CN114689651A - Nitrogen-oxygen sensor, nitrogen oxide measuring method and vehicle - Google Patents
Nitrogen-oxygen sensor, nitrogen oxide measuring method and vehicle Download PDFInfo
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- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 title claims abstract description 171
- DOTMOQHOJINYBL-UHFFFAOYSA-N molecular nitrogen;molecular oxygen Chemical compound N#N.O=O DOTMOQHOJINYBL-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 32
- 229910018885 Pt—Au Inorganic materials 0.000 claims abstract description 43
- 239000002131 composite material Substances 0.000 claims abstract description 42
- 239000000126 substance Substances 0.000 claims abstract description 26
- 229910002091 carbon monoxide Inorganic materials 0.000 claims abstract description 21
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 19
- 238000006243 chemical reaction Methods 0.000 claims abstract description 18
- 230000002829 reductive effect Effects 0.000 claims abstract description 14
- 230000008569 process Effects 0.000 claims abstract description 12
- 239000001301 oxygen Substances 0.000 claims description 58
- 229910052760 oxygen Inorganic materials 0.000 claims description 58
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 50
- 239000002245 particle Substances 0.000 claims description 43
- 238000007254 oxidation reaction Methods 0.000 claims description 14
- 230000003647 oxidation Effects 0.000 claims description 13
- 230000008859 change Effects 0.000 claims description 7
- 230000009467 reduction Effects 0.000 claims description 3
- AVXURJPOCDRRFD-UHFFFAOYSA-N Hydroxylamine Chemical class ON AVXURJPOCDRRFD-UHFFFAOYSA-N 0.000 claims 2
- 238000005259 measurement Methods 0.000 abstract description 26
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 40
- 239000010931 gold Substances 0.000 description 29
- 239000007789 gas Substances 0.000 description 24
- 239000007784 solid electrolyte Substances 0.000 description 14
- -1 oxygen ion Chemical class 0.000 description 8
- 229910052737 gold Inorganic materials 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 229910052697 platinum Inorganic materials 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 5
- 238000003916 acid precipitation Methods 0.000 description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 4
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 210000002858 crystal cell Anatomy 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 2
- 230000033116 oxidation-reduction process Effects 0.000 description 2
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 2
- 230000032258 transport Effects 0.000 description 2
- 229910001928 zirconium oxide Inorganic materials 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- 229910002089 NOx Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 238000004523 catalytic cracking Methods 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000003411 electrode reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000007794 irritation Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
- G01N33/0037—NOx
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- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Pathology (AREA)
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Abstract
The invention provides a nitrogen oxygen sensor, a nitrogen oxide measuring method and a vehicle, wherein the nitrogen oxygen sensor comprises: a first chamber, a second chamber; the first chamber is provided with a first pump electrode which is a Pt-Au composite electrode used for catalyzing HC, CO and H2At least one substance of (a); the second chamber is used for catalyzing NO reaction and obtaining the discharge amount of NO. According to the nitrogen-oxygen sensor disclosed by the embodiment of the invention, other substances which possibly influence the measurement of nitrogen oxides in automobile exhaust are pretreated by utilizing the Pt-Au composite electrode, and the trapping capacity of the Pt-Au composite electrode on substances containing H and CO is far higher than that of NO, so that the consumption of NO in the pretreatment process is reduced, the influence on the measurement of the nitrogen oxides is further reduced, and the accuracy of the measurement of the nitrogen oxides is improved.
Description
Technical Field
The invention relates to the technical field of vehicles, in particular to a nitrogen-oxygen sensor, a nitrogen oxide measuring method and a vehicle.
Background
Nitric oxides such as nitric oxide and nitrogen dioxide in automobile exhaust are discharged into the air and are finally converted into nitric acid and nitrate, and the nitric acid is one of the main causes of acid rain. In addition, nitrogen oxides such as nitric oxide and nitrogen dioxide have different degrees of irritation and toxicity to the human body.
In the field of vehicle technology, after an after-treatment system for automobile exhaust is used to treat emissions such as carbon monoxide, nitrogen oxides, hydrocarbons, and particulates in exhaust gas generated by an engine. Often still can use the nitrogen oxygen sensor to monitor the nitrogen oxide emission in the automobile exhaust to guarantee that the nitrogen oxide in the automobile exhaust can not exceed standard, reduce the atmospheric pollution, restrain the formation of acid rain.
