che_february-2025 - 31

Feature Report
Part 2
Proton-Exchange Membