IEC TS 62607-6-13:2020

Nanomanufacturing - Key control characteristics - Part 6-13: Graphene-based material - Oxygen functional group content: Boehm titration method

IEC TS 62607-6-13:2020 establishes a standardized method to determine the chemical key control characteristic
• oxygen functional group content on graphite oxide, graphene oxide, reduced graphene oxide and other types of functionalized graphene by
• Boehm titration method.
In this document, the measured functional groups are carboxyl groups (also in the form of their cyclic anhydrides), lactone groups, hydroxyl groups and reactive carbonyl groups. Oxygen functional groups that exhibit no reactivity such as epoxides cannot be measured
The contents of the corrigendum 1 of October 2020 have been included in this copy.

General Information

• Status: Published
• Publication Date: 27-Jul-2020
• ICS: 07.120 - Nanotechnologies
• Technical Committee: TC 113 - Nanotechnology for electrotechnical products and systems
• Drafting Committee: PT 62607-6-13 - TC 113/PT 62607-6-13
• Current Stage: PPUB - Publication issued
• Start Date: 28-Jul-2020
• Completion Date: 28-Aug-2020

Relations

• Corrected By: IEC TS 62607-6-13:2020/COR1:2020 - Corrigendum 1 - Nanomanufacturing - Key control characteristics - Part 6-13: Graphene-based material - Oxygen functional group content: Boehm titration method
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC TS 62607-6-13 ®
Edition 1.0 2020-07
TECHNICAL
SPECIFICATION
colour
inside
Nanomanufacturing – Key control characteristics –
Part 6-13: Graphene powder – Oxygen functional group content: Boehm titration
method
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IEC TS 62607-6-13 ®
Edition 1.0 2020-07
TECHNICAL
SPECIFICATION
colour
inside
Nanomanufacturing – Key control characteristics –

Part 6-13: Graphene powder – Oxygen functional group content: Boehm titration

method
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 07.120 ISBN 978-2-8322-8726-2

– 2 – IEC TS 62607-6-13:2020  IEC 2020
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, symbols and abbreviated terms . 7
3.1 Terms and definitions . 8
3.1.1 General terms . 8
3.1.2 Key control characteristics measured according to this document . 9
oxygen functional group . 9
3.1.3 Terms related to the measurement method . 9
3.2 Symbols and abbreviated terms . 9
4 General . 9
4.1 Measurement principle . 9
4.2 Sample preparation method . 10
4.3 Description of measurement equipment / apparatus . 11
4.3.1 Analytical balance, readability is 0,1 mg. . 11
4.3.2 Electric thermostatic drying oven . 11
4.3.3 Numerical control magnetic agitator/oscillator . 11
4.3.4 Automatic potentiometer, with pH electrode and accurate to 0,1 mV. . 11
4.3.5 HDPE bottles, the volume are 1 000 mL and 100 mL, with stopper. . 11
4.4 Supporting materials . 11
4.5 Ambient conditions during measurement . 11
5 Measurement procedure . 11
5.1 Detailed protocol of the measurement procedure . 11
5.1.1 Preparation of solutions . 11
5.1.2 Reactions between graphene and bases . 13
5.1.3 Instrument preparation . 13
5.1.4 Titration of the filtrate . 13
5.2 Measurement uncertainty . 14
5.3 Operation procedure, key control steps and case study . 14
6 Data analysis / interpretation of results . 14
6.1 Normalized base consumption . 14
6.2 Oxygen functional group content . 15
7 Results to be reported . 15
7.1 General . 15
7.2 Product/sample identification . 15
7.3 Test results . 15
Annex A (informative) Operation procedure and key control steps . 16
A.1 Operation procedure . 16
A.2 Key control steps . 17
Annex B (informative) Influence of CO . 18
B.1 Effect of CO on titration of base concentration . 18
B.2 Effect of CO on base consumption . 19
Annex C (informative) Lower limit of determination . 20
C.1 Experiment of lower mass of reacted sample A . 20

C.2 Determination of detection limits . 20
Annex D (informative) Test report . 23
D.1 Example of a test record . 23
D.2 Format of the test report . 23
Annex E (informative) Case study . 25
E.1 Preparation of solution . 25
E.2 Sample preparation . 25
E.3 Reactions between graphene and bases . 25
E.4 Titration of the filtrate . 26
E.5 Calculation . 28
E.6 Test report . 30
Bibliography . 31