Since the nitrogen oxides in the exhaust gas of automobiles are mainly NO, the related art mainly measures the emission amount of NO to represent the emission amount of nitrogen oxides. Other gases such as CO and H can be present in the automobile exhaust besides nitrogen oxides2These gases affect the measurement result in the process of measuring the amount of NO emission, and therefore, it is necessary to pretreat the automobile exhaust before measuring the amount of NO emission. However, in the process of pretreating the exhaust gas, the existing nitrogen-oxygen sensor often reflects a part of NO, which causes that the measurement of the NO emission is often not accurate enough.
Therefore, in order to further accurately monitor the emission amount of nitrogen oxides of a vehicle, it is required to improve the measurement accuracy of the nitrogen oxide sensor.
Disclosure of Invention
In view of the above, the present invention is directed to a nitrogen oxygen sensor, a method for measuring nitrogen oxide, and a vehicle, so as to solve the problem that the measurement accuracy of the existing nitrogen oxygen sensor needs to be improved.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a nitrogen oxygen sensor, comprising: a first chamber and a second chamber;
the first chamber is provided with a first pump electrode which is a Pt-Au composite electrodeThe Pt-Au composite electrode is used for catalyzing HC, CO and H2At least one substance of (a);
the second chamber is used for catalyzing NO reaction and obtaining the discharge amount of NO.
Further, Au in the Pt-Au composite electrode is applied to HC, CO and H2And the Pt in the Pt-Au composite electrode catalyzes oxygen elements to obtain electrons.
Furthermore, the Pt-Au composite electrode consists of Pt particles and Au particles which are distributed in a staggered mode, and HC, CO and H are completed by the Pt particles and the Au particles together2Capture and oxidation of at least one substance in (1).
Further, the diameter of the Pt particles is 5-10 microns, and the diameter of the Au particles is 0.1-1 micron.
Further, the second chamber is provided with a second pump electrode and a voltage sensor; the second pump electrode is used for catalyzing NO reaction, and the voltage sensor obtains the NO emission amount by detecting the difference between the oxygen content of the second chamber and the oxygen content of the outside air.
Compared with the prior art, the nitrogen-oxygen sensor has the following advantages:
the nitrogen-oxygen sensor comprises a first chamber and a second chamber, wherein the first chamber is pretreated before measurement, and the second chamber is used for detecting the discharge amount of NO; wherein, the Pt-Au composite electrode is utilized in the first chamber, and other substances which can influence the measurement of nitrogen oxides in the automobile exhaust, including HC, CO and H2And the Pt-Au composite electrode has capture capacity far exceeding that of NO for substances containing H and CO, so that the consumption of NO in the pretreatment process is reduced, the influence on the measurement of nitrogen oxide is further reduced, and the accuracy of the measurement of the nitrogen oxide is improved.
Another objective of the present invention is to provide a method for measuring nitrogen oxide, so as to solve the problem that the accuracy of the existing method for measuring nitrogen oxide needs to be improved.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a method for measuring nitrogen oxides, which is applied to the nitrogen-oxygen sensor in any one of the above embodiments, the method comprising:
in the process that the automobile exhaust is sequentially discharged into the first chamber and the second chamber of the nitrogen-oxygen sensor,
HC, CO and H contained in the automobile exhaust2Is adsorbed by the Pt-Au composite electrode and is oxidized into H in the first chamber2O and/or CO2；
NO in the automobile exhaust is reduced into N in the second cavity2And O2；
According to the O2The resulting oxygen flow voltage, in combination with the reference voltage, yields the NO emission.
Further, Au in the Pt-Au composite electrode is applied to HC, CO and H2And the Pt in the Pt-Au composite electrode catalyzes oxygen elements to obtain electrons.
Furthermore, the Pt-Au composite electrode consists of Pt particles and Au particles which are distributed in a staggered mode, and HC, CO and H are completed by the Pt particles and the Au particles together2Capture and oxidation of at least one substance in (1).
Further, a second pump electrode in the second chamber catalyzes the reduction of NO to N2And O2And the voltage sensor in the second chamber detects the difference change of the oxygen content between the second chamber and the outside air to obtain the NO emission.
Compared with the prior art, the method for measuring the nitrogen oxide has the following advantages:
according to the method for measuring the nitrogen oxide, in the process that the automobile exhaust is sequentially discharged into the first cavity and the second cavity of the nitrogen-oxygen sensor, the Pt-Au composite electrode is utilized in the first cavity, and other substances which can influence the measurement of the nitrogen oxide in the automobile exhaust and comprise HC, CO and H2The Pt-Au composite electrode has capture capability of H-containing substances and CO far exceeding that of NO, so that the consumption of NO in the pretreatment process is reduced,the influence on the measurement of the nitrogen oxide is further reduced, and the accuracy of the measurement of the nitrogen oxide is improved.
Another object of the present invention is to provide a vehicle to solve the problem of the existing aftertreatment system of the vehicle that the measurement accuracy of the nox needs to be improved.
A vehicle, an after-treatment system of the vehicle comprises the nitrogen oxygen sensor of any one of the above embodiments.
Compared with the prior art, the vehicle has the following advantages:
the vehicle provided by the embodiment of the invention comprises the nitrogen-oxygen sensor provided by any one of the embodiments, and HC, CO and H are firstly mixed by utilizing a Pt-Au composite electrode2The substances are pretreated, the trapping capacity of the Pt-Au composite electrode to the H-containing substance and CO is far higher than that of NO, NO is hardly consumed in advance in the pretreatment process, and then NO is measured after pretreatment, so that the influence on the measurement of the nitrogen oxide is effectively reduced, the accuracy of the measurement of the nitrogen oxide is improved, the accurate monitoring of the emission of the nitrogen oxide in the tail gas of the automobile can be realized, and further, the effective help is provided for preventing and treating the pollution of the atmospheric environment and inhibiting the formation of acid rain.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a simplified schematic diagram of a prior art NOx sensor;
FIG. 2 is a schematic structural diagram of a NI sensor according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the operation of an oxygen transport system according to an embodiment of the present invention;
FIG. 4 is a schematic cross-sectional view of a Pt-Au composite electrode according to an embodiment of the invention;
fig. 5 is a flowchart illustrating steps of a method for measuring nox according to an embodiment of the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
In the exhaust aftertreatment system of present automobile engine, nitrogen oxide sensor has been commonly used, and the emission of nitrogen oxide in the final exhaust of car is monitored, and then restricts the emission of the nitrogen oxide of vehicle, provides help for preventing and treating atmospheric environment's pollution and inhibiting the formation of acid rain.
Referring to fig. 1, fig. 1 is a simplified schematic diagram of a related art nox sensor. As shown in fig. 1, the automobile exhaust firstly enters a first chamber of a nitrogen-oxygen sensor, and a reaction including at least one of the following formulas (1) to (3) is performed in the first chamber by using a first pump electrode in the first chamber:
4HC+5O2→2H2O+4CO2 (1)
2CO+O2→2CO2 (2)
2H2+O2→2H2O (3)
for HC, CO and H in tail gas2The substances are captured and oxidized to generate H2O and/or CO2. Wherein, the first chamber can utilize the oxygen conducting capacity of the solid electrolyte to manufacture the oxygen environment with balanced inside and outside the chamber, and when the gas in the first chamber is in an oxygen-deficient state, under the action of the first pump electrode and the external electrode of the first chamber, the oxygen ion O is used2-In a manner to conduct oxygen from the outside air into the first chamber.
The tail gas is pretreated by the first chamber and then enters the second chamber, and mainly comprises H2O、CO2And nitrogen oxide, and more than 90% of the nitrogen oxide is NO, so that the second chamber utilizes the second pump electrode, and the reaction of the following formula (4) is performed in the second chamber:
2NO→N2+O2 (4)
catalytic reductive decomposition of NO to N2And O2And in the second chamberO of (A) to (B)2Content of O in the outside air2The difference in the contents can be known from the "oxygen flow" voltage developed across the solid electrolyte between the second chamber and the outside, and therefore, from the measured "oxygen flow" voltage and the known O in the outside air2Content, i.e. the O in the second chamber2And (4) content.
The first pump electrode of the first chamber of the current nitrogen-oxygen sensor usually adopts a Pt electrode, namely a platinum electrode, wherein the platinum is an inert noble metal, does not participate in electrode reaction per se, and has good oxidation-reduction catalysis effect under the condition of electrification. When the power is supplied, the Pt electrode can be used for HC, CO and H2Etc. can also reduce NO, but HC, CO, H2It is easier for NO to be trapped by Pt, so the Pt electrode in the first chamber can catalyze HC, CO, H first2Oxidation occurs and most of the NO is "let through" into the second chamber.
Nevertheless, a small amount of NO in the exhaust gas is inevitably reduced and decomposed by the Pt electrode in the first chamber by mistake, so that the total amount of NO entering the second chamber is less than the total amount of NO in the actual exhaust gas, and the measurement of the amount of NO emission is inaccurate.
In view of the analysis of the applicant on the above problems, the invention provides a nitrogen-oxygen sensor, a nitrogen oxide measurement method and a vehicle, so that the pretreatment in the first chamber can reduce the false consumption of NO as much as possible, the total amount of NO entering the second chamber is closer to the total amount of NO in actual tail gas, and the measurement accuracy of the NO emission is further improved.
In addition, the nitrogen-oxygen sensor mentioned in the embodiment of the invention is a nitrogen oxide measuring device in an exhaust gas after-treatment system of an automobile, and is used for measuring nitrogen oxide NO in exhaust gas finally discharged by the automobileXMonitoring the discharge amount; the pump electrodes including the first pump electrode and the second pump electrode mentioned in the embodiments of the present invention are electrodes inside the nitrogen-oxygen sensor chamber, and are respectively communicated with an external electrode to form a loop, and have the functions of pumping oxygen and catalyzing oxidation reduction.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a nitrogen oxygen sensor according to an embodiment of the present invention. As shown in fig. 2, an embodiment of the present invention provides a nitrogen oxide sensor, including: a first chamber, a second chamber;
the first chamber is provided with a first pump electrode which is a Pt-Au composite electrode used for catalyzing HC, CO and H2(ii) at least one species of (a);
the second chamber is used for catalyzing NO reaction and obtaining the discharge amount of NO.
As shown in fig. 2, in the embodiment of the present invention, the first chamber is communicated with the second chamber, and the vehicle exhaust firstly enters the first chamber, is pretreated by the first chamber, and then enters the second chamber.
Wherein, the nitrogen oxygen sensor can be arranged at different positions in an automobile exhaust aftertreatment system according to actual requirements. If the nitrogen-oxygen sensor is arranged at the rear section of the automobile aftertreatment system, for example, behind the SCR device, the automobile exhaust is the automobile exhaust treated by the aftertreatment system, and the final emission of nitrogen oxides of the automobile can be measured, so that the emission condition of the nitrogen oxides of the automobile can be known; if the nitrogen-oxygen sensor is arranged at the front section of the automobile aftertreatment system, the automobile exhaust is engine exhaust which is not treated by the aftertreatment system, and the nitrogen oxide emission of the automobile engine can be measured, so that the characteristics and the combustion condition of the engine can be known.
As shown in fig. 2, the first pump electrode is connected to the power supply together with the common electrode outside the chamber to form a communication circuit, and when the first pump electrode is energized, the first chamber performs a reaction including at least one of the formulas (1) to (3) above, and the reaction proceeds with respect to HC, CO, H in the exhaust gas2Is captured and oxidized to generate H2O and/or CO2。
The Pt-Au composite electrode comprises a Pt material and an Au material which can be in direct contact with tail gas at the same time, namely a platinum material and a gold material.
In this example, the Au pairs HC, CO, H in the Pt-Au composite electrode2And the Pt in the Pt-Au composite electrode catalyzes oxygen elements to obtain electrons.
Among them, Au has a strong catalytic ability against a specific substance in addition to its capturing ability. And Pt has certain catalytic capability and originally has certain trapping capability.
First, gold has strong capturing ability and catalytic cracking ability with respect to a substance containing hydrogen element "H", and thus, gold "Au" in the Pt-Au composite electrode captures HC and H2It is then also possible to catalyze the oxidation of HC to H together with platinum "Pt2O and CO2H is prepared by2Catalytic oxidation to H2And O. Secondly, the capture capacity of gold to CO is far superior to that of NO, CO is captured at Au, and CO is catalytically oxidized into CO mainly by Pt2. Therefore, the Pt-Au composite electrode can realize good matching and is suitable for HC, CO and H2Is efficiently trapped and catalyzed without substantially catalyzing the NO reaction.
In this embodiment, a solid electrolyte is used to connect oxygen inside and outside the chamber, and the oxygen is transported between the inside and outside of the chamber in cooperation with the first pump electrode and the second pump electrode in the energized state. Specifically, when the exhaust gas enters the first chamber region, if the exhaust gas is in an oxygen-rich state, the first pump electrode catalyzes oxygen and HC, CO, H in the exhaust gas2React to form H2O、CO2(ii) a If the tail gas is in a lean oxygen state, the solid electrolyte has the balance capacity for the oxygen concentration at the inner side and the outer side of the chamber, oxygen can be automatically transported into the first chamber through the solid electrolyte, and the first pump electrode catalyzes the oxygen and HC, CO and H2React to form H2O、CO2。
Further, the exhaust gas can be judged to be in an oxygen-rich state under the condition that the air-fuel ratio is greater than 14.3: 1; and under the condition that the air-fuel ratio is less than or equal to 14.3:1, judging the tail gas to be in an oxygen-poor state.
In addition, in this embodiment, first pump electrode connects the power negative pole, and when oxygen was surplus in first cavity, can accelerate oxygen and pass through solid electrolyte to the outside transportation of first cavity, makes the oxygen content balance in the first cavity, and can not cause the unnecessary fluctuation of oxygen content in the second cavity, avoids influencing the measurement of the emission of nitrogen oxide.
Referring to fig. 3, fig. 3 is a schematic diagram illustrating an operation of oxygen transportation according to an embodiment of the present invention. As shown in fig. 3, the Pt particles constituting the pump electrode in the region a donate electrons to oxygen, and the reaction of the following formula (5) occurs:
O2+4e→2O2- (5)
generating oxygen ions;
then, the solid electrolyte with oxygen ion conduction capability transports oxygen ions to the pump electrode in the area B, the Pt particles forming the pump electrode in the area A carry away electrons of the oxygen ions, and the reaction of the following formula (6) occurs:
2O2--4e→O2 (5)
generating oxygen;
conduction of oxygen from the a region to the B region is completed.
In this embodiment, the region a may be the interior of the first chamber and the region B may be the exterior of the second chamber.
In this embodiment, the reaction of formula (4) above to produce N can be catalyzed by NO in the second chamber2And O2Then measuring O again2And further calculating the amount of NO emission.
Referring to fig. 4, fig. 4 is a schematic cross-sectional view of a Pt-Au composite electrode according to an embodiment of the present invention. In one embodiment, as shown in FIG. 4 in conjunction with the above examples, the Pt-Au composite electrode is composed of Pt particles and Au particles distributed alternately, and the Pt particles and the Au particles together complete HC, CO, H2Capture and oxidation of at least one substance in (1).
Further, as shown in FIG. 4, the Pt particles and Au particles in the Pt-Au composite electrode can be uniformly distributed on the solid electrolyte, so that the Au particle pair HC, CO, H2At leastAfter a substance is captured, the Pt particles adjacent to the Au particles can oxidize the substance captured by the Au particles, optimal capture and oxidation cooperation is realized, consumption of NO in the first cavity is reduced better, and the measurement accuracy of NO emission is improved.
For HC, CO and H in tail gas2The capture and oxidation proceeds, and relatively speaking, the Au particles that are used primarily for capture are smaller than the Pt particles that are used primarily for oxidation of these species, because catalytic oxidation of these species requires a larger surface contact area with the exhaust.
To further achieve a working fit between the Pt and Au particles while meeting the economics of material use, in one embodiment, the Pt particles are 5-10 microns in diameter and the Au particles are 0.1-1 micron in diameter.
In combination with the above embodiments, the pair of HC, CO, H is enhanced by the first chamber2The ability to capture and catalyze the reaction greatly reduces the false consumption of NO, and therefore the amount of NO emitted from the second chamber is more accurate.
In one implementation, the measuring the discharge amount of NO in the second chamber according to the embodiment of the present invention specifically includes:
the second chamber is provided with a second pump electrode and a voltage sensor; the second pump electrode is used for catalyzing NO reaction, and the voltage sensor obtains the NO emission amount by detecting the difference between the oxygen content of the second chamber and the oxygen content of the outside air.
Preferably, the second pump electrode may employ a Pt electrode composed of uniformly dispersed Pt particles.
As shown in fig. 2, the second pump electrode is connected to a power supply together with a common electrode outside the second chamber to form a communication circuit. Wherein the second pump electrode is connected with the negative electrode of the power supply.
The voltage sensor measures a potential difference between the second pump electrode and the reference electrode, and the change of the potential difference corresponds to the change of the difference value between the oxygen content inside the second chamber and the oxygen content in the outside air.
Go toStep (b), according to the variation of the potential difference and an empirical formula, the newly added O in the second chamber can be calculated2Amount according to the addition of O2And the amount of NO discharged can be obtained.
In addition, as shown in fig. 2, in one embodiment, in order to ensure that the resistance value of the solid electrolyte changes linearly, a heating electrode may be further disposed in the nitrogen-oxygen sensor, and a fixed temperature value may be set according to the electrical characteristics of the solid electrolyte, so that the resistance value of the solid electrolyte is maintained at the fixed temperature value to maintain the linear change of the resistance value of the solid electrolyte.
For example, the fixed temperature value may be set to 560 ℃ for a solid electrolyte.
Wherein the solid electrolyte may be zirconium oxide ZrO2Adding Y as main material2O3Or a mixture of CaO. Y is2O3And CaO can improve the concentration of oxygen ion vacancies and can also enable ZrO to be ZrO2In the form of a cube or a cuboid at low temperature to form zirconium oxide ZrO2The crystal cell has larger gaps, so that oxygen ions are unobstructed in the gaps, and the conductivity and the oxygen ion flow rate of the crystal cell are improved. Wherein, Y2O3Or the volume fraction of CaO may be set to 7% to 10%, further, may be 8%.
In this embodiment, the nitrogen oxygen sensor provided by the invention can achieve the following beneficial effects:
the beneficial effects are that: before the nitrogen-oxygen sensor measures the discharge amount of nitrogen oxides, the Pt-Au composite electrode is used in advance to measure other substances possibly influencing the measurement of the nitrogen oxides in the automobile exhaust, including HC, CO and H2And the Pt-Au composite electrode has capture capacity far exceeding that of NO for substances containing H and CO, so that the consumption of NO in the pretreatment process is reduced, the influence on the measurement of nitrogen oxide is further reduced, and the accuracy of the measurement of the nitrogen oxide is improved.
The beneficial effects are that: Pt-Au complex for pretreating other substances possibly influencing nitrogen oxide measurement in nitrogen oxygen sensorThe combined electrode adopts the design of Pt particles and Au particles which are distributed in a staggered way, and the adjacent Pt particles and Au particles are matched for HC, CO and H2And the capture and catalytic oxidation of substances and the like realize a better pretreatment effect, further reduce the consumption of NO in the pretreatment process and improve the accuracy of the final measurement of the nitrogen oxide.
Referring to fig. 5, fig. 5 is a flowchart illustrating steps of a method for measuring nitrogen oxides according to an embodiment of the present invention. As shown in fig. 5, an embodiment of the present invention further provides a method for measuring nitrogen oxides, which is applied to the nitrogen oxide sensor described in any of the above embodiments, where the method specifically includes:
in the process that the automobile exhaust is sequentially discharged into the first chamber and the second chamber of the nitrogen-oxygen sensor,
s31, HC, CO and H contained in the automobile exhaust2Is adsorbed by the Pt-Au composite electrode and is oxidized into H in the first chamber2O and/or CO2；
Wherein, the first pump electrode and the common electrode outside the chamber are connected with the power supply together to form a communicating circuit, and when the first pump electrode is electrified, the first chamber performs reaction comprising at least one formula from (1) to (3) above, and HC, CO and H in the tail gas are reacted2Is captured and oxidized to generate H2O and/or CO2。
S32, reducing NO in the automobile exhaust to N in the second chamber2And O2；
Wherein NO can be catalyzed in the second chamber to perform the reaction of the above formula (4) to produce N2And O2。
S33, according to the O2The resulting oxygen flow voltage, in combination with the reference voltage, yields the NO emission.
