What is a hydrogen sensor? Working principle and classification introduction

Hydrogen, along with solar energy and nuclear energy, is known as the three major new energy sources because of its high combustion efficiency and pollution-free products. As a new energy source, hydrogen has been widely used in aviation, power and other fields. At the same time, as a reducing gas and carrier gas, hydrogen has extremely important application value in chemical industry, electronics, medical treatment, metal smelting, especially in the military and national defense fields. But hydrogen molecules are very small, in the process of production, storage, transportation and use is easy to leak, because hydrogen is not conducive to breathing, colorless and odorless, can not be found by the human nose, and the ignition point is only 585 ℃, the content of the air in the range of 4% ~ 75%, in case of open fire explosion Therefore, hydrogen sensors must be used in the use of hydrogen to detect the content of hydrogen in the environment and monitor its leakage.

Hydrogen sensor is very sensitive to hydrogen at room temperature and has good selectivity. It can be used as a sensor to detect hydrogen concentration in the environment. For safety requirements in production and life, fast, sensitive and accurate hydrogen sensor is very necessary to avoid the possibility of explosion in time.

I. Classification and principle of hydrogen sensor

1, semiconductor sensor

Take resistive semiconductor sensor as an example: mainly to sno2, zno,wo3 and other metal oxides as gas sensitive materials, for example: domestic qm series hydrogen sensor is to sno2 as hydrogen sensitive materials, so it is also called metal oxide semiconductor hydrogen sensor. Its working principle is as follows: after hydrogen is adsorbed, hydrogen, as the donor, releases electrons and combines with oxygen ions in the chemisorption layer. As a result, the carrier concentration changes, and the change value has a certain functional relationship with the volume fraction of hydrogen.

2, thermoelectric sensor

First, a layer of thermoelectric material is deposited on the substrate, and then a layer of catalytic metal, such as pt, pd, etc., is deposited on a part of the surface of the thermoelectric material. Finally, the catalytic metal layer and the thermoelectric film layer (no catalytic metal on the surface) are respectively used to extract the electrode, that is, the simplest thermoelectric hydrogen sensitive element is obtained. When the sensor is exposed to an environment containing hydrogen, hydrogen reacts with oxygen to generate water vapor and release heat under the action of catalytic metal. Therefore, the end with deposited catalytic metal has a high temperature, which is the hot end, while the end without catalytic metal has a low temperature, which is the cold end. The temperature difference between the hot end and the cold end is converted into the temperature difference potential, which is output by electrical signal, so as to realize the detection of hydrogen.

3. Optical fiber sensor

As a variety of solid-state hydrogen sensors use electrical signals, a common disadvantage is that they may generate electrical sparks, which poses a great safety hazard for the environment with a high volume fraction of hydrogen. Fiber optic sensors use optical signals, so they are suitable for explosive and dangerous environments.

4, palladium alloy film hydrogen sensor

The new third-generation hydrogen sensing technology is palladium alloy nano-thin film hydrogen sensing technology, which has real hydrogen specificity, 0~100% full range, no interference from other gases, no oxygen is required in the measurement process, and long service life.

2. Application scenarios of hydrogen sensor

1. Steel Mill

2. Battery system

3, transformer maintenance

4. Hydrogen alarm

5. Hydrogen exploration

Third, the development direction of hydrogen sensor

Problems such as selectivity, safety, stability, sensitivity and weak output signal of hydrogen sensor have been solved to varying degrees. To realize the normal temperature operation of hydrogen sensor, not only improve the safety of hydrogen sensor, but also reduce energy consumption, will be the focus of future research work. The hydrogen sensor can work at normal temperature in the following three ways:

1) Develop fiber optic hydrogen sensor, but it must solve the problems such as weak output signal, short service life and high cost;

2) The preparation of nano-scale hydrogen-sensitive materials, because the response of hydrogen-sensitive materials to hydrogen is fundamentally a kind of surface action, and nanomaterials have a large specific surface area, which increases the surface area of contact response. Moreover, the small particle size of nanomaterials reduces the response time and improves the response performance;

3) Actively develop new hydrogen sensitive materials.

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