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4 Electrochemical method for thin-film covered batteries
4.
When the gas flows through the measurement chamber equipped with the galvanic cell (fuel cell) at a constant rate, the oxygen molecules in the gas diffuse through the polymer film covered on the galvanic cell surface, and a reduction reaction occurs at the cathode made of inactive metal.
O 2 + 2H 2 O + 4C = 4OH -
While the anode is lead gelled aqueous KOH etching occurs in the oxidation reaction of the electrolyte, the electronic circuit outputs outwardly: 2OH - + = Pb of PbO + H 2 O + 2E
2Pb+O 2 =2PbO
The current of the external circuit is proportional to the partial pressure of oxygen in the gas, that is, when the total paw is constant, the current is proportional to the concentration of oxygen in the gas
4.
4.
Nitrogen or argon : the purity is not less than 99.
Oxygen: The purity is not less than 99.
4.
4.
4.
4.
4.
4.
4.
4.
4.
4 Sampling
The sampling procedure is the same as 3.
4, and the electrochemical method of film-covered battery can be used for on-site detection
.
4.
5 Measurement procedure
4.
5.
1 Instrument assembly
Connect the sample or standard gas source, the flow regulating valve, and the oxygen meter in turn.
The connecting pipelines are all stainless steel pipes.
The outlet of the oxygen meter is connected to a 50cm long and 3mm inner diameter stainless steel pipe, and then connected to the flowmeter in an appropriate manner
.
4.
5.
2 Instrument flow chart (see Figure 3)
Figure 3 Flow chart of oxygen measuring instrument
4.
5.
3 Inspection of measuring device
Before the formal measurement, the connecting pipelines and joints should be checked for leaks
.
Increase the gas flow rate to twice the gas flow rate used in the formal measurement, and no obvious changes should be observed in the reading of the oxygen meter, otherwise it indicates that the measurement device is leaking
.
4.
5.
4 Calibration
Calibrate the instrument with the atmosphere or a standard gas with appropriate oxygen content according to the instrument's instruction manual.
The flow rate of the atmosphere or standard gas should be consistent with the gas flow rate used when measuring the sample
.
4.
5.
5 Sample determination
Assemble the instrument as described in 4.
5.
1, prepare the instrument and adjust the working parameters according to the instructions for use of the instrument
.
Introduce the gaseous sample at a given flow rate.
The flow rate of the sample gas should be such that the oxygen meter can obtain a stable reading.
The reading stabilization time is not less than 2min
.
In order to keep the instrument in good working condition, a nitrogen stream humidified by a mixer is regularly used to flow through the measuring cell at a flow rate of 1L/h to 2L/h to maintain the water in the gel electrolyte of the primary battery
.
Before and after the measurement, the measurement chamber was flushed with high-purity nitrogen at a lower flow rate
.
4.
6 Presentation of results
The oxygen content in the sample is expressed as the arithmetic mean of the two repeated measurements, rounded to the nearest 1mL/m in accordance with GB/T8170
.
4.
7 Repeatability limit
In the same laboratory, the difference between the two independent test results obtained by the same operator using the same equipment, using the same test method, and independently testing the same object under test within a short period of time should not exceed the repetition of Table 3.
Repetitive limit (r), exceeding the repeatability limit (r) does not exceed 5%
.
Table 3 The repeatability of the electrochemical method for measuring the oxygen content of the sample in the film covered battery
5 reports
The report should include the following:
a) All information required for the sample, such as sample name, batch number, sampling location, sampling date, sampling time, etc.
;
b) The number of this standard;
c) The oxygen content in the standard sample;
d) Measurement results;
e) The name of the analyst and the date of analysis, etc.
;
f) A detailed record of any abnormalities observed during the measurement
.
Related Links: Determination of Oxygen in Gas Phase on Industrial Butadiene Liquid (2)