A catalytic semiconductor dual-mode hydrogen sensor

Abstract

The present invention provides a catalytic semiconductor dual-mode hydrogen sensor, the overall structure of which is a Wheatstone bridge structure, and the hydrogen concentration is determined by the voltage difference between two series elements in each of two parallel branches; on this basis, the semiconductor material is connected in parallel with a catalytic combustion resistor. The purpose of the present invention is to provide a hydrogen sensor that can achieve high-precision detection of any concentration within a large concentration variation range; that is, a hydrogen sensor for high precision (<10ppm), a response time of less than 1s, and a detectable concentration range of 10-40000ppm (0.001%-4%).

Description

Technical Field

[0001] The invention belongs to the field of gas sensors, and specifically relates to a hydrogen sensor, and in particular to a catalytic semiconductor dual-mode hydrogen sensor. Background Art

[0002] Energy is an important support for the development of national economy. The modernization of world economy benefits from non-renewable energy such as oil, natural gas and coal. However, the excessive use of these energy will eventually lead to their exhaustion. A cleaner and renewable new energy is becoming increasingly important. Hydrogen is the lightest chemical element and the smallest molecule. Due to its low density and high diffusion rate, hydrogen diffuses much faster in the air than gasoline. Once hydrogen leaks, it will spread rapidly. The high dispersion makes hydrogen more difficult to control than other gases. Therefore, a major technical challenge of hydrogen fuel is its transportation and storage.

[0003] Hydrogen has a large flammable range of 4%-75%. How to scientifically and effectively detect hydrogen concentration and reduce or prevent engineering problems such as hydrogen explosions is particularly important. From a technical perspective, hydrogen sensors can effectively detect hydrogen concentrations. Once there is a hydrogen leak, the sensor can quickly capture and detect hydrogen.

[0004] Hydrogen sensors can be divided into electrochemical, optical, and resistive types according to their working principles. The principles of the current mainstream hydrogen sensors are mainly catalytic combustion and semiconductor.

[0005] The catalytic combustion sensor is composed of a sensitive element and a compensating element. The sensitive element and the sensitive body contain catalysts, while the sensitive body of the compensating element does not contain catalysts. It is used to compensate for the impact of changes in ambient temperature and humidity on the output of the hydrogen sensor. When the catalytic combustion hydrogen sensor is working, the platinum wire of the hydrogen sensor itself generates heat under the condition of an applied voltage, causing the temperature of the sensitive body to reach about 200-300°C. At this temperature, when the hydrogen exceeds 1000ppm, it will come into contact with oxygen in the air under the action of the catalyst to undergo an oxidation reaction, generating reaction heat, which will increase the temperature of the platinum wire used as the heating wire and increase the resistance value accordingly. In general, the volume fraction of hydrogen in the atmosphere to be measured is not too high, less than 4%, and hydrogen can be completely burned. Its calorific value is related to the hydrogen concentration. The greater the volume fraction of hydrogen gas in the atmosphere to be measured, the greater the reaction heat, the greater the temperature increase of the platinum wire, and the greater the increase in its resistance. Therefore, as long as the resistance change value (ΔR) of the platinum wire is measured, the hydrogen concentration can be detected, C H =f(ΔR),C H is the hydrogen concentration, and each ΔR corresponds to a concentration value. However, since a certain concentration is required to make air burn, and the concentration limit is 1000ppm, the catalytic combustion gas sensor will not work below 1000ppm.

[0006] Semiconductor hydrogen sensors are composed of hydrogen-sensitive materials such as precious metal catalysts and metal oxides. They are surface-sensitive sensors that do not generate high temperatures like catalytic combustion. After hydrogen contacts the material, the conductivity of the semiconductor material changes, thereby achieving hydrogen measurement. Although semiconductor sensors have high measurement accuracy, they have low stability and are greatly affected by the environment. In addition, semiconductor sensors have sensor drift, so their application still has certain limitations.

