Why Gas Sensors May Fail？

Gas sensors are crucial components in various applications, providing real-time information about the presence and concentration of gases. However, these sensors can face malfunction issues under certain conditions. This article explores three common reasons why gas sensors may fail and how solid-state polymer electrochemical sensors mitigate these challenges.

Impact of High-Concentration Gases:

Prolonged exposure to high-concentration gases, reaching levels of several thousand to hundreds of thousand parts per million (ppm), can lead to a significant overload of the sensor's catalytic electrode. This results in a powerful current overload that exceeds the sensor's designed overload range. Consequently, irreversible physical changes occur in the catalyst, causing a loss of catalytic efficiency and rendering the sensor unresponsive. Solid-state polymer electrochemical sensors, with electrodes completely enveloped in the electrolyte on the same two-dimensional plane, effectively address the current overload induced by high-concentration gas impact.

Soluble Gases Impact:

Gases that are highly soluble in water or solvents can adversely affect liquid-state electrochemical sensors when present in excessive concentrations. The internal structure of such sensors allows gases to flow through interconnected spaces. When high concentrations of gases enter the sensor and catalytic reactions cannot effectively occur within a short timeframe, excess gas can permeate the lower space of the sensor, reaching the electrolyte and altering its chemical properties. Solid-state polymer electrochemical sensors, featuring solid polymer electrolytes, effectively prevent the dissolution of high-concentration gas molecules that cannot be catalytically processed, thanks to their ability to impede gas diffusion through densely packed micropores.

Inability of Some Gas Molecules to Desorb:

The choice of catalyst in the sensor depends on the chemical characteristics of the measured gas. The catalyst may not have high catalytic efficiency for all gas molecules. For some strongly adsorptive gases, when the sensor cannot effectively catalyze their decomposition, these gas molecules continue to adsorb on the catalyst's surface. The higher the gas concentration, the more adsorption occurs. These molecules are challenging to desorb at room temperature, leading to accumulation. This accumulation results in a gradual reduction of the catalyst's catalytic efficiency for the target gas, forming irreversible sensitivity decline. Ultimately, the sensor becomes unresponsive, leading to "poisoning."

In summary, understanding the potential scenarios that can lead to the failing of gas sensors is crucial for developing effective strategies to mitigate these challenges and enhance the longevity and reliability of these sensing devices.