Figure 1 – Test principle of Boehm titration . 10
Figure A.1 – Operation procedure . 16
Figure A.2 – Key control steps . 17
Figure B.1 – Titration curves of NaOH solution . 18
Figure C.1 – The normalized base consumption of different amounts of sample A . 20
Figure E 1 – Titration curves of A0 filtrate (upper left), B0 filtrate (upper right),
C0 filtrate (lower left), and D0 filtrate (lower right) . 27

Table 1 – Four types of oxygen functional group and their structures . 10
Table 2 – Reagents used in this document . 11
Table B.1 – Titration results of back titration and direct titration of NaOH solution . 19
Table B.2 – Results of base consumption of NaOH with and without bubbling N . 19
Table C.1 – Base consumption result of sample A . 21
Table C.2 – Oxygen functional group content result . 22
Table C.3 – Detection limits for different sample amounts . 22
Table D.1 – Data for calibration of titrant acid . 23
Table D.2 – Data for Boehm titration . 23
Table D.3 – Product identification (according to IEC 62565-3-1) . 24
Table D.4 – General material description (according to IEC 62565-3-1) . 24
Table D.5 – Measurement results . 24
Table E.1 – Measurement data . 27
Table E.2 – Normalized base consumption of sample 1 . 29
Table E.3 – Product identification of sample 1 . 30
Table E.4 – General material description of sample 1 . 30
Table E.5 – Measurement results of sample 1 . 30

– 4 – IEC TS 62607-6-13:2020  IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NANOMANUFACTURING – KEY CONTROL CHARACTERISTICS –

Part 6-13: Graphene powder – Oxygen functional group content:
Boehm titration method
FOREWORD
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Technical Specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 62607-6-13, which is a Technical Specification, has been prepared by IEC technical
committee 113: Nanotechnology for electrotechnical products and systems.

The text of this Technical Specification is based on the following documents:
Draft TS Report on voting
113/455/DTS 113/486/RVDTS
Full information on the voting for the approval of this Technical Specification can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 62607 series, published under the general title Nanomanufacturing –
Key control characteristics, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

– 6 – IEC TS 62607-6-13:2020  IEC 2020
INTRODUCTION
In recent years, graphene has attracted extensive attention from academia and industry, due to
the extraordinary physical and chemical properties for promising applications in energy
conversion and storage, electronics, composites and catalysis, etc. In the case of most
graphene available in the laboratory or on the market, oxygen functional groups are inevitable,
especially for the powder form products. These oxygen functionalities, which exist mainly in the
form of carboxyl groups, lactones or lactols, phenolic hydroxyl groups, reactive carbonyl groups
and epoxide groups, etc., are located on the surface or edge of the two-dimensional carbon
lattice. They affect many crucial properties of graphene, including wettability, electrical and
thermal conductivity, electron density, acidity and reactivity, etc. [1][2][3][4] , and so determine
the performance of graphene for downstream applications. For example, in an energy storage
device such as lithium ion battery or supercapacitor, the oxygen heteroatoms will introduce
irreversible reaction to exhaust the organic electrolyte and emit small molecules, which will
reduce the cycling stability and even cause safety problems to the final products [5][6]. Besides,
the oxygen functional groups will significantly decrease the electrical conductivity of graphene,
which has a negative impact on the rate capacity of the cell, due to the increase of internal
resistance for the electrode [7][8]. Furthermore, the different oxygen containing functional
groups will play very different roles in affecting the properties of graphene. For example, in
catalysis, graphene has been employed as an effective solid acid catalyst for hydrocarbon
chemistry, as many oxygen functionalities show acidic properties [9][10][11]. However, the
acidity strength of different oxygen species is distinct, as the acidity sequence is carboxyl,
lactone, hydroxyl, and carbonyl. Besides, it is proved that ketonic carbonyl groups, with higher
electron density, are the catalytic active sites for oxidative dehydrogenation reactions [12][13].
So, the type and proportion of oxygen groups will significantly influence the catalytic activity
and selectivity of graphene. Therefore, the qualification of different oxygen functional groups
on the surface of graphene is a key control characteristic for the production, application and
trading of graphene and related products.
The most common methods for identification and quantification of oxygen functional groups on
graphene are FT-IR, XPS, EELS and Boehm titration. Moreover, other recent methods such as
SAED, MS and FLOSS are springing up. However, some of these methods have difficulty
quantifying oxygen functional groups on graphene, and there is no standard method to quantify
the oxygen functional groups. Boehm titration, dating from 1962, is an efficient, repeatable and
easy to operate method with low cost. More importantly, the Boehm titration method can provide
absolute values of the surface concentration of oxygen functional groups and avoid the
ambiguity and subjectivity brought by spectroscopies, which shows its unique advantage in
quantification of many oxygen functional groups on graphene [14][15][16][17][18][19][20]. Note
that Boehm titration cannot determine the total oxygen content of a powder, as it only measures
those functional groups that can dissociate under the conditions of the test.
Boehm titration has been applied to determine the oxygen functional groups of many traditional
carbonaceous materials for decades, such as activated carbon and carbon black. In recent
years, it was applied to graphene [21][22]. Because the physical properties of graphene are
very different from those of other carbonaceous materials, the operation-specific details in this
document are suitable for powders of graphene oxide, reduced graphene oxide, graphene and
related materials only. When applying Boehm titration to graphene dispersions, the dispersion
medium needs to be removed. This document can be used as the reference for other
carbonaceous materials.
This document focuses on the determination of oxygen functional groups and standardization
of the operation method. Due to various steps such as agitation, end-point determination, etc.
required in Boehm titration, significant measurement errors can be introduced if not properly
addressed.
Numbers in square brackets refer to the Bibliography.

