultra-low-cost hydrothermal synthesis method was employed to create CdS/WS₂ composites.
• Systematic variation of the WS₂ and CdS mass ratio to optimize the heterostructure formation.
• Room-temperature gas sensing measurements were conducted to assess NH₃ detection performance, including selectivity, response/recovery times, and anti-humidity interference capabilities.

Main Results:

• An n-n type CdS/WS₂ heterostructure was successfully synthesized, exhibiting excellent NH₃ gas-sensitive properties at room temperature.
• The CdS/WS₂-40%wt composite demonstrated superior selectivity (over 4 orders of magnitude) for NH₃ sensing, a rapid recovery time of 3 seconds, and ultrahigh selectivity.
• The composite material showed remarkable stability under varying ambient humidity levels, indicating robustness for real-time monitoring applications.

Conclusions:

• The synthesized CdS/WS₂ composite offers a highly efficient and stable platform for room-temperature NH₃ gas sensing.
• The enhanced gas-sensing performance is attributed to the large specific surface area, 2D morphology, and the formation of a heterojunction between WS₂ and CdS.
• This research provides a foundation for designing next-generation, high-performance gas sensors operating under ambient conditions.