Room-Temperature Nitric Oxide Gas Sensors Based on NiO/SnO₂ Heterostructures

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Nitric oxide (NO) is a significant indoor air pollutant and a contributor to acid rain.
• Effective room-temperature NO sensors are in high demand for environmental monitoring.
• Metal oxide-based heterostructures show promise for gas sensing applications.

Purpose of the Study:

• To synthesize and characterize NiO/SnO2 heterostructures for NO gas sensing at room temperature.
• To investigate the influence of synthesis parameters (pH) and post-synthesis treatment (thermal annealing) on sensor performance.
• To evaluate the gas-sensing properties, including response, humidity effects, and stability.

Main Methods:

• NiO/SnO2 heterostructures were prepared using the polyol process.
• Structural and morphological analyses were performed using X-ray diffraction (XRD) and scanning electron microscopy (SEM).
• Energy-dispersive spectrometry (EDS) determined the NiO to SnO2 ratio. Gas sensing tests were conducted at room temperature with varying NO concentrations, pH, and annealing temperatures.

Main Results:

• The morphology of the NiO/SnO2 heterostructures was found to be rod-like, with size influenced by annealing temperature.
• Optimal sensor performance was achieved for heterostructures synthesized at pH = 8 and annealed at 900 °C.
• A response of 1.8% was observed for 2.5 ppm NO at room temperature under optimized conditions.

Conclusions:

• NiO/SnO2 heterostructures synthesized via the polyol process are effective for room-temperature NO detection.
• Synthesis pH and thermal annealing temperature are critical factors influencing the gas-sensing properties.
• The developed sensor demonstrates potential for environmental monitoring of nitric oxide pollution.