Material Requirements of Gas Sensors: The Core Factor That Determines Performance Limits

In the field of gas detection, sensor structure, circuitry, and algorithms are undoubtedly important. However, what truly defines the performance boundaries is the functional material itself. Sensitivity, selectivity, stability, response speed, and service life can almost all be traced back to material-level choices.

From an engineering perspective, gas sensors do not simply “measure gas.” Instead, they utilize physical or chemical interactions between materials and gas molecules to convert invisible molecular behavior into measurable signals. Understanding material requirements is equivalent to understanding why different sensing technologies are suitable for different application scenarios.

I. General Core Requirements for Functional Materials in Gas Sensors

Despite differences in sensing principles, most gas sensors follow the same fundamental logic at the material level.

1. High Sensitivity: The Material Must Be Able to “Sense”

Sensitivity means that even at extremely low gas concentration changes, the material can still generate sufficiently noticeable electrical, optical, or frequency variations. This usually depends on:

• Strong interaction capability between the material surface and gas molecules

• A sufficiently large effective reaction interface

• Material properties favorable for signal amplification

If the material cannot effectively “capture” gas molecules, no amount of complex circuitry will help.

2. High Selectivity: Responding Only to the Target Gas

In real environments, target gases often coexist with various interfering gases. Materials must possess a certain “recognition capability,” making them more sensitive to target molecules while limiting responses to others.

This selectivity can be achieved through:

• Differences in catalytic activity

• Molecular size or diffusion rate screening

• Specific binding of surface functional groups

This is also one of the most challenging aspects of material science in gas sensing.

3. Stability and Reliability: Performance Must Not Degrade Rapidly

Engineering applications require sensors to operate long-term without frequent failure, imposing strict material requirements:

• Resistance to poisoning and contamination

• Low tendency toward sintering or structural collapse

• Low sensitivity to temperature and humidity variations

Material stability directly determines calibration intervals and service life.

4. Fast Response and Reversible Recovery

Ideal functional materials should generate signals rapidly upon gas exposure and recover quickly after gas removal. This requires good reversibility in adsorption, reaction, or mass transfer processes.

5. Reasonable Operating Temperature

Material activity is often highly temperature-dependent. Especially for sensors requiring heating, materials capable of operating at lower temperatures can significantly reduce power consumption and extend service life.

II. Material Priorities for Different Types of Gas Sensors

(1) Metal Oxide Semiconductor Gas Sensors

This is the most widely used sensor type, with performance highly dependent on the semiconductor material itself.

Core materials typically include N-type materials such as SnO₂, ZnO, In₂O₃, WO₃, as well as P-type materials like NiO and CuO.

Key material requirements include:

• High specific surface area, often in the form of nanoparticles, nanowires, or porous thin films

• Tunable catalytic activity, enhanced through noble metal or composite oxide doping

• High-temperature stability, maintaining structural integrity at 200–500 °C

In many cases, microstructure has a greater impact on performance than chemical composition.

(2) Electrochemical Gas Sensors

The performance of electrochemical sensors is jointly determined by the “electrode + electrolyte” system.

• Electrode materials commonly use noble metals such as Pt and Au

• Electrolytes may be liquid or solid polymer-based

Key material considerations include:

• Selectivity of catalytic reactions

• Long-term stability of the electrolyte

• Barrier performance of sealing materials against moisture and impurities

Electrochemical sensors do not pursue high-temperature activity but emphasize controllable chemical reaction pathways.

(3) Catalytic Combustion Gas Sensors

Catalytic combustion sensors are mainly used for combustible gas detection, with the core being the “catalytic bead” structure.

Material requirements focus on:

• The ability of the catalyst to trigger flameless combustion at low temperatures

• Resistance to poisoning by sulfur, silicon, and similar substances

• Mechanical strength and thermal stability of the carrier material

Degradation of catalytic performance often directly determines sensor lifespan.

(4) Optical Gas Sensors (NDIR, etc.)

Material requirements for optical sensors mainly involve optical consistency and stability.

Key materials include:

• Infrared light sources at specific wavelengths

• High-reflectivity optical cavity materials

• Infrared detectors and interference filters

The core requirement is not “reactivity” but long-term stability of spectral characteristics.

(5) Surface Acoustic Wave (SAW) Gas Sensors

The sensitivity of SAW sensors is highly dependent on sensitive thin-film materials.

• Piezoelectric substrates must exhibit excellent frequency stability

• Thin films must selectively adsorb target gases

Film uniformity and reversible adsorption capability are critical selection criteria.

(6) Chemiresistive Sensors Based on Emerging Functional Materials

Graphene, carbon nanotubes, conductive polymers, and MOFs provide new pathways for room-temperature, high-sensitivity detection.

Material advantages include:

• High surface modifiability

• Molecular-level recognition potential

• Low-power or even heater-free operation

Engineering challenges mainly lie in stability and consistency control.

III. Impact of Material Selection on Engineering Applications

From an engineering standpoint, material selection determines not only whether detection is possible, but also:

• Suitability for continuous online monitoring

• Compatibility with battery-powered systems

• Consistency in large-scale mass production

This is why the optimal sensing technology differs across application scenarios.

IV. Nexisense’s Engineering Approach to Material Selection

In gas sensing applications, Nexisense places greater emphasis on:

• Long-term stability and repeatability

• Adaptability to complex environments

• Compatibility with system-level design

Materials are not isolated indicators but the foundation of overall system reliability.

V. Frequently Asked Questions (10)

1. Why do gas sensors drift easily?
   Mostly due to material aging or poisoning.

2. Are nanomaterials always better?
   They offer higher sensitivity, but stability must be balanced.

3. Are MOF materials suitable for industrial applications?
   They are still in the gradual engineering stage.

4. Why do metal oxide sensors require high temperatures?
   To activate surface chemical reactions.

5. Are optical sensors completely drift-free?
   Drift is relatively low but still requires optical stability design.

6. What determines the lifespan of electrochemical sensors?
   Mainly the electrolyte and electrode materials.

7. Why do catalytic combustion sensors become poisoned?
   Active catalytic sites are covered or destroyed.

8. Can new materials replace traditional solutions?
   They already show potential in some applications.

9. Does material selection affect response time?
   It directly affects gas diffusion and reaction rates.

10. Can users replace functional materials themselves?
    Generally not feasible in engineering practice.

VI. Conclusion

The materials used in gas sensors are not simple “carriers” but the core of the entire detection mechanism. Behind different sensing principles lies the fundamental difference in how materials interact with gas molecules.

With advances in nanotechnology, composite materials, and emerging functional materials, gas sensors are evolving toward higher sensitivity, stronger selectivity, and lower power consumption. However, regardless of technological evolution, material selection remains the first-principle factor determining performance limits.