CN115745000A - Pt-modified multi-element metal oxide sensitive material and preparation method and application thereof - Google Patents

Abstract

The invention discloses a preparation method of a Pt modified multi-element metal oxide sensitive material, which comprises the following steps: s1: sequentially adding iron salt, a precipitator and one or more other transition metal salts into deionized water, and stirring to obtain a uniformly mixed solution A; s2: putting the mixed solution A into a reaction kettle with a polytetrafluoroethylene lining, heating to 120 ℃, and preserving heat for 8-12 h; s3: the material is calcined for 3 hours at 300 ℃ under the air condition after being centrifuged, washed and dried to obtain FeMO _x A sensitive material; s4: feMO is mixed _x Dispersing the sensitive material in an ethanol solution to obtain a solution B; s5: slowly adding the chloroplatinic acid solution into the solution B drop by drop, stirring, washing and drying; s6: placing the materials in H ₂ Heating to 120 deg.C under Ar atmosphere, holding for 2 hr, and cooling to room temperature to obtainPt/FeMO _x A sensitive material. The defect types and the number of the prepared gas sensitive materials are increased, and the sensitivity, the stability and the selectivity of the hydrogen sensor prepared by adopting the gas sensitive materials are obviously improved.

Description

A Pt-modified multi-element metal oxide sensitive material and its preparation method and application

technical field

The invention belongs to the field of semiconductor metal oxide gas sensors, and in particular relates to a Pt-modified multi-element metal oxide sensitive material for improving the performance of a hydrogen sensor, a preparation method and an application thereof.

Background technique

Hydrogen is a common reducing agent in industrial production and has a wide range of uses. It is worth noting that hydrogen is a colorless and odorless gas, which has the characteristics of high diffusivity, high combustion heat and low explosion concentration in the air, which has caused great attention to the safety of hydrogen during transportation and use. . Semiconductor metal oxide gas sensors are widely used in the detection of toxic gases, flammable and explosive gases, and industrial waste gases due to their advantages of high stability, low cost, and simple manufacturing process. However, the sensitive materials of semiconductor metal oxide gas sensors still face problems such as low sensitivity, long response/recovery time, and poor selectivity, which need to be solved. Therefore, the development of a gas sensor with high sensitivity, fast response, high selectivity and low concentration detection has been of great interest.

In order to develop semiconductor metal oxide sensitive materials with high sensitivity, fast response/recovery speed and low concentration detection, Chinese patent application number CN201910260163.6 discloses a method for preparing Pt-modified _SnO2 nanorod sensitive materials. The prepared The aspect ratio of SnO ₂ nanorods is high, and the Pt nanoparticles are uniformly dispersed on the surface of SnO ₂ nanorods by using the ultraviolet light reduction method, so that the sensor shows a significant change in resistance at a lower hydrogen concentration. The Chinese patent application number CN201110137838.1 discloses a composite sensitive material of Pt and Pd loaded TiO ₂ , the sensitive material is made of TiO ₂ by anodizing high-purity titanium sheet twice, and then precious metal particles (Pt and Pd) deposited onto _TiO2 nanotubes. The noble metal coating accelerates the interaction of _H2 with the surface of _TiO2 nanotubes and improves the hydrogen sensitivity. The Chinese patent with application number CN201510760530.0 discloses a method for preparing Pt/Pd nanoparticles sputtering molybdenum oxide fiber paper. The sensor prepared by this method can work at room temperature, has high sensitivity, and has the advantages of short response/recovery time. The improvement of the performance of the above gas sensors mainly depends on the combination of noble metal Pt/Pd and a single metal oxide, which improves the sensor in terms of operating temperature, sensitivity, response/recovery time, etc., but the type and quantity of defects in the single metal oxide The limited and noble metal Pt/Pd nanoparticles loading increases the cost of the sensor.

Contents of the invention

An object of the present invention is to provide a method for preparing a Pt-modified multi-element metal oxide sensitive material to improve the sensitivity, stability and response/recovery time of the hydrogen sensor.