NANOMANUFACTURING – KEY CONTROL CHARACTERISTICS –

Part 6-13: Graphene powder – Oxygen functional group content:
Boehm titration method
1 Scope
This part of IEC TS 62607 establishes a standardized method to determine the chemical key
control characteristic
• oxygen functional group content
on graphite oxide, graphene oxide, reduced graphene oxide and other types of
functionalized graphene by
• Boehm titration method.
In this document, the measured functional groups are carboxyl groups (also in the form of their
cyclic anhydrides), lactone groups, hydroxyl groups and reactive carbonyl groups. Oxygen
functional groups that exhibit no reactivity such as epoxides cannot be measured.
The oxygen functional group content is derived by the difference between NaHCO , Na CO ,
3 2 3
NaOH and C H ONa consumption of dispersed graphene powders.
2 5
– The oxygen functional group content determined according to this document is listed as key
control characteristic in the blank detail specification for graphene IEC 62565-3-1.
– The method is applicable for graphene powder and graphene related carbon 2D materials
such as graphene oxide powder and reduced graphene oxide powder, which can be
separated from the water and ethanol by centrifugation or filtration. This document is not
applicable for sulfonate modified graphene.
– In this document, the lower limits of detection (Annex C) for carboxyl groups, lactone groups,
hydroxyl and carbonyl are 0,015 mmol/g, 0,037 mmol/g, 0,014 mmol/g, and 0,072 mmol/g,
respectively.
– This document targets graphene manufacturers and downstream users to guide their
material design, production and quality control.
2 Normative references
There are no normative references in this document.
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

– 8 – IEC TS 62607-6-13:2020  IEC 2020
3.1 Terms and definitions
3.1.1 General terms
3.1.1.1
blank detail specification
BDS
structured generic specification of the set of key control characteristics which are needed to
describe a specific nano-enabled product without assigning specific values and/or attributes
Note 1 to entry The templates defined in a blank detail specification list the key control characteristics for the nano-
enabled material or product without assigning specific values to it.
Note 2 to entry Examples of nano-enabled products are: nanomaterials, nanocomposites and nano-subassemblies.
Note 3 to entry Blank detail specifications are intended to be used by industrial users to prepare their detail
specifications used in bilateral procurement contracts. A blank detail specification facilitates the comparison and
benchmarking of different materials. Furthermore, a standardized format makes procurement more efficient and more
error robust.
3.1.1.2
graphene
graphene layer
single-layer graphene
monolayer graphene
1LG
single layer of carbon atoms with each atom bound to three neighbours in a honeycomb
structure
Note 1 to entry It is an important building block of many carbon nano-objects.
Note 2 to entry As graphene is a single layer, it is also sometimes called monolayer graphene or single-layer
graphene and abbreviated as 1LG to distinguish it from bilayer graphene (2LG) and few-layered graphene (FLG).
Note 3 to entry Graphene has edges and can have defects and grain boundaries where the bonding is disrupted.
[SOURCE: ISO/TS 80004-13:2017 [23], 3.1.2.1]
3.1.1.3
graphene oxide
GO
chemically modified graphene prepared by oxidation and exfoliation of graphite
[SOURCE: ISO/TS 80004-13:2017, 3.1.2.13, modified – ", causing extensive oxidative
modification of the basal plane" has been deleted from the end of the definition.]
3.1.1.4
reduced graphene oxide
rGO
reduced oxygen content form of graphene oxide
[SOURCE: ISO/TS 80004-13:2017, 3.1.2.14]
3.1.1.5
graphene nanoplate
nanoplate consisting of graphene layers
[SOURCE: ISO/TS 80004-13:2017, 3.1.2.11]

