A Simple Oxygen Detector Using Zinc−Air BatteryYoong Kin Hooi, Masayoshi Nakano, and Nobuyoshi Koga*

Department of Science Education, Graduate School of Education, Hiroshima University, 1-1-1 Kagamiyama, Higashi-Hiroshima739-8524, Japan

*S Supporting Information

ABSTRACT: The construction of a simple oxygen detector using a zinc−air battery as anoxygen sensor is described. It is a user-friendly device that can be employed in variouslaboratory activities in both junior and senior high schools. A short circuit can beintroduced to reduce the O2 concentration in the air-diffuser layer of the battery that causesa decrease in the voltage. This phenomenon provides the basis to make an electrical devicethat can produce a voltage increase whenever oxygen gas is present. If the surroundings donot contain any available oxygen gas, the voltage in the zinc−air battery would remainstatic. In addition, time-to-operate of an electric component attached to the battery can alsobe used for semiquantitative determination of O2 concentration in a gas sample.

KEYWORDS: Elementary/Middle School Science, High School/Introductory Chemistry, Demonstrations,Hands-On Learning/Manipulatives, Gases, Laboratory Equipment/Apparatus

The detection and identification of O2 are commonlaboratory activities, which are introduced to students as

early as elementary school. A flame test, in the form ofrelighting of glowing splinter, acts as a common and basicqualitative test for students to confirm the presence of O2. At ahigh-school level, a solution containing indigo carmine can beused to indicate the presence of O2. A semiquantitativemeasurement of O2 concentration can be performed using a gasdetector tube.1 The measurement of O2 concentration using anelectric sensor with a data logger is currently being introducedin school laboratories. This paper describes a new and simplemethod to qualitatively detect the presence of O2 andsemiquantitatively measure the concentration.Commercially available zinc−air batteries have been used in

various experiments in high schools.2−4 The zinc−air batteryworks in such a way that oxygen gas becomes the activecathode, while zinc is the anode contained within the battery.The respective electrode reactions of the zinc−air battery andthe corresponding standard potentials of the equations aswritten are5

− + → + +

° =

− −l

E

( )Zn(s) 2OH (aq) ZnO(s) H O( ) 2e

( 1.25 V)2

(1)

+ + + →

° =

− −l

E

( )O (g) 2H O( ) 4e 4OH (aq)

( 0.4 V)2 2

(2)

The overall reaction of the battery is

+ → ° =E2Zn(s) O (g) 2ZnO(s) ( 1.65 V)2 (3)

According to eq 3, the battery consumes atmospheric O2 andgains mass in the form of ZnO. Therefore, Faraday’s law can beconfirmed by measuring the change in the volume of O2

consumed or the gained mass of the zinc−air battery withincreasing quantity of electricity in a circuit using the zinc−airbattery as the power source.2−4 At the operating voltage of thezinc−air battery (1.4 V), the electric current in a circuit, with asmall resistance, linearly changes with respect to theatmospheric O2 concentration.

5 This makes it possible to usethe zinc−air battery as a sensor for measuring O2

concentration. This idea is further developed by applying anequivalent circuit in a device.6

In this communication, we report a method to use a zinc−airbattery in a very simple circuit for detecting O2 andsemiquantitatively determining the concentration. With a verysmall residual O2 concentration in the air-diffuser layer of thezinc−air battery, the electromotive force of eq 3 dramaticallydecreases.7 The re-establishment of the electromotive force byexposure to O2 from a gas sample provides evidence for thepresence of O2, and the recovery time is an approximatemeasure of the O2 concentration in the sample. The basicprinciple is described in the Supporting Information.

■ DETECTOR SETUP

A simple handmade detector was constructed using a zinc−airbattery (1.4 V Panasonic PR44 or 1.4 V Panasonic PR2330),rubber stoppers (size 2, 3, and 8), a glass tube, wires, a switch,and an electronic melody box P70−3934 (Narika, Japan).