In order to achieve the above object of the invention, the invention provides a method for preparing a Pt-modified multi-element metal oxide sensitive material, comprising the following steps:

S1: Add iron salt, precipitant and one or more other transition metal salts into deionized water in sequence, and stir to obtain a uniformly mixed solution A;

S2: Put the mixed solution A into a reaction kettle lined with polytetrafluoroethylene, heat it to 120°C, and keep it warm for 8h-12h;

S3: centrifuging, washing and drying the material obtained in step S2, and calcining at 300° C. under air conditions for 3 hours to obtain a FeMO _x sensitive material;

S4: Dispersing the FeMO _x sensitive material obtained in step S3 in an ethanol solution to obtain a uniformly mixed solution B;

S5: Add the chloroplatinic acid solution slowly and dropwise to the solution B, stir for 3 hours, wash and dry;

S6: Heating the material obtained in step S5 to 120° C. under H ₂ /Ar atmosphere, keeping the temperature for 2 hours, and then cooling to room temperature to obtain a Pt/FeMO _x sensitive material. Wherein, M refers to other transition metal elements except iron.

Compared with the prior art, the present invention uses Fe ₂ O ₃ with narrow band gap, high stability, low cost and environmental friendliness as the substrate, doped with other avalent metals, and adopts a simple hydrothermal synthesis method to synthesize in one step A multi-defect multi-element metal oxide sensitive material, and the noble metal Pt is atomically dispersed on the surface of the metal oxide, which significantly improves the gas sensing performance of the gas sensor. The Pt-modified multi-element metal oxide sensitive material prepared by the invention has obvious increase in defect types and quantities compared with the prior sensitive material compounded by Pt/Pd and a single metal oxide. Its preparation method is simple, low in cost, strong in repeatability and does not require surfactants.

Preferably, in step S1, the molar ratio of the metal element to the precipitant is 1: (2-5); among the metal elements, the molar ratio of the iron element to other transition metal elements (M) is 1: (1-3).

Preferably, in step S1, the molar ratio of iron salt, precipitant, one or more other transition metal salts and deionized water is 1:(4.36-10):(0-3):(2700-4370).

Preferably, in step S5, the concentration of the chloroplatinic acid solution is 50 mg mL ^-1 , and the molar ratio of the platinum element in the chloroplatinic acid to the metal element in solution B is 1: (200-400).

Preferably, in step S1, the iron salt is any one of FeCl ₃ , Fe ₂ (SO ₄ ) ₃ , and Fe(NO ₃ ) ₃ .

Preferably, in step S1, the other transition metal salts are other transition metal chlorides or transition metal sulfides except iron salts. Other transition metal salts can be used such as: copper chloride, zinc chloride, manganese chloride, chromium chloride, titanium chloride, molybdenum chloride, tungsten chloride and other transition metal chlorides, or manganese sulfate, zinc sulfate, molybdenum sulfate , niobium sulfate, copper sulfate and other transition metal sulfides.

Preferably, in step S1, the precipitating agent is any one of urea and ammonium fluoride or a mixture of both.

The present invention also provides a Pt-modified multi-element metal oxide sensitive material prepared by the above-mentioned preparation method, which has significantly increased defect types and quantities compared with existing Pt/Pd and single metal oxide composite sensitive materials .

The present invention also provides the application of the above-mentioned Pt-modified multi-element metal oxide sensitive material in a hydrogen sensor. The Pt-modified multi-element metal oxide sensitive material is used as the gas-sensing material of the hydrogen sensor, which can effectively improve the sensitivity, response/recovery time, selectivity and stability of the hydrogen sensor.

The Pt-modified multi-element metal oxide sensitive material prepared by the invention has obvious increase in defect types and quantities. Its preparation method is simple, low in cost, strong in repeatability and does not require surfactants. Experimental test results show that the Pt-modified multi-component metal oxide sensor has significantly improved sensitivity, response/recovery time, selectivity and stability compared with existing hydrogen sensors.

Description of drawings

Fig. 1 is the SEM picture of the _Fe2O3 sensitive material that comparative example 1 makes _;

Fig. 2 is the SEM picture of the Pt/Fe ₂ (MoO ₄ ) ₃ sensitive material that embodiment 1 makes;

Fig. 3 is the SEM picture of the Pt/ZnFe ₂ O ₄ sensitive materials prepared by embodiment 3;

Fig. 4 is the sensitivity variation curve graph to 10ppm hydrogen of the hydrogen sensor that adopts the sensitive material that embodiment 1, embodiment 2, embodiment 3, comparative example 1 and comparative example 2 make to make at different temperatures;

Fig. 5 is the continuous dynamic response curve of the hydrogen sensor made of the sensitive material made in embodiment 1 at optimum operating temperature and different hydrogen concentrations;