3.1.2 Key control characteristics measured according to this document
3.1.2.1
key control characteristic
KCC
key performance indicator
material property or intermediate product characteristic which can affect safety or compliance
with regulations, fit, function, performance, quality, reliability or subsequent processing of the
final product
Note 1 to entry The measurement of a key control characteristic is described in a standardized measurement
procedure with known accuracy and precision.
Note 2 to entry It is possible to define more than one measurement method for a key control characteristic if the
correlation of the results is well-defined and known.
Note 3 to entry In ISO TC 16949 (now IATF 16949) , the term "special characteristic" is used for a KCC. The term
key control characteristic is preferred since it signals directly the relevance of the parameter for the quality of the
final product.
3.1.2.2
functional group
atom, or a group of atoms that has similar chemical properties whenever it occurs in different
compounds, which defines the characteristic physical and chemical properties of families of
organic compounds
[SOURCE: IUPAC]
3.1.2.3
oxygen functional group
functional group containing oxygen atom
3.1.3 Terms related to the measurement method
3.1.3.1
Boehm titration method
method to identify and quantify the functional groups through neutralization between oxygen
functional groups of different acidity and bases of different strength
Note 1 to entry Oxygen functional groups usually influence or determine the chemical and physical properties of
organic compound.
Note 2 to entry: See [14] and [15].
3.2 Symbols and abbreviated terms
HDPE high-density polyethylene
ΔE differential of potential to titrant volume
RSD relative standard deviation
4 General
4.1 Measurement principle
Oxygen functional groups on graphene of different acidities can be neutralized by bases of
different strengths (Figure 1). Sodium ethoxide (C H ONa) is the strongest base used here that
2 5
can neutralize acids including carboxyl groups (also in the form of their cyclic anhydrides),
lactone groups, hydroxyl groups and reactive carbonyl groups. Sodium hydroxide (NaOH) is the
second strongest base that can neutralize carboxyl groups (also in the form of their cyclic
anhydrides), lactone groups and hydroxyl groups. Sodium carbonate (Na CO ) neutralizes
2 3
lactone groups and carboxyl groups (also in the form of their cyclic anhydrides). And sodium

– 10 – IEC TS 62607-6-13:2020  IEC 2020
bicarbonate (NaHCO ) is the weakest base used here that neutralizes carboxyl groups (also in
the form of their cyclic anhydrides) only. Therefore, the content of each type of oxygen
functional group (mmol/g) can be determined from the difference between the normalized base
consumptions η (mmol/g), which are derived by dividing total base consumption (mmol) by mass
of reacting sample (g). For example, the difference between NaOH normalized consumption
(η ) and Na CO normalized consumption (η ) corresponds to the weakly acidic
NaOH 2 3 Na2CO3
hydroxyl group content. These four kinds of functional group (Table 1) can be differentiated by
neutralization with 0,05 mol/L solutions of NaHCO , Na CO , NaOH and 0,1 mol/L sodium
3 2 3
ethoxide, respectively.
Figure 1 – Test principle of Boehm titration
Table 1 – Four types of oxygen functional group and their structures
Terms Structure
O
Carboxyl
C
R OH
Lactone
Hydroxyl
Ph OH
Carbonyl
4.2 Sample preparation method
All the test specimens need to be dried prior to testing to remove residual moisture. Keep
graphene sample in a vacuum oven at (80 ± 5) °C until it is completely dry. Then cool it to room
temperature and store in a desiccator for use.