[0007] The Wheatstone bridge structure determines the hydrogen concentration by the voltage difference between the two series elements in each branch of the two parallel branches. The principle is: in the air state, Figure 1 For example, the voltage at the node between two series elements in two parallel branches can be expressed as When R 11 =R 13 , R 12 =R 14 When V 0 = 0. Component 13 reacts with hydrogen and causes resistance R 13 When the R 11 ≠R 13 , resulting in V 0 ≠0, hydrogen concentration and voltage V 0 A corresponding relationship can be established between them to determine the hydrogen concentration, and the establishment of this relationship is mainly implemented in the control panel. Summary of the invention

[0008] The object of the present invention is to provide a hydrogen sensor which can achieve high-precision detection of any concentration within a relatively large concentration variation range.

[0009] A catalytic semiconductor dual-mode hydrogen sensor has an overall structure of a Wheatstone bridge structure. The hydrogen concentration is determined by the voltage difference between two series elements in each of two parallel branches. On this basis, the semiconductor material is connected in parallel with a catalytic combustion resistor.

[0010] A catalytic semiconductor dual-mode hydrogen sensor, the overall structure of which is a Wheatstone bridge structure, including two parallel branches;

[0011] The series elements of one parallel branch are composed of reference resistor A11 and reference resistor B12;

[0012] The series elements of another parallel branch are composed of a parallel structure 13 and a catalytic combustion module A14 , and the parallel structure 13 is composed of a catalytic combustion module B7 a and a semiconductor module 8 .

[0013] Furthermore, the reference resistor 11 and the parallel structure 13 have the same resistance value at room temperature and pressure, and the reference resistor 12 and the catalytic combustion module 14A have the same resistance value at room temperature and pressure.

[0014] Furthermore, the material of the semiconductor module 8 is In doped with transition elements. 2 O 3 or SnO 2 .

[0015] Furthermore, the transition elements doped in the semiconductor module 8 include Pb, Rh, Ru, Y, Zr, Nb, Mo, Tc, Cd, Ir, Os, Ta, Hf, lanthanides and actinides; the doping concentration is 0.01%-3%; the material of the semiconductor module 8 is preferably In doped with 0.05% Pb. 2 O 3 .

[0016] Furthermore, the catalytic combustion module B7a and the semiconductor module 8 are coated with a catalytic gas sensitive layer Pt catalyst.

[0017] Furthermore, the shapes of the catalytic combustion module B7a and the catalytic combustion module A14 include a straight line with a width of 0.01 cm-5 cm; the surface area can be changed accordingly.

[0018] Furthermore, the shape of the material of the semiconductor module 8 includes a straight line, a width of 0.01 cm-2 cm, and a surface area that is variable accordingly.

[0019] Furthermore, a catalytic semiconductor dual-mode hydrogen sensor also includes: a heating electrode 2, a ceramic substrate 5, a thermal insulation layer 4, a silicon base 6, and a conductive material 9.

[0020] Furthermore, the conductive material 9 is one of Pt, Au, Ag, Cu, Al, Ni, W, Ag / Pd alloy, or Pt / Au alloy.

[0021] Technical effects of the present invention:

[0022] (1) The hydrogen sensor of the present invention can be used for hydrogen detection with high accuracy (<10 ppm), a response time of less than 1 s, and a detectable concentration range of 10-40000 ppm (0.001%-4%).

[0023] (2) The hydrogen sensor of the present invention adopts a three-dimensional structure design, which is smaller in size than other types of sensors and can meet the needs of applications in various small spaces, including the interior of a car or complex machinery with a small and complex space.

[0024] (3) The hydrogen sensor of the present invention adopts a dual-mode structure. The semiconductor and catalytic combustion principles overlap in the working concentration of the detected gas. Compared with single-principle gas sensors, the stability and accuracy are higher and the life is longer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings generally illustrate various embodiments by way of example and not limitation, and together with the description and claims, serve to illustrate the embodiments of the invention. Where appropriate, the same reference numerals are used throughout the drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the present apparatus or method.

[0026] Figure 1 A simplified schematic diagram of the structure of the present invention is shown;

[0027] Figure 2 A side view showing the structure of the present invention;

[0028] Figure 3 A top view of the structure of the present invention is shown;

[0029] Figure 4 A schematic diagram of the circuit structure of a specific embodiment 1 of the present invention is shown;

[0030] Figure 5 A schematic diagram of the circuit structure of a specific embodiment 2 of the present invention is shown;

[0031] Figure 6 A schematic diagram of the circuit structure of a specific embodiment 3 of the present invention is shown;

[0032] Figure 7 A circuit structure diagram of a specific embodiment 4 of the present invention is shown.

