Sulfonic acid-crosslinked nanocellulose as a novel polymer
electrolyte membrane for hydrogen fuel cells
SELYANCHYN Olena

Graduate School of Integrated Frontier Sciences, Department of Automotive Sciences, Kyushu University
MACROSCOPIC & MICROSCOPIC MORPHOLOGYHYDROGEN FUEL CELL
O2

Fuel cell - core technologi`cal element of thesustainable “Hydrogen society”

electrolyte (PEM)
anodeCe3 x 3 cm

Barriers of wide deploymet:> Cost of hydrogen fuel> Lack of infrastructure (e.g. fuelling stations)> Cost of fuel cells (Pt in electrocatalyst, bipolar
plates and proton exchange membrane)

bipolar plategas diffusion layer
cathodeO2

Benchmark materials for PEM - perfluorinatedsulfonic acid ionomers: Nafion®, Aquivion®, 3M®

ll n-1H2F2CCell nProton exchange H2
membrane fuel cell
(PEMFC)

Ce

F2
C

6.6

F2C+1

3%SSA@CNC
9%SSA@CNF
bottom surface

Conventional paper

7%SSA@CNC

10%SSA@CNC
CNC surface

9%SSA@CNF
top surface

20%SSA@CNC
7%SSA@CNC surfacenFC

F2CO

F2CO

F2CSO3H

CF320 μm

Disadvantages: high-cost, degradation, non-recyclable

Purpose of this work:

CNC

Nafion®

FC

Proton conductivity ~ 100 mS/cm
IEC ~ 0.9 mmol [H+]/g
Cost ~ US$600 to 1200 per m2ll nnanocrystal-based

2 μm

CNF paper [hot-press]

1 μm

2 μm

1 μm

SSA@CNF [hot-press]

Development of low-cost and efficient PEM based on nanocellulose
RESEARCH MATERIAL: NANOCELLULOSE

Ordered (crystalline) domains

50°C

Z'' / Ω

-10k

-20k

20% RH

100% RH

60°C

0070°C
80°C
90°C

10k

20k

30k

40k

50k

060k

010k

Conventional
cellulose(microﬁbers)

30k40k

50k

0.1

1.73
1.03

0.13

0.04

0.05

CNF 3%-SSA 5%7%9%Strong dependence of σ on relative humidity, weaker dependence on temperature (9%-SSA@CNF).
Crosslinking of the CNF with SSA resulted in ca. 40 times increased proton conductivity compared
to unmodified CNF sample.

Disordered (amorphous) regions

strong acid treatment

20k

Conditions:
1 90 ºC, 95% RH

Z' / Ω

Z' / Ω

mechanical shearing(PRELIMINARY RESULTS ): COMPARISON WITH LITERATURE
Composites withlow content of cellulose

GlucoseOHHOOHOHOOOHOHOHOOH

OH

O

OO

HO

OH

OH

O

nOH

Proton conductivity (mS⋅cm-1)

Nanocellulose

OH

Cellobiose

OH
O
HOOH

hydrogen-bonds
∗O

OH

HOOH

HOO

OH

O

O

OH
O

HOOH

HOO

OH

O

HOO

OH

OH

HO∗O

O
OH

HOOO S O

OH

O

O

OH

Sulfosuccinic acidOH

sulfonic group

∗HO

OH

HO
O
O
O

hydroxyl group

∗O
HO

OH

SO

HO
O

O

O

HO

O

ertseO
O
H
O
OH

sondb

HO

OH

O

S

∗O

O

O

O

OH

O

OH

O
O

HO

O

O
O
OH

HO

OH

OO

∗MACROSCOPIC & MICROSCOPIC MORPHOLOGYCNF paper

Sriruangrungkamol, 2020 (TP)85

BC/Nafion

9%SSA@CNF

2090

Tri 20%1094

Tri 16%3080

MFC/Nafion

60

CNC with residual
sulfonic groups

90

AMPS-g-BC
BC/PMACC
CNC(78%)/Im30

Tri 13%

BG 80%PANI 6.4%

1

MFC@SSAMFC/RDPS-CNC/Tri/PVA

BC/Fucoidan/Tannic acid

Carboxylated
CNF
CNF withresidual
sulfonicgroups

CNF@SSA

BG 80%
CNC(75%)/Im

Tri 9%

1020

BG 60%

3040

Unmodified BC, CNF(hydrated)

50

6070

Cellulosic material content (%)