4.3 Description of measurement equipment / apparatus
4.3.1 Analytical balance, readability is 0,1 mg.
4.3.2 Electric thermostatic drying oven
4.3.3 Numerical control magnetic agitator/oscillator
4.3.4 Automatic potentiometer, with pH electrode and accurate to 0,1 mV.
4.3.5 HDPE bottles, the volume are 1 000 mL and 100 mL, with stopper.
4.4 Supporting materials
All reagents are listed in Table 2.[24][25][26]
Table 2 – Reagents used in this document
Item no. Reagent name Chemical formula Purity, Relative molecular Source
mass mass
fraction
% g/mol
O
H
1 Water Grade 2 18,02 ISO 3696:1987
C H OH
2 Ethanol 99,80 46,07 ISO 6353-2:1983
2 5
Sodium
3 NaOH 98,00 40,00 ISO 6353-2:1983
hydroxide
Sodium
Na CO
4 99,80 105,99 ISO 6353-2:1983
2 3
carbonate
Sodium
NaHCO
5 99,50 84,01 ISO 6353-3:1987
bicarbonate
C H ONa
6 Sodium ethoxide 99,50 68,05 ISO 6353-2:1983
2 5
7 Hydrochloric acid HCl 35,00 36,46 ISO 6353-2:1983

CAUTION: Take the necessary safety precautions when handling these materials.
4.5 Ambient conditions during measurement
The measurements can be performed under regular laboratory conditions without precise
temperature and humidity control.
5 Measurement procedure
5.1 Detailed protocol of the measurement procedure
5.1.1 Preparation of solutions
5.1.1.1 General
In the following, the amounts of reactants needed in order to obtain 1 L of test solution are
listed. All reactants should be dissolved using safe procedures. For complete dissolution of the
chemical compounds during solution preparations, the solutions should first be prepared with
500 mL of water contained in a 1 L volumetric flask unless specified otherwise. Then, gentle
shaking should be applied until complete dissolution is achieved. Finally, water should be added
to obtain a total volume of 1 L. Solutions are stored in a 1 L high-density polyethylene bottle.
Solutions shall always be used within 4 h after preparation to ensure they are fresh.

– 12 – IEC TS 62607-6-13:2020  IEC 2020
5.1.1.2 NaHCO solution: 0,05 mol/L (solution A)
4,20 g of NaHCO will yield 1 L of 0,05 mol/L solution.
5.1.1.3 Na CO solution: 0,05 mol/L (solution B)
2 3
5,35 g of Na CO will yield 1 L of 0,05 mol/L solution.
2 3
5.1.1.4 NaOH solution: 0,05 mol/L (solution C)
Dissolve 150 g of NaOH with 100 mL water in a beaker, shake well and store it in a PTFE bottle
until its supernatant becomes clear. Then 2,70 mL of the supernatant will yield 1 L of 0,05 mol/L
solution.
5.1.1.5 C H ONa solution: 0,1 mol/L (solution D)
2 5
Dissolve 6,805 g of C H ONa in high-purity, anhydrous, absolute ethanol, and dilute to mark in
2 5
a 1 000 mL volumetric flask and mix. Alternatively, purchase a certified solution and dilute it to
0,1 mol/L.
5.1.1.6 Titrant acid: 0,05 mol/L
Preparation: Fill a 1 L volumetric flask with about 500 mL of water. Then slowly dissolve 4,17 mL
of 12 mol/L HCl stock solution in the water. Finally, add more water until a total volume of
1 000 mL of HCl solution is obtained. The resulting solution is then poured into the titration
bottle of the automatic potentiometer.
Calibration: The calibration of the HCl solution is carried out using the dried working reagent
Na CO which has previously been air dried in electric thermostatic drying oven at (270–300) °C
2 3
as the primary standard. Dissolve 0,05 g (maximum permissible error of 0,000 1 g) of Na CO
2 3
in 30 mL of water in a titration cell of the automatic potentiometer. The obtained Na CO
2 3
solution with exact amount is then titrated with the above-mentioned HCl solution using an
automatic potentiometer. The titration's equivalence point occurs when ΔE is a maximum or
where the second differential Δ′E is zero. At least one blank titration is required. The volume of
titrant needed to reach the titration's second equivalence point is recorded as V and V .
1 0
Therefore, the concentration of the prepared HCl solution is
2××m 1000
C=
()V −VM
where
C is the concentration of the HCl solution, in mol/L;
m is the mass of Na CO , in grams;
2 3
V is the volume of HCl titration consumed for Na CO solution, in millilitres;
1 2 3
V is the volume of HCl titration consumed for blank titration, in millilitres;
M is the molar mass of Na CO , in g/mol, [M (Na CO ) = 105,99]
2 3 2 3
Perform at least three individual titrations for the calibration of the HCl solution, and then
calculate the arithmetical average value, precise to 0,000 01 mol/L. The above calibrated HCl
solution is titrant acid.
Cconcentrations of titrant acid can be decreased to 0,025 mol/L if the content of oxygen
functional groups of graphene is lower than 0,072 mmol/g, which is the lower limit for carbonyl.
2,30 mL of HCl will yield 1 L of 0,025 mol/L titrant acid.

5.1.2 Reactions between graphene and bases
a) Weigh four aliquot masses of 0,15 g to 0,5 g of dried sample into A1, B1, C1 and D1 HDPE
bottles, respectively; record the mass of graphene sample to the nearest 0,000 1 g as m ,
m , m and m . Then add 50,0 g of solution A into A1 HDPE bottle, add 50,0 g of solution B
2 3 4
into B1 HDPE bottle, add 50,0 g of solution C into C1 HDPE bottle, and add 40,0 g of solution
D into D1 HDPE bottle; record the exact mass of solutions A, B, C, and D to the nearest
0,000 1 g as m , m , m and m , respectively. For each bottle, seal with cap immediately
A B C D
after adding the solution and shake to mix the sample with the solution well. Then A1, B1,
C1 and D1 mixtures are obtained.
NOTE 1: After mixing NaOH with sample, N bubbling can be used for at least 20 minutes to remove CO .
2 2
However, both scientific reports [20][27] and experiment results have proved that the effect of CO on results is
very limited and can be negligible (see Annex B for details). So, it can be easily determined without going through
a pre-degassing process to remove the effect of atmospheric carbon dioxide (CO ).
b) Solution blanks (no sample) of each base are also conducted, i.e. add 50,0 g of solution A
into A0 HDPE bottle, add 50,0 g of solution into B0 HDPE bottle, add 50,0 g of solution C
into C0 HDPE bottle, and add 40,0 g of solution D into D0 HDPE bottle. The A0–B0 blanks
are obtained after sealing with a cap.
c) Sample blanks (no base solution) are meanwhile conducted in E HDPE bottles, i.e. mix
0,15 g to 0,5 g of graphene sample with 50,0 g of water and seal well with cap, record the
precise mass of sample and water to the nearest 0,000 1 g as m and m , respectively.
5 E
E sample blank is obtained after mixing well.
d) All nine sealed HDPE bottles are shaken for at least 3 h at (25 ± 2) °C using an oscillator.
e) Quickly filtrate all water solution bottles (A0, A1, B0, B1, C0, C1, E). For each bottle, perform
suction-filtration by means of a funnel with flat perforated plate using a filter paper to
separate the sample and the solution. For each bottle, abandon the first 15 mL of filtrate,
then without changing the filter paper or funnel, collect the remaining filtrate in another dry
filter bottle. The collected filtrate shall be titrated immediately after collection.
f) Centrifuge all ethanol solution bottles (D0, D1) to remove the graphene sample. For each
bottle, quickly transfer the solution into a 50 mL centrifuge tube and separate the sample by
means of a centrifugal separator at 10 000 r/min for 10 min. The supernatant shall be titrated
immediately after centrifugation.
NOTE 2 Before weighing sample into the HDPE bottle, both HDPE bottle and sample could be pretreated by an
electrostatic eliminator to avoid the loss during sample transfer.
NOTE 3 The concentration of the first 15 mL filtrate is lower than that of bulk filtrate owing to absorption of the filter
paper.
CAUTION: Take the necessary safety precautions when handling these materials.
5.1.3 Instrument preparation
Flush pipes of the automatic potentiometer at least three times before the titration experiment. Ensure
that gas bubbles in the automatic potentiometer pipes are expelled completely.
5.1.4 Titration of the filtrate
a) Weigh 10,0 g of the above collected A0 filtrate, A1 filtrate, B0 filtrate, B1 filtrate, C1 filtrate,
C0 filtrate, D0 supernatant solution, D1 supernatant solution into eight corresponding
titration cells of the automatic potentiometer and add 15,0 mL of water. The accurate mass
of supernatant solution or filtrate to the nearest 0,000 1 g are recorded as m , m , m ,
A0,t A1,t B0,t
m , m , m , m , and m , respectively.
B1,t C0,t C1,t D0,t D1,t
b) Weigh 20,0 g of the above collected E filtrate with 10,0 g of the above collected C0 filtrate
into a titration cell of the automatic potentiometer. The accurate mass of E filtrate and C0
filtrate in titration to the nearest 0,000 1 g are recorded as m and m , respectively.
E,t EC,t
– 14 – IEC TS 62607-6-13:2020  IEC 2020
c) These solutions are titrated with titrant acid conducted using an automatic potentiometer,
until the second titration’s equivalence point occurs when ΔE is maximum. Record the
volume V (HCl) of titrant acid corresponding to the second end-point as V V , V V
A0, A1 B0, B1
, V V , V V , and V , respectively.
C0, C1 D0, D1 E1
5.2 Measurement uncertainty
The uncertainties associated with measuring the surface oxygen functional groups of graphene
should be estimated from various origins as listed below:
a) uncertainties associated with weighing the mass of the powder, the working Na CO , the
2 3
solution A, B, C and D in reaction and filtrates in titration, which include the balance
calibration, weighing operation, and loss during sample transfer;
b) uncertainties associated with titration of the HCl solution and filtrates, which include the
uncertainty of automatic potentiometer, determination of the endpoint of titration curve.
5.3 Operation procedure, key control steps and case study
See Annex A for the operation procedure and key control steps, and Annex E for case study.
6 Data analysis / interpretation of results
6.1 Normalized base consumption
The number of bases (in mol) consumed for the neutralization reaction on the surface oxygen
functional groups of graphene sample, and normalized molar alkalinity of sample suspension
η , in mmol/g, are determined as follows:
E
η=(V×−Cm/ V ×Cm/)×m /m
A A0 A0,t A1 A1,t A1 1
η=(V×−Cm/ V ×Cm/)×m /m
B B0 B0,t B1 B1,t B1 2
η (V×Cm/ −×V Cm/)×m /m
C C0 C0,t C1 C1,t C1 3
η=(V×−Cm/ V ×Cm/)×m /m
D D0 D0,t D1 D1,t D1 4
η=((V×C−V×Cm/ ×m )/m )×m /m
E E C0 C0,t EC,t E,t E 5
where
η , η , η , η is the mole of NaHCO (A), Na CO (B), NaOH (C) and C H ONa (D)
A B C D 3 2 3 2 5
consumed for reaction between graphene sample and bases A, B, C
and D, respectively, in mmol/g;
η is the alkalinity of graphene sample suspension, in mmol/g;
E
m , m , m , m , m is the mass of the solution A, B, C and D and water in A1, B1, C1 and
A B C D E
D1 mixtures and in E sample blank, respectively, in grams;
C is the concentration of titrant acid, in mol/L;
m , m , m m m is the mass of the dried graphene specimens in A, B, C and D reaction
1 2 3, 4, 5
mixtures and F sample blank, respectively, in grams;
m , m is the mass of A0 filtrate and A1 filtrate in titration, respectively, in
A0,t A1,t
grams;
V , V is the volume of the titrant acid consumed by titration of A1 filtrate and
A0 A1
A0 filtrate, respectively, in millilitres;
m , m is the mass of B0 filtrate and B1 filtrate in titration, respectively;
B0,t B1,t
V , V is the volume of the titrant acid consumed by titration of B1 filtrate and
B0 B1
B0 filtrate, respectively, in millilitres;
=
m , m is the mass of C0 filtrate and C1 filtrate in titration, respectively;
C0,t C1,t
V V is the volume of the titrant acid consumed by titration of C1 filtrate and
C0, C1
C0 filtrate, respectively, in millilitres;
m , m is the mass of D0 filtrate and D1 filtrate in titration, respectively;
D0,t D1,t
V , V is the volume of the titrant acid consumed by titration of D1 filtrate and
D0 D1
D0 filtrate, respectively, in millilitres;
V is the volume of the titrant acid consumed by titration of E filtrate, in
E
millilitres;
m , m is the mass of C0 filtrate and E filtrate in titration of E filtrate,
EC,t E,t
respectively
Perform two individual measurements for the same sample. If the relative error of base
consumption in two parallel determinations does not exceed 10 % of the mean value, take the
arithmetical average value as the results, precise to 0,001 mmol/g, and report the relative error.
If the relative error in two parallel determinations exceeds 10 %, a repetition test is needed. It
is recommended to increase the sample amount to be reacted with the base solution in the
repetition test.
6.2 Oxygen functional group content
Content of oxygen functional groups on graphen
...