Optionally, Au in the Pt-Au composite electrode is used for HC, CO and H2And the Pt in the Pt-Au composite electrode catalyzes oxygen elements to obtain electrons.
Optionally, the Pt-Au composite electrode is formed by interleavingDistributed Pt and Au particles that together complete HC, CO, H2Capture and oxidation of at least one substance in (1).
Optionally, the second pump electrode in the second chamber catalyzes the reduction of NO to N2And O2And the voltage sensor in the second chamber detects the difference change of the oxygen content between the second chamber and the outside air to obtain the NO emission.
Specifically, oxygen O generated in the above step2An oxygen flowing voltage is formed between the second pump electrode in the second chamber and the reference electrode outside the second chamber, so that the indication value of the voltage sensor is changed, and O is measured2And further converting the amount of the produced NO to obtain the amount of the discharged NO.
For example, originally, under the condition of oxygen balance inside and outside the second chamber, the indication value of the voltage sensor is 0.45V, and due to the generation of the reverse oxygen flowing voltage, the indication value of the voltage sensor becomes 0.44V, and then according to the indication value change, the corresponding O can be obtained according to an empirical formula or a corresponding relation table measured in advance2And further converting the amount of the produced NO to obtain the amount of the discharged NO.
In one embodiment, the O generated by the cracking of NO in the second chamber can also be calculated using a current sensor to measure the oxygen current2And further obtaining the NO emission.
The embodiment of the invention also provides a vehicle, which specifically comprises: a nitrogen oxygen sensor as in any preceding embodiment.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A nitrogen oxygen sensor, comprising: a first chamber, a second chamber;
the first chamber is provided with a first pump electrodeThe electrode is a Pt-Au composite electrode which is used for catalyzing HC, CO and H2At least one substance of (a);
the second chamber is used for catalyzing NO reaction and obtaining the discharge amount of NO.
2. The NOx sensor of claim 1 wherein the Au in the Pt-Au composite electrode is coupled to HC, CO, H2And the Pt in the Pt-Au composite electrode catalyzes oxygen elements to obtain electrons.
3. The NOx sensor as recited in claim 1, wherein the Pt-Au composite electrode is composed of Pt particles and Au particles which are distributed in a staggered manner, and the Pt particles and the Au particles jointly complete HC, CO and H2Capture and oxidation of at least one substance in (1).
4. The nitroxide sensor of claim 3, wherein the Pt particles are 5-10 microns in diameter and the Au particles are 0.1-1 microns in diameter.
5. The nitroxide sensor of claim 1, wherein the second chamber is provided with a second pump electrode and a voltage sensor; the second pump electrode is used for catalyzing NO reaction, and the voltage sensor obtains the NO emission amount by detecting the difference between the oxygen content of the second chamber and the oxygen content of the outside air.
6. A method for measuring nitrogen oxides, which is applied to the nitrogen oxide sensor according to any one of claims 1 to 5, the method comprising:
in the process that the automobile exhaust is sequentially discharged into the first chamber and the second chamber of the nitrogen-oxygen sensor,
HC, CO and H contained in the automobile exhaust2Is adsorbed by the Pt-Au composite electrode and is oxidized into H in the first chamber2O and/or CO2；
NO in the automobile exhaust is reduced into N in the second cavity2And O2；
According to the O2The resulting oxygen flow voltage, in combination with the reference voltage, yields the NO emission.
7. The method of claim 6, wherein the Au pairs in the Pt-Au composite electrode are HC, CO, H2And the Pt in the Pt-Au composite electrode catalyzes oxygen elements to obtain electrons.
8. The method of claim 6, wherein the Pt-Au composite electrode is composed of Pt particles and Au particles distributed in an alternating manner, and the Pt particles and the Au particles jointly complete HC, CO, H2Capture and oxidation of at least one substance in (1).
9. The method of claim 6, wherein the second pump electrode in the second chamber catalyzes the reduction of NO to N2And O2And the voltage sensor in the second chamber detects the difference change of the oxygen content between the second chamber and the outside air to obtain the NO emission.
10. A vehicle characterized in that an aftertreatment system of the vehicle comprises a nitrogen oxide sensor according to any one of claims 1 to 5.
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