[0033] Reference numerals:

[0034] 11- Reference resistance A,

[0035] 12- Reference resistor B,

[0036] 13-Parallel structure,

[0037] 14- Catalytic combustion module A,

[0038] 7a- Catalytic combustion module B,

[0039] 8- Semiconductor module,

[0040] 2- Heating electrode,

[0041] 4- Thermal insulation layer,

[0042] 5- Ceramic substrate,

[0043] 6-Silicon-based,

[0044] 9- Conductive materials. DETAILED DESCRIPTION

[0045] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments. Specific embodiment 1

[0047] like Figure 4 As shown, in the parallel structure 13, there is only the catalytic combustion module B7a coated with Pt catalyst, and the semiconductor module 8 is not connected in parallel with the catalytic combustion module B7a. Instead, the semiconductor module 8 is connected in parallel with the catalytic combustion module A14 which is not coated with catalyst. When the catalytic combustion module is working, the temperature of the semiconductor module 8 can be reduced, and the temperature interference caused by the catalytic combustion module to the semiconductor module can be reduced, thereby increasing the stability of the sensor. Specific embodiment 2

[0049] like Figure 5 As shown, Figure 1 The reference resistors A11 and B12 are not placed inside the sensitive layer, but outside the sensitive layer. Since the reference resistors A11 and B12 are reference resistors and do not react with the gas, their positions do not need to be fixed inside the sensitive layer, so they can also be placed outside, thereby reducing the volume of the sensitive layer. Specific embodiment 3

[0051] like Figure 6 As shown, Figure 4 The heating electrode 2 in the sensor penetrates the heat-insulating layer 4. The startup speed of the sensor is increased, the startup time is reduced, and since the heating electrode 2 is not in direct contact with the reference resistor, the reference element is less affected. Specific embodiment 4

[0053] like Figure 7 As shown, Figure 2 The reference resistors A11 and B12 do not penetrate the ceramic substrate, which further reduces the influence of the heating electrode 2 on the reference resistors, thereby increasing the accuracy of the measurement.

[0054] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A catalytic semiconductor dual-mode hydrogen sensor, characterized in that: The overall structure is a Wheatstone bridge structure, including two parallel branches; The series element of one parallel branch is composed of a reference resistor A (11) and a reference resistor B (12); The series elements of the other parallel branch are composed of a parallel structure (13) and a catalytic combustion module A (14), wherein the parallel structure (13) is composed of a catalytic combustion module B (7a) and a semiconductor module (8); The reference resistor (11) and the parallel structure (13) have the same resistance value at room temperature and pressure, and the reference resistor (12) and the catalytic combustion module A (14) have the same resistance value at room temperature and pressure; The hydrogen concentration is determined by the voltage difference between the two series elements in each of the two parallel branches; The catalytic combustion module B (7a) and the semiconductor module (8) are coated with a catalytic gas-sensitive layer Pt catalyst.

2. The sensor according to claim 1, characterized in that The material of the semiconductor module (8) is In2O3 or SnO2 doped with transition elements.

3. The sensor according to claim 2, characterized in that The transition elements doped in the semiconductor module (8) include Pb, Rh, Ru, Y, Zr, Nb, Mo, Tc, Cd, Ir, Os, Ta, Hf, lanthanide elements and actinide elements; the doping concentration is 0.01%-3%.

4. The sensor according to claim 1, characterized in that The shapes of the catalytic combustion module B (7a) and the catalytic combustion module A (14) include a straight line, and a width of 0.01 cm-5 cm.

5. The sensor according to claim 1, characterized in that The shape of the material of the semiconductor module (8) includes a straight line, and the width is 0.01 cm-2 cm.

6. The sensor according to claim 1, characterized in that Also includes: A heating electrode (2), a ceramic substrate (5), a heat-insulating layer (4), a silicon substrate (6), and a conductive material (9).

7. The sensor according to claim 6, characterized in that The conductive material (9) is one of Pt, Au, Ag, Cu, Al, Ni, W, Ag / Pd alloy, and Pt / Au alloy.

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