CN2549466Y - Ion exchange membrance conductivity tester - Google Patents

Abstract

The utility model relates to an ion exchange membrane conductivity tester. A four-electrode system is adopted; the two ends of the tested membrane are respectively positioned in two electrolytic cells holding electrolyte so as to form a series circuit; current is provided to the membrane through the electrolyte; a voltage following circuit tests the voltages of two certain points in the membrane; a function recorder records the voltage and the current; the electric conductivity is gained through the law of ohm. The utility model has the advantages of eliminating a plurality of factors that influence the testing result, reducing the error, improving the reliability of testing, having simple instrument and being easy to be realized.

Description

A kind of measurement mechanism of ion exchanging film conductivity

Technical field

The utility model relates to a kind of mensuration of fuel cell intermediate ion exchange membrane conductivity.

Background technology

It is first-selected clean, generation technology efficiently of 21 century that fuel cell is identified as, and the research and development of fuel cell technology is the attention of national governments and major company extremely

Amberplex is the critical component of fuel cell, and its performance directly influences the quality of battery.Have only the conductivity of amberplex is accurately measured, could estimate the performance of its film objectively, necessary scientific basis could be provided for physics one chemical process of furtheing investigate its conduction.

Amberplex is different from conductor and general electrolyte, and it is a kind of solid electrolyte.In electric field, conductor is to move and conduct electricity by electronics, have negative ions to move in opposite directions in the electrolyte and conduct electricity, and PEM can think that negative ion does not move, and has only moving of proton and conducts electricity.Therefore when studying and measuring its electric conductivity, just can not apply mechanically simply conductor and electrolytical research measuring method, must take into full account circuit and electrode is conductor, they are to move and go into electric current by electronics, and film is to move and go into electric current by proton, at electrode and film touching position is two kinds of different electrically conducting manners, the existing electrochemical reaction in its interface produces, electric charge accumulation is arranged again, can produce certain auxiliary voltage, if do not get rid of the influence of this voltage, can bring gross error to measurement, even mistake.

As far back as the sixties in 20th century GE to develop with the amberplex be the fuel cell of the PEM of barrier film.And to the conductance measurement of amberplex also with regard to corresponding expansion, the research report about the electric conductivity of amberplex has been arranged much successively.As: " Electropolymer Studies, II " 12 phases of nineteen sixty-eight, 115 volumes, the 1264-1270 page or leaf is to " polystyrolsulfon acid exchange membrane Electrical Conductivity ".Its method is to use the DC dump method, it mainly is the discharge volt-ampere curve of recording film, adopt this method can produce error, the main cause that produces error has the migration of ion in galvanic polarization, the film to cause the variation of ion concentration and the time response of discharge volt-ampere curve etc., and this method is measured more coarse.And for example: " The Journal of Physical Chemistry " o. 11th 98 volume 2936-2940 pages or leaves in 1994, reported " Study on AC impedance of polyimide ionic conduction ", its method is the alternating current that adds various frequencies to film, draw impedance complex plane figure, the intersection point of semicircle and real axis is tried to achieve resistance from figure, calculate conductivity again, measure conductivity with this method, the main cause that produces error has: the migration of ion causes the variation of ion concentration in low frequency electricity direct current polarization and the film, circuit model is too simplified during high frequency, and the influence of telegraph circuit is serious." Journal of Electroanaly Chemistry " nineteen ninety-fives 395 are rolled up the 67-73 page or leaf for another example, reported " measuring the conductivity of film with the coaxial probe openend ", its method is to compress film with the coaxial probe openend, utilize film the emission differences of microwave to be come the conductivity of analytical calculation film, the main cause that this method produces error has: the degree of tightness that probe contact with film causes the variation of film thickness, microwave by film the crack leakage and penetrate etc.

Summary of the invention

The purpose of this utility model be at ion concentration in polarization that occurs in the above-mentioned measuring method and the film reduce cause deficiency of measurement etc., and provide a kind of measurement mechanism simply accurately, eliminate the influence of these factors, reduce systematic error and accidental error, improve measuring accuracy, and can accurately measure the conductivity of amberplex.It is simple, easy to operate that this system has an instrument, accurately measures the amberplex electric conductivity.

Because electrode is different materials with film, its electrical conduction mechanism is different, and film is in measuring process, because effect of electric field, ion in the film constantly moves, ion is moved to electrode surface and electrode and is reacted or be deposited in electrode surface, and As time goes on, the quantity that ion moves away is more and more, the quantity of ion is also just fewer and feweri in the film, the variation of ion concentration will cause the variation of conductivity in the film, will certainly produce than mistake.

The utility model adopts four electrode systems, its objective is potential electrode and working electrode are separated, and reduces the electric current on the potential electrode, thereby reduces the polarization on the potential electrode, makes that measurement is more accurate.