Communication

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© XXXX American Chemical Society andDivision of Chemical Education, Inc. A dx.doi.org/10.1021/ed400169z | J. Chem. Educ. XXXX, XXX, XXX−XXX

There are several air holes in these models of the zinc−airbatteries. Leaving one hole open for gas sample intake, otherholes were sealed with a transparent tape. Then the zinc−airbattery was fitted to a shaped rubber stopper. This was done toreduce the rate of voltage increase by slowing the oxygen gasadsorption in the air-diffuser layer of the zinc−air battery. It isimportant, particularly after short circuit, to provide ample timefor the voltage hike to be detected by the electrical component;in this case, an electronic melody box. The detector wasconstructed with a switch acting as an alternative circuit pathfor the short circuit, as can be seen in Figure 1.

■ APPLICATION IN SCHOOL LABORATORIES

Short Circuit and Detector Performance

When a new zinc−air battery is first exposed to the atmosphericair, the voltage gradually rises and subsequently remainsconstant at around 1.4 V. The idea was to reduce the voltageto a value lower than the minimum requirement of the melodybox, which, in this case, was 0.760 V. By implementing the ideaof using a short circuit, the negative and the positive terminalswere connected to cause a voltage drop. By connecting thebattery to a voltmeter, the voltage immediately after the short-circuit treatment (initial voltage) was investigated. When aPR44 battery was tested, the voltage dropped to ca. 0.2 V after ashort-circuit time of 30 s (Figure 2). When a PR2330 batterywas tested, the voltage dropped to ca. 0.5 V with a short-circuittime of 30 s and resulted in an air-charging time of 30 min ormore, and a 15 s short−circuit time resulted in an air charging-time of less than 30 min. A maximum voltage differencebetween the minimum requirement of the melody box and thevoltage immediately after completing the short-circuit treat-ment of the battery gives optimum results for the qualitativeand semiquantitative tests. The relationship between the O2concentration in the test gas and time-to-sound using the PR44battery detector is shown in Figure 3. The time-to-sound valuesat the respective O2 concentrations are reproducible. Therelation between O2 concentration and time-to-sound can beempirically expressed by an inverse proportion. This relationwas used as a calibration curve to determine the O2concentration in a test gas.Electrolysis of Water

Two detectors, similar to those shown in Figure 1, wereemployed to verify the gas sample evolved from the electrolysisof water while being wired to a voltmeter instead of the melody

box, to investigate the voltage change (Figure 4). When twomelody boxes were wired to the oxygen detector at each

electrode instead of the voltmeters, the melody box at anodeproduced sound after 2 min, but no sound at cathode for morethan 5 min. The audio results can be explained by the voltagechanges at each electrode shown in Figure 4 and the lineshowing the minimum voltage requirement of the melody box.

Figure 1. (Bottom) A completed detector and (top) thecorresponding circuit diagram.

Figure 2. Relationship between duration time of the short-circuittreatment and the voltage recorded immediately after completing theshort-circuit treatment (initial voltage) for the PR44 zinc−air battery.SW is the switch and V is the voltmeter.

Figure 3. A calibration curve for the semiquantitative determination ofO2 concentration using the PR44 battery detector setup.

Figure 4. Voltage change at the anode and cathode in detectors duringthe electrolysis of water using the PR44 battery detector setup.

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Application in Other Experiments

The performance of the oxygen detector using the zinc−airbattery in various experiments in student laboratory experi-ments is summarized in Table 1. As can be seen from these data(comparison of different gases), the detector selectively worksfor oxygen. In addition, if the initial voltage of the zinc−airbattery, after the short-circuit treatment, is set as constant ineach experimental run, the concentration of oxygen can besemiquantitatively determined by comparing the time requiredby electronic melody box to make sound. This can be observedin the results of the experiments for the human breath and thecombustion of a candle. The details of all the experiments listedin Table 1 are described in the instructor information found inthe Supporting Information.

