CN103728359A - NOx sensor and preparation method thereof - Google Patents

Abstract

The invention discloses an NOx sensor and a preparation method thereof. The NOx sensor comprises an aluminum oxide heating body and a zirconium oxide substrate arranged on the aluminum oxide heating body, wherein two platinum electrodes are arranged on the surface of the zirconium oxide substrate, and an NOx sensitive electrode is arranged on one of the platinum electrodes. The sensor is prepared by the following steps: firstly adhering the zirconium oxide substrate on the aluminum oxide heating body, then printing two Pt electrodes on the surface of the zirconium oxide substrate, co-firing for 2-4 hours at 1350-1500 DEG C, then printing the NOx sensitive electrode on one of the Pt electrodes, and calcining for 2-4 hours at 500-700 DEG C. The sensitive electrode with high selectivity for NOx is arranged, and the electromotive force generated by the NOx in tail gas is directly measured, so that the concentration of the NOx can be obtained, and the test for low-concentration NOx has high sensitivity.

Description

A kind of NO xsensor and preparation method thereof

Technical field

The present invention relates to a kind of NO _xsensor and preparation method thereof.

Background technology

Along with the acceleration of China's Development of China's Urbanization, fossil fuel consumption increases sharply, and a lot of poisonous, harmful gases are released to contaminated environment in atmosphere, and wherein a most typical class, is exactly NO _xgas, it not only can cause photo-chemical smog and acid rain, damage the ozone layer, and also can produce harm to the mankind's respiratory system, occurs degradation symptom under alopecia, throat inflammation, visual impairment, respiratory system resistibility.Therefore oxides of nitrogen reduces discharging and is listed in one of requirement of environmental protection.Research shows, 75% NO _xgas is produced by motor vehicle emission, and this is wherein only about half of is to be produced by the vehicle of non-road transport, and as engineering machinery, agricultural machinery etc., these mechanical life-spans will be far longer than road transport vehicle simultaneously, and these motor vehicles and machines are reduced to NO _xdischarge just become more effective.Therefore people have dropped into very large energy and financial resources and reduce the generation of this gas and limit this class gas purging by more severe rules, for example the rules and regulations in U.S. Dec in 2000 2007 and later load-carrying vehicle NO _xdischarge must be at 0.20g/bhp.In Japan, stipulated NO _xemission standard at 0.25g/km.Similar standard has also been stipulated in Europe.China has also stipulated NO in state's four standards _xemission standard.

In automobile industry, reduce NO _xmethod mainly contain two kinds, NO _xgas entrapment and NO _xreduction.But no matter which kind of method, measures NO accurately _xconcentration be the problem that first will solve.

NO _xdetection method have a variety ofly, as resonance ionization spectroscopy method, fourier transform infrared spectrometry method, By Gas Chromatography-mass Spectrometry, chemiluminescence analysis etc., these methods can be measured NO very accurately _xconcentration, but also have a lot of shortcomings, as can not on-line testing, testing apparatus be bulky etc., these shortcomings cause said method all can not be applied to the processing of vehicle exhaust.

NO on present market _xsensor is the electrochemical source of current method of testing based on zirconia base, adopts 6 layers of zirconium oxide substrate lamination to burn and form altogether, and centre has added calandria, test electrode, oxygen pump electrode etc., and it is first by reducing the O in vehicle exhaust ₂content, by O in tail gas ₂content has dropped to very low degree (10 ^-3 _ppm), make NO _xgas becomes N at test electrode Surface disintegration ₂and O ₂gas, by measuring O ₂the strength of current of γ-ray emission, test NO _xconcentration.The advantage of this device is can on-line testing NO _xconcentration, volume is little, easy for installation, but its shortcoming is also clearly, first at NO _xconcentration very low time, decompose the O obtaining ₂the concentration of gas is also very low, and the electric current of generation is just very little, when analyzing very little electric current, the cost of subsequent process circuit has just increased, and in the situation that not increasing circuit cost, only has and has reduced the sensitivity of test, that is to say, this device is difficult to the lower NO of test _xconcentration; Secondly complicated process of preparation, has a lot of preparation processes, and the words of any step error in these steps all can cause that all that has been achieved is spoiled.

Summary of the invention

The problems referred to above that exist for prior art, the present invention aims to provide a kind of zirconia base NO _xsensor and preparation method thereof, to improve NO _xthe measurement sensitivity of sensor.

For achieving the above object, the technical solution used in the present invention is as follows:

A kind of NO _xsensor, comprising: aluminium oxide calandria and be arranged on the zirconium oxide substrate on described aluminium oxide calandria, is characterized in that: on the surface of described zirconium oxide substrate, be provided with two platinum electrodes, the platinum electrode described in is provided with NO therein _xsensitive electrode.

As preferred version, described NO _xsensitive electrode adopts the mesoporous zirconia material by the modified oxide of transition metal.

As further preferred version, the mesoporous zirconia material of the described modified oxide by transition metal is adopted and is prepared with the following method and obtain: first mesoporous zirconia material is flooded 1～4 hour in the acidic salt aqueous solution of transition metal, then take out and dry, then at 500～600 ℃, calcine 2 hours; Repeat aforesaid operations 2～3 times.

As preferred version further, the nitrate that the acidic salt of described transition metal is transition metal or sulfate.

As further preferred version, the oxide of described transition metal is selected from Cr ₂o ₃, Cu ₂o, Fe ₂o ₃, a kind of in NiO, ZnO and SnO.

A kind ofly prepare NO of the present invention _xthe method of sensor, comprises the steps:

A) zirconium oxide substrate is sticked on aluminium oxide calandria;

B) on the surface printing of zirconium oxide substrate, after two Pt electrodes, at 1350～1500 ℃, burn altogether 2～4 hours, obtain the zirconium oxide substrate with electrode;

C) on a Pt electrode therein, print NO _xsensitive electrode is then calcined 2～4 hours at 500～700 ℃, obtains described NO _xsensor.

As preferred version, described aluminium oxide calandria comprises two aluminium bases and is embedded the platinum electrode between two aluminium bases.

Compared with prior art, NOx sensor provided by the invention adopt 3 layer laminate altogether burning mode prepare, middle one deck is reference gas passage, its inner electrode is Pt, and external electrode comprises one deck Pt electrode and covers the NO that the mesoporous zirconia material modified by transition metal on Pt electrode forms _xsensitive electrode.Because sensitive electrode has high selectivity for NOx, therefore, the present invention is by sensitive electrode NOx to high selectivity is set, and the electromotive force producing by NOx in direct mensuration tail gas, just can draw NO _xconcentration, to low concentration of NO _xtest there is high sensitivity.

Accompanying drawing explanation

Fig. 1 is NO provided by the invention _xthe structural representation of sensor;

Fig. 2 is NO of the present invention _xthe structural representation of the aluminium oxide calandria in sensor;

Fig. 3 is NO provided by the invention _xsensor is to variable concentrations NO ₂response curve.

Embodiment

Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiment are only not used in and limit the scope of the invention for the present invention is described.

Embodiment 1

One, take cetyl trimethyl ammonium bromide as masterplate agent, utilize hydro-thermal synthesis process, synthesising mesoporous zirconia material, (concrete synthetic method is referring to " high specific surface area ordered porous zirconia synthetic with characterize ", < < Journal of Inorganic Materials > > 2000.6), synthetic mesoporous zirconia material is immersed to Cr (NO ₃) ₃aqueous solution 1～4 hour, then dries, and calcines 2 hours at 500～600 ℃; Repeat aforesaid operations 2～3 times, obtain by Cr ₂o ₃the mesoporous zirconia material of modifying;

Two, the zirconium oxide substrate of flow casting molding is sticked on aluminium oxide calandria after cutting out, then on the surface of zirconium oxide substrate, print two Pt electrodes, then at 1350～1500 ℃, burn altogether 2～4 hours, obtain the zirconium oxide substrate with electrode;

Three, on a Pt electrode therein printing by Cr ₂o ₃the NO that the mesoporous zirconia material of modifying forms _xsensitive electrode is then calcined 2～4 hours at 500～700 ℃, obtains NO _xsensor.

The NO that the present invention is prepared _xthe structure of sensor is as shown in Figure 1: on aluminium oxide calandria 1, be pasted with zirconium oxide substrate 2, the surface of zirconium oxide substrate 2 is provided with two platinum electrodes 3, and the platinum electrode described in 3 is provided with NO therein _xsensitive electrode 4; The structure of aluminium oxide calandria 1 is wherein as shown in Figure 2: between two aluminum oxide substrates 11, be embedded with platinum electrode 12.

To variable concentrations NO ₂response experiment: in the mixed gas of the oxygen of 5v/v% and the nitrogen of 95v/v%, add respectively and take the nitrogen dioxide gas of 100ppm, 200ppm that mixed gas cumulative volume is standard meter, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, then adopt NO provided by the invention _xsensor is tested respectively the responsiveness to nitrogen dioxide under various nitrogen dioxide gas content, its test result as shown in Figure 3, as seen from Figure 3: along with NO ₂the increase of concentration, the electromotive force of generation increases thereupon, further illustrates NOx sensor of the present invention NOx concentration is had to high sensitivity.

Finally be necessary described herein: above embodiment is only for being described in more detail technical scheme of the present invention; can not be interpreted as limiting the scope of the invention, some nonessential improvement that those skilled in the art's foregoing according to the present invention is made and adjustment all belong to protection scope of the present invention.

Claims (7)

1. a NO _xsensor, comprising: aluminium oxide calandria and be arranged on the zirconium oxide substrate on described aluminium oxide calandria, is characterized in that: the surface of described zirconium oxide substrate is provided with two platinum electrodes, and the platinum electrode described in is provided with NO therein _xsensitive electrode.

2. NO as claimed in claim 1 _xsensor, is characterized in that: described NO _xsensitive electrode adopts the mesoporous zirconia material by the modified oxide of transition metal.

3. NO as claimed in claim 2 _xsensor, it is characterized in that, the mesoporous zirconia material of the described modified oxide by transition metal is adopted and is prepared with the following method and obtain: first mesoporous zirconia material is flooded 1～4 hour in the acidic salt aqueous solution of transition metal, then take out and dry, then at 500～600 ℃, calcine 2 hours; Repeat aforesaid operations 2～3 times.

4. NO as claimed in claim 3 _xsensor, is characterized in that: the nitrate that the acidic salt of described transition metal is transition metal or sulfate.

5. NO as claimed in claim 2 or claim 3 _xsensor, is characterized in that: the oxide of described transition metal is selected from Cr ₂o ₃, Cu ₂o, Fe ₂o ₃, a kind of in NiO, ZnO and SnO.

6. prepare NO claimed in claim 1 for one kind _xthe method of sensor, is characterized in that, comprises the steps:

A) zirconium oxide substrate is sticked on aluminium oxide calandria;

B) on the surface printing of zirconium oxide substrate, after two Pt electrodes, at 1350～1500 ℃, burn altogether 2～4 hours, obtain the zirconium oxide substrate with electrode;

C) on a Pt electrode therein, print NO _xsensitive electrode is then calcined 2～4 hours at 500～700 ℃, obtains described NO _xsensor.

7. method as claimed in claim 6, is characterized in that: described aluminium oxide calandria comprises two aluminium bases and is embedded the platinum electrode between two aluminium bases.

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