Fig. 6 is the continuous dynamic response curve of the hydrogen sensor made of the sensitive material made in embodiment 3 at optimum operating temperature and different hydrogen concentrations;

Fig. 7 is the continuous dynamic response curve under optimum operating temperature and 10ppm hydrogen concentration of the hydrogen sensor made by the sensitive material adopted in embodiment 1;

Fig. 8 is the continuous dynamic response curve of the hydrogen sensor made of the sensitive material made in embodiment 3 at optimum operating temperature and 10ppm hydrogen concentration;

Fig. 9 is a graph showing changes in the response values of hydrogen sensors made of the sensitive materials prepared in Example 1 and Example 3 to 10 ppm hydrogen, carbon monoxide and methane at the optimum operating temperature.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that the implementation of the present invention is not limited to the following examples, and any modifications or changes in form based on the present invention will fall within the scope of the present invention. As the embodiment of the present invention only lists two Pt-modified multi-element metal oxide sensitive materials (Pt/Fe ₂ (MoO ₄ ) ₃ and Pt/ZnFeO ₄ ), it is not limited to these two Pt-modified multi-element metal oxides Sensitive materials, those skilled in the art can be replaced by other avalent metals doped in the α-Fe ₂ O ₃ matrix, and the amount of reagents and raw materials and experimental conditions can also be adjusted within the parameters defined in the claims. All should be regarded as belonging to the scope of the present invention.

In the present invention, the equipment and raw materials used can be purchased from the market or commonly used in this field. The following are the main reagents used in the examples:

Example 1:

The Pt/Fe ₂ (MoO ₄ ) ₃ sensitive material was prepared according to the following steps:

Take 0.41g Fe(NO ₃ ) ₃ 9H ₂ O, 3.76g (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O, 0.116g NH ₄ F and 0.308g CN ₂ H ₄ O (the mixture of metal element and precipitation agent The molar ratio is 1:2, and the ratio of iron element to other transition metal elements is 1:3) into 70mL deionized water in turn (the molar ratio of iron element: precipitant: molybdenum element: deionized water is 1:8:3:3851) , and stirred for 40 min to obtain a uniformly mixed liquid. Put the uniformly mixed liquid into a 100mL reaction kettle with a polytetrafluoroethylene liner, heat it to 120°C, keep it warm for 8 hours, and cool it down to room temperature naturally. Dilute the suspension with deionized water and ethanol (3:1 ) was washed at least 3 times, and then dried at 60°C for 17 hours to obtain a dry powder sample. Finally, the powder sample was calcined at 300°C in air for 3 hours with a heating rate of 5°C/min to obtain the Fe ₂ (MoO ₄ ) ₃ gas-sensing material. Take 100mg of the Fe ₂ (MoO ₄ ) ₃ sample prepared above and add it into 10 mL of ethanol solution, and perform ultrasonic and stirring intermittently until the Fe ₂ (MoO ₄ ) ₃ powder is evenly dispersed in the ethanol solution. Take 166 μL, 50 mg mL ^-1 of H ₂ PtCl ₆ solution (the molar ratio of platinum element to transition metal element (Fe and Mo) is 1:200) and slowly and dropwise add it to the above-mentioned Fe ₂ (MoO ₄ ) ₃ ethanol and mix solution, stirred for 3 hours, washed and freeze-dried to obtain a powder sample. The powder sample obtained above was heated to 120°C under 10% H ₂ /Ar atmosphere at a heating rate of 2°C min ^-1 , kept for 2 hours, then cooled to room temperature to obtain a Pt/Fe ₂ (MoO ₄ ) ₃ sensitive material .

Example 2:

The Pt/Fe ₂ (MoO ₄ ) ₃ sensitive material was prepared according to the following steps:

Take 0.58g Fe(NO ₃ ) ₃ 9H ₂ O, 3.22g (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O, 0.160g NH ₄ F and 0.423g CN ₂ H ₄ O (the mixture of metal element and precipitation agent The molar ratio is 1:2.75, and the molar ratio of iron element to transition metal element is 1:1.8) into 70mL deionized water in turn (the molar ratio of iron element: precipitant: molybdenum element: deionized water is 1:7.7:1.8:2700) , and stirred for 40 min to obtain a uniformly mixed liquid. Put the uniformly mixed liquid into a 100mL reaction kettle with a polytetrafluoroethylene liner, heat it to 120°C, keep it warm for 8 hours, and cool it down to room temperature naturally. Dilute the suspension with deionized water and ethanol (3:1 ) was washed at least 3 times, and then dried at 60°C for 17 hours to obtain a dry powder sample. Finally, the powder sample was calcined at 300°C in air for 3 hours with a heating rate of 5°C/min to obtain the Fe ₂ (MoO ₄ ) ₃ gas-sensing material. Take 100mg of the Fe ₂ (MoO ₄ ) ₃ sample prepared above and add it into 10 mL of ethanol solution, and perform ultrasonic and stirring intermittently until the Fe ₂ (MoO ₄ ) ₃ powder is evenly dispersed in the ethanol solution. Take 110 μL, 50 mg mL ^-1 of H ₂ PtCl ₆ solution (the molar ratio of platinum element to transition metal element (Fe and Mo) is 1:300) and slowly and dropwise add it to the above-mentioned Fe ₂ (MoO ₄ ) ₃ ethanol and mix solution, stirred for 3 hours, washed and freeze-dried to obtain a powder sample. The powder sample obtained above was heated to 120°C under 10% H ₂ /Ar atmosphere at a heating rate of 2°C min ^-1 , kept for 2 hours, then cooled to room temperature to obtain a Pt/Fe ₂ (MoO ₄ ) ₃ sensitive material .

Example 3:

Prepare Pt/ZnFe ₂ O ₄ sensitive material as follows:

Take 0.36g Fe(NO ₃ ) ₃ 9H ₂ O, 0.12g ZnCl ₂ , 0.116g NH ₄ F and 0.364g CN ₂ H ₄ O (the molar ratio of metal element to precipitation agent is 1:5, iron element and transition The ratio of metal elements is 1:1) into 70mL deionized water (the molar ratio of iron element: precipitant: molybdenum element: deionized water is 1:10:1:4370) in sequence, and stirred for 40min to obtain a uniformly mixed liquid. Put the uniformly mixed liquid into a 100mL reaction kettle with a polytetrafluoroethylene liner, heat it to 120°C, keep it warm for 8 hours, and cool it down to room temperature naturally. Dilute the suspension with deionized water and ethanol (3:1 ) was washed at least 3 times, and then dried at 60°C for 17 hours to obtain a dry powder sample. Finally, the powder sample was calcined at 300°C in air for 3 hours with a heating rate of 5°C/min to obtain the ZnFe ₂ O ₄ sensitive material. Take 100mg of the ZnFe ₂ O ₄ sample prepared above and add it into 10mL ethanol solution, ultrasonicate and stir intermittently until the ZnFe ₂ O ₄ powder is evenly dispersed in the ethanol solution. Take 37.0 μL, 50 mgmL ^-1 of H ₂ PtCl ₆ (the molar ratio of platinum element to transition metal element (Fe and Zn) is 1:400) solution and slowly and dropwise add it to the above ZnFe ₂ O ₄ ethanol mixed solution, After stirring for 3 hours, it was washed and freeze-dried to obtain a powder sample. The powder sample obtained above was heated to 120°C in a 10% H ₂ /Ar atmosphere at a heating rate of 2°C min ^-1 , kept for 2 hours, then cooled to room temperature to obtain a Pt/ZnFe ₂ O ₄ sensitive material.

Comparative example 1:

Prepare _Fe2O3 gas-sensing material according _to the following steps

Take 0.41g FeCl ₃ 6H ₂ O, 0.05g NH ₄ F and 0.189g CN ₂ H ₄ O (the molar ratio of metal element to precipitant is 1:4.36) and add them into 70mL deionized water (iron element: precipitant: The molar ratio of deionized water is 1:4.36:3851), and stirred for 40 minutes to obtain a uniformly mixed liquid. Put the uniformly mixed liquid into a 100mL reaction kettle with a polytetrafluoroethylene liner, heat it to 120°C, keep it warm for 8 hours, and cool it down to room temperature naturally. Dilute the suspension with deionized water and ethanol (3:1 ) was washed at least 3 times, and then dried at 60°C for 17 hours to obtain a dry powder sample. Finally, the powder sample was calcined at 300°C in air for 3 hours with a heating rate of 5°C/min to obtain the Fe ₂ O ₃ sensitive material. Comparative example 2:

Prepare Pt/Fe ₂ O ₃ sensitive materials as follows:

Take 0.41g FeCl ₃ 6H ₂ O, 0.05g NH ₄ F and 0.189g CN ₂ H ₄ O (the molar ratio of metal element to precipitant is 1:4.36) and add them into 70mL deionized water (iron element: precipitant: The molar ratio of deionized water is 1:4.36:3851), and stirred for 40 minutes to obtain a uniformly mixed liquid. Put the uniformly mixed liquid into a 100mL reaction kettle with a polytetrafluoroethylene liner, heat it to 120°C, keep it warm for 8 hours, and cool it down to room temperature naturally. Dilute the suspension with deionized water and ethanol (3:1 ) was washed at least 3 times, and then dried at 60°C for 17 hours to obtain a dry powder sample. Finally, the powder sample was calcined at 300°C in air for 3 hours with a heating rate of 5°C/min to obtain the Fe ₂ O ₃ sensitive material. Take 100mg of the sample prepared above and add it into 10mL ethanol solution, ultrasonicate and stir intermittently until the Fe ₂ O ₃ powder is evenly dispersed in the ethanol solution. Take 24.0 μL, 50 mg mL ^-1 of H ₂ PtCl ₆ (the molar ratio of platinum element to Fe element is 1:350) solution and slowly and dropwise add it to the above Fe ₂ O ₃ ethanol mixed solution, stir for 3 hours and then wash , freeze-drying to obtain a powder sample. The powder sample obtained above was heated to 120°C in a 10% H ₂ /Ar atmosphere at a heating rate of 2°C min ^-1 , kept for 2 hours, then cooled to room temperature to obtain a Pt/Fe ₂ O ₃ sensitive material.

Analysis of test results:

From the SEM image of Figure 1, it can be observed that the Fe ₂ O ₃ sensitive material prepared in Comparative Example 1 mainly exists in the shape of lines and polyhedrons, and the surface is smooth. From _the SEM image of Figure 2, it can be seen that the Pt/Fe ₂ (MoO ₄ ) ₃ sensitive material prepared in Example 1 presents a flower-like morphology composed _of nanowires, and there is _no The presence of Pt nanoparticles was observed on the surface, which was due to the small amount of Pt loading, and Pt was dispersed in the form of atoms on the surface of Fe ₂ (MoO ₄ ) ₃ . It can be seen from the SEM image of FIG. 3 that the Pt/ZnFe ₂ O ₄ sensitive material prepared in Example 3 is composed of nanowire stacks. From the SEM images of 1 to 3, it can be seen that the preparation method provided by the present invention successfully prepared Fe ₂ O ₃ sensitive materials, Pt/Fe ₂ (MoO ₄ ) ₃ sensitive materials and Pt/ZnFe ₂ O ₄ sensitive materials. As can be seen from Figure 4, the _Fe2O3 sensor made of the sensitive material made in Comparative Example 1, _the Pt/ _Fe2O3 sensor made of the sensitive material made in _Comparative Example 2, the sensor made of the sensitive material made in Example 1 The Pt/Fe ₂ (MoO ₄ ) ₃ sensor made of sensitive material, the Pt/Fe ₂ (MoO ₄ ) ₃ sensor made of the sensitive material made in Example 2 and the sensitive material made in Example 3 The response value of the Pt/ZnFe ₂ O ₄ sensor is under the condition of 10ppm hydrogen, as the temperature increases, the response value first rises to the maximum value and then decreases. At the same temperature, the Pt/Fe ₂ (MoO ₄ ) ₃ sensor made of the sensitive material made in Example 1 is compared with the Pt/ZnFe ₂ O ₄ sensor made of the sensitive material made in Example 3. The Fe ₂ O ₃ sensor made of the sensitive material made in ratio 1, the Pt/Fe 2 O 3 sensor made of the sensitive material made in comparative example 2, and the Pt/Fe ₂ O ₃ sensor made of the sensitive material made in embodiment 2 The response value of the Fe ₂ (MoO ₄ ) ₃ sensor is greatly improved. It can be seen from Fig. 5 that at 300°C, the response value of the Pt/Fe ₂ (MoO ₄ ) ₃ sensor made of the sensitive material prepared in Example 1 increases with the increase of the hydrogen concentration. It can be seen from Fig. 6 that at 300°C, the response value of the Pt/ZnFe ₂ O ₄ sensor made of the sensitive material prepared in Example 3 increases with the increase of the hydrogen concentration. It can be seen from Fig. 7 that under the conditions of 300°C and 10 ppm hydrogen gas, the Pt/Fe ₂ (MoO ₄ ) ₃ hydrogen sensor made of the sensitive material prepared in Example 1 has high stability and short response/recovery time. It can be seen from Fig. 8 that under the conditions of 300°C and 10 ppm hydrogen gas, the Pt/ZnFe ₂ O ₄ hydrogen sensor made of the sensitive material prepared in Example 3 has high stability and no baseline shift occurs. According to the histogram in Figure 9, it can be seen that the Pt/Fe ₂ (MoO ₄ ) ₃ gas sensor made of the sensitive material made in Example 1 and the Pt/ZnFe ₂ O ₄ made of the sensitive material made in Example 3 The gas sensor has high selectivity to hydrogen.