■ CONCLUSIONThe simple device with a zinc−air battery as O2 sensor can beapplied to various student experiments at schools. Thedetection and determination of O2 concentration is morequantitative than the conventional flame test, easier to use thanan indigo carmine solution, and more cost-effective than a gasdetector tube.

■ ASSOCIATED CONTENT*S Supporting Information

Instructor information. This material is available via theInternet at http://pubs.acs.org.

■ AUTHOR INFORMATIONCorresponding Author

*E-mail: nkoga@hiroshima-u.ac.jp.

Notes

The authors declare no competing financial interest.

■ ACKNOWLEDGMENTSThe present work was supported partially by a grant-in-aid forscientific research (A)(25242015), (B)(22300272) and chal-lenging exploratory research (23650511) from Japan Societyfor the Promotion of Science. One of the authors (Y.K.H.)acknowledges the Ministry of Education, Culture, Sports,Science, and Technology in Japan for the financial support inthe Teacher Training Program.

■ REFERENCES(1) Collings, A. J. Performance Standard for Detector Tube UnitsUsed to Monitor Gases and Vapours in Working Areas. Pure Appl.Chem. 2001, 54 (9), 1763−1767.(2) Kamata, M.; Kawahara, T. Teaching Materials using Zinc−AirBatteries. I. Educational Experiment for Faraday’s Law. Kagaku toKyoiku 2000, 48 (3), 192−194.(3) Kamata, M. Teaching Materials using Zinc−Air Batteries. II.Educational Experiment for Faraday’s Law (2nd report). Kagaku toKyoiku 2000, 48 (5), 330−331.(4) Kamata, M.; Paku, M. Exploring Faraday’s Law of ElectrolysisUsing Zinc−Air Batteries with Current Regulative Diodes. J. Chem.Educ. 2007, 84 (4), 674−676.(5) Tanaka, Y.; Koga, N. A Convenient Measurement of OxygenConcentration using Zinc−Air Battery. Chem. Educ. J. 2009, 13(1),No.13-10. http://chem.sci.utsunomiya-u.ac.jp/v13n1/10_2d4_1.pdf(accessed Dec 2013).(6) Takahashi, M.; Yamauchi M. Equivalent Circuits of Zinc−AirBattery and Analysis of Zinc−Air Battery Oxygen Sensor using theEquivalent Circuits. Abstract PRiME2012, 2012, #3553. http://ma.ecsdl.org/content/MA2012-02/51/3553.full.pdf (accessed Dec 2013).(7) Smith, G. C.; Hossain, Md. M.; MacCarthy, P. Why BatteriesDeliver a Fairly Constant Voltage until Dead. J. Chem. Educ. 2012, 89(11), 1416−1420.

Table 1. Performance of the Oxygen Detector Using Zinc−Air Battery in Various Experiments

Time to Sound/min

Experiment Gases PR44a PR2330b

Water Electrolysis O2 evolved from Anode (+) 1.9 2.5H2 evolved from Cathode (−) No sound (5 min) No sound (10 min)

Comparison of Gases O2 by H2O2(aq) decomposition 0.8 ± 0.1 1.0H2 by reaction of HCl(aq) + Zn(s) No sound No soundCO2 by reaction of HCl(aq) + Na2CO3(s) No sound No soundO2 consumed from air by chemical body warmer (kairo)c No sound No sound

Human Breath Oxygen inhaler (95% O2) 0.9 ± 0.1 1.2 ± 0.2Inspiration (18.8% O2)

d 8.3 ± 0.3 9.4 ± 0.2Expiration (16.2% O2)

d 11.4 ± 0.8 11.5 ± 0.2Combustion of Candle Before (18.8% O2)

d 8.3 ± 0.3 9.9 ± 0.1After (15.1% O2)

d 11.6 ± 0.4 12.9 ± 0.1aThe initial voltage right after the short-circuit treatment is 0.2 V. bThe initial voltage right after the short-circuit treatment is 0.5 V. cSee theSupporting Information. dMeasured using an oxygen detector tube (Gastech, Japan).

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