Selective H₂ Gas Sensing Using ZIF-71/In-SnO₂ Bilayer Sensors: A Size-Selective Molecular Sieving Approach.

Area of Science:

• Materials Science
• Chemical Engineering
• Sensor Technology

Background:

• Selective gas sensing is crucial for environmental monitoring and industrial safety.
• Metal oxide sensors often suffer from cross-sensitivity to various gases.
• Microporous materials offer potential for size-selective gas filtration.

Purpose of the Study:

• To develop a universal method for creating selective hydrogen (H2) gas sensors.
• To integrate size-selective zeolitic imidazolate framework (ZIF) filter layers onto metal oxide sensing layers.
• To demonstrate enhanced H2 selectivity and reduced interference using ZIF filters.

Main Methods:

• Fabrication of a bilayer sensor consisting of indium-modified tin oxide (In-SnO2) and a ZIF filter layer.
• Formation of the ZIF layer via deposition of zinc oxide (ZnO) followed by in situ conversion to ZIF-8 or ZIF-71.
• Characterization using scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXRD), and N2 physisorption.

Main Results:

• A 57-nm-thick ZIF-71 filter layer significantly enhanced H2 sensor response at 180 °C.
• The ZIF-71 layer effectively suppressed interference from carbon monoxide (CO) via molecular sieving.
• The sensor demonstrated stable performance across a relative humidity range of 25-75%.

Conclusions:

• The integration of ZIF filter layers provides a universal strategy for selective H2 gas sensing.
• Rational design of microporous filter layers with defined pore apertures is key to achieving selective gas detection.
• This approach offers a promising pathway for developing advanced H2 sensors with improved performance.