The above performance data show that the Pt/Fe ₂ (MoO ₄ ) ₃ gas sensor prepared in Example 2 has a limited improvement in hydrogen sensitivity, while the Pt-modified multi-component Fe ₂ O 3 prepared in Example 1 and Example ₃ As the gas-sensing material of hydrogen sensor, the hydrogen sensor made has obvious advantages in response value, stability, response time and selectivity.

The present invention is not limited to the application listed in the specification and implementation, and it can be applied to various fields suitable for the present invention. Without departing from the spirit and essence of the present invention, for those familiar with the field, Other modifications and variations can be easily realized, but these corresponding modifications and variations should all belong to the scope of protection required by the present invention.

The above descriptions are only part of the embodiments of the present invention, and are not intended to limit the implementation and protection scope of the present invention. For those skilled in the art, they should be able to realize that all equivalent replacements made by using the content of the description of the present invention are obvious and obvious The scheme obtained by the change should be included in the protection scope of the present invention.

Claims (9)

1. A preparation method of a Pt modified multi-element metal oxide sensitive material is characterized by comprising the following steps: the method comprises the following steps:

s1: sequentially adding ferric salt, a precipitator and one or more other transition metal salts into deionized water, and stirring to obtain a uniformly mixed solution A;

s2: putting the mixed solution A into a reaction kettle with a polytetrafluoroethylene lining, heating to 120 ℃, and preserving heat for 8-12 h;

s3: the material obtained in the step S2 is calcined for 3 hours at 300 ℃ under the air condition after being centrifuged, washed and dried to obtain FeMO _x A sensitive material;

s4: feMO obtained in step S3 _x Dispersing the sensitive material in an ethanol solution to obtain a uniformly mixed solution B;

s5: slowly and dropwise adding the chloroplatinic acid solution into the solution B, stirring for 3 hours, and then washing and drying;

s6: the material obtained in the step S5 is added into H ₂ Heating to 120 ℃ under the Ar atmosphere, preserving heat for 2 hours, and cooling to room temperature to obtain Pt/FeMO _x A sensitive material.

2. The method of claim 1, wherein: in step S1, the molar ratio of the metal element to the precipitant is 1: (2-5); in the metal elements, the molar ratio of the iron element to other transition metal elements is 1: (1-3).

3. The method of claim 1, wherein: in step S1, the molar ratio of the ferric salt, the precipitating agent, the one or more other transition metal salts, and the deionized water is 1: (4.36-10): (0 to 3): (2700-4370).

4. The method of claim 1, wherein: in step S5, the concentration of the chloroplatinic acid solution is 50mgmL ^-1 And the molar ratio of the platinum element in the chloroplatinic acid to the metal element in the solution B is 1: (200-400).

5. The method of claim 1, wherein: in step S1, the ferric salt is FeCl ₃ 、Fe ₂ (SO ₄ ) ₃ 、Fe(NO ₃ ) ₃ Any one of the above.

6. The method of claim 1, wherein: in step S1, the other transition metal salt is a transition metal chloride or a transition metal sulfide other than the iron salt.

7. The method of claim 1, wherein: in step S1, the precipitating agent is any one of urea and ammonium fluoride or a mixture of both.

8. A Pt modified multi-element metal oxide sensitive material is characterized in that: prepared by the preparation method of any one of claims 1 to 7.

9. Pt modified multi-element Fe ₂ O ₃ The hydrogen sensor is characterized in that: the gas sensitive material is the Pt modified multi-element metal oxide sensitive material as defined in claim 8.

Images