The concrete measuring method of the utility model is: the amberplex two ends are placed two electrolytic cells, make electrolyte and amberplex form the circuit of connecting, under effect of electric field, allow current source provide electric current to film by electrolytic solution, ion in the electrolyte can enter in the amberplex like this, replenish the loss of ion in the amberplex, the interior ion degree of depth of film can not dwindled rapidly, the interior ion of stabilising membrane.On measuring film, adopt voltage compensating method during certain two point voltage, pass through voltage compensation, can make that electric current is zero on the potential electrode, reach the influence of the polarizing voltage on the thorough elimination potential electrode, compensating circuit is by voltage source, voltage follower, voltage comparator and oscillograph are formed, reconcile the output voltage of voltage source, making in time slowly increases, while is by the voltage waveform of comparer point under the oscillograph recording, when voltage waveform on the oscillograph takes place when opposite, this moment is because voltage compensation, do not have electric current to flow through on the potential electrode, avoided the influence of polarizing voltage dexterously, thereby reach the purpose of voltage compensation, adopt compensation method to measure the voltage of film, electric current (note voltage and current by function recording instrument, try to achieve conductivity) by Ohm law.

The utility model allows current source provide electric current by electrolytic solution to film by the two ends of film are placed in the electrolytic cell that fills electrolytic solution.Ion in the electrolytic solution is entered in the film,, make that ion concentration can not reduce rapidly in the film, overcome the variation of ion concentration in the film dexterously and the error that causes so that ion concentration can obtain certain replenishing in the film.

The utility model device, connect at the two ends of current source 1 add stream electrode 5, and be placed in the electrolytic cell 3 respectively, electrolytic cell 3 is fixed on that amberplex 4 to be measured lies in the two ends of support 2 respectively and places electrolytic cell 3 on the insulating support 2, make electrolytic solution and film to be measured constitute the circuit of connect, voltage follower 7, comparer 8, voltage source 9, oscillograph 10 formations one compensating circuit.

Description of drawings

Fig. 1: the structural representation of the utility model measurement mechanism.

Current source 1, insulating support 2, electrolytic cell 3, amberplex to be measured 4, add stream electrode 5, potential electrode 6, voltage follower 7, voltage comparator 8, voltage source 9, oscillograph 10.

Embodiment

The utility model will further be illustrated by instantiation and accompanying drawing.

Measuring method of the present utility model is: cutting out a width is D, and thickness is d, and the amberplex 4 of certain-length lies on the support 2, and its two ends place two electrolytic cells 3, makes electrode 5 constitute the circuit 3 of connecting by electrolytic cell and film to be measured.Current source 1 provides suitable electric current I by battery and film 4, and potential electrode 6 is pressed on 1 film to be measured 4, and through voltage follower, comparer 8 constitutes a voltage compensating circuit with voltage source 9 oscillographs 10.The voltage of adjusting voltage source 9 increases its voltage lentamente, is noted the voltage waveform of comparer point i simultaneously by oscillograph 10, when voltage waveform on the oscillograph 10 takes place when anti-phase, writes down the voltage U of voltage 9, gets resistance by Ohm law and is $R=\frac{U}{L}$

The conductivity of film $\mathrm{\σ}=\frac{L}{R\·S}=\frac{I\·L}{U\·d\·D}$

The conductivity measurement of the PEM Nafion117 that produces with state E.I.Du Pont Company is an example, and this film thickness is 0.183mm, and its concrete measuring method is:

Width of cutting is 10mm, is about the film into 10cm, lies on the support 2.Place the electrolytic cell 3 of the sulfuric acid solution of 1M concentration, potential electrode 6 to be pressed at the two ends of film at a distance of being the film surface of 5cm.Adjust size of current, record film 4 from the function oscillograph, the voltage that electrode is 6 is 3.1 volts, and electric current is 1.0 milliamperes in the film 4.

Get conductivity by formula $\mathrm{\σ}=\frac{1.0\×5\×{10}^{-3}}{3.1\×0.0183\×1.0}=0.088\left({S\·\mathrm{cm}}^{-1}\right)$

Claims (1)

1. the measurement mechanism of an ion exchanging film conductivity, it is characterized in that adopting four-probe measurement, connect at the two ends of current source (1) add stream electrode (5), and be placed in the electrolytic cell (3) respectively, electrolytic cell (3) is fixed on the insulating support (2), amberplex to be measured (4) lie in support (2) above, two ends also place electrolytic cell (3), make electrolytic solution and film to be measured constitute the circuit of connect, voltage follower (7), comparer (8), voltage source (9), oscillograph (10) formation one compensating circuit.