What are the knowledge points of electrochemical sensors?

The composition of electrochemical sensors

　　The electrochemical sensor contains the following 4 main components:

　　1. Breathable membrane (also called hydrophobic membrane): The breathable membrane is used to cover the sensing (catalytic) electrode, and in some cases it is used to control the molecular weight of the gas reaching the electrode surface. Such barriers are usually made of low-porosity Teflon films. This type of sensor is called a coated sensor. Alternatively, it can be covered with a high-porosity Teflon film, and the molecular weight of the gas reaching the electrode surface can be controlled with a capillary. This type of sensor is called a capillary sensor. In addition to providing mechanical protection for the sensor, the membrane also has the function of filtering out unwanted particles. In order to transmit the correct molecular weight of the gas, it is necessary to select the correct pore size of the membrane and capillary. The pore size should allow sufficient gas molecules to reach the sensing electrode. The pore size should also prevent liquid electrolyte leakage or rapid drying.

　　2. Electrode: The choice of electrode material is very important. The electrode material should be a catalytic material that can perform semi-electrolytic reactions over a long period of time. Generally, electrodes are made of precious metals, such as platinum or gold, which react effectively with gas molecules after catalysis. Depending on the design of the sensor, in order to complete the electrolysis reaction, the three electrodes can be made of different materials.

　　3. Electrolyte: The electrolyte must be able to carry out the electrolysis reaction and effectively transfer the ionic charge to the electrode. It must also form a stable reference potential with the reference electrode and be compatible with the materials used in the sensor. If the electrolyte evaporates too quickly, the sensor signal will weaken.

　　4. Filter: Sometimes a washing filter is installed in front of the sensor to filter out unwanted gas. The selection of filters is limited, and each filter has a different degree of efficiency. Most commonly used filter materials are activated carbon. Activated carbon can filter out most chemical substances, but not carbon monoxide. By choosing the right filter material, the electrochemical sensor can have higher selectivity for its target gas.

　　 3. Classification of electrochemical sensors

　　 There are many classification methods for electrochemical sensors, which can be divided into potential sensors, current sensors and conductivity sensors according to their output signals.

According to the different substances detected by electrochemical sensors, electrochemical sensors can be divided into ion sensors, gas sensors and biosensors.

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