8090100

Vilela, 2020 (TP)Vilela, 2016 (TP)Gadim, 2014 (TP)Jiang, 2015 (IP)
Gadim, 2016 (IP)Vilela, 2017 (TP)Wang, 2019 (TP)Ni, 2018 (IP)Ni, 2018 (IP)Cai, 2018 (IP)Zhao, 2019 (IP)Zhao, 2019 (IP)Di, 2019 (IP)
Rogalsky, 2018 (TP)Tritt-Goc, 2019 (?)
Tritt-Goc, 2020 (?)
Etuk, 2020 (TP)- Results of this work compared to literature shows that utilization of asid crosslinked nocellulose
allows substantial increase in the proton conductivity and fabrication of thinner membranes.
- Considering high gas barrier of nanocellulose membranes PEMs with competitive properies(specific resistance, chemical & mechanical stability) can be fabricated, that are environmentallyfriendly and have substantially lower cost compared to benchmarks (e.g. Nafion).

OH

crosslinked cellulose

One-step approach

Conventional paper

HOO

O

25%SSA@CNC

Seo, 2009 (IP)Lin, 2013 (TP)Guccini, 2019 (TP)O.Selyanchyn, R.Selyanchyn & S.M.Lyth* Front.Energy.Res. 2020, doi.org/10.3389/fenrg.2020.596164

OHOH

BG 95%0OH

HO∗O

hot-press(oven)

OH+OH
OH

O

OH

BC/PMOEPBC/Nafion

0.1

130 ºC

Bayer, 2016 (TP)PSS/BC100

nanofibers

MODIFICATION APPROACH: SULFONIC ACID CROSSLINKING

Maximum concentration of SSA
in CNF ~ 10 wt%, up to 50 wt%
can be blended with CNC

-30k

-10k

Molecular structure

Membranes of 3-30 microns inthickness are distinctively different from conventional cellulosic
membranes (e.g. paper), freestanding and self supporting.

-40k

Z'' / Ω

Higher plants, bacteria,simple animals (e.g. tunicates)

mechanical,
chemical tretment“Eco-friendly, low-costmaterial for fuel cellapplications”

Hypothesis: surface of nanocellulose covered with sufficient amount of sulfonic acidgroup (strong proton conducting moiety) will make agood proton conductor.

40°C

-20k

Plant cell wall

∗

-50k

40% RHnanocrystals

Crosslinking: one-step reaction between mixed acid andnanocellulose results in aformation of multiple ester
bonds disrupting the naturalhydrogen-bonding networkof cellulose.

60% RH

80% RH

Proton conductivity (mS/cm)

Cellulose
Hemicellulose
LigninMembranes features- uniform thickness in casted
membranes (aqueous solution)- natural drying (no extra energy)- suitable for mass production- flat and stable after hot-pressing

2 μm

PROTON CONDUCTIVITY OF CROSSLINKED MEMBRANES-30k

Characteristic properties:- high mechanical strength- low density & high surface area
- non toxicity & biodegradability- flexibility

10 μmLower thickness of nanocellulose PEMs is possible due to material properties + high gas barrier- Thickness of the CNF and SSA@CNF membranes is below 10 µm- State-of-art Nafion in Toyota Mirai: 2008 (~50 µm); 2017 (14 µm); goal for 2020 - 10 µm

Nanocellulose can be obtained from various types of plants bymechanochemical processing or directly in bacteria:- strong acid treatment- mechanical shearing- grown in microorganisms
Main types of NC:- cellulose nanocrystals (CNC)- cellulose nanofibers (CNF)μ10 μmnanofiber-based
3%-SSA@CNF

CONCLUSIONS & FUTURE WORK
1. Nanocellulose is a promising biopolymer platform for the development of novel PEM
for fuel cell applications.
2. Structural integrity of the organic acid crosslinked cellulose nanofiber andnanocrystal membranes was proven in the region of sub-10 micron thicknesses.
3. Morphological features (SEM), chemical structure (FTIR) and swelling behaviour
in water suggest a promising material with competitive proton conductivity.
Future experiments: mechanical properties, proton conductivity at high temperatures,chemical stability in hot water, O2 and H2 permeability, fuel cell performance.

ACKHOWLEDGEMENT:5 x 5 cm
[hot-pressed]

Kyushu University Platform of Inter/Transdisciplinary
Energy Research Support Program for Doctoral Students

E-mail: olenaselyanchyn@gmail.com / Corresponding author: Prof. S.M. Lyth lyth@i2cner.kyushu-u.ac.jp / The Lyth Lab: https://sites.google.com/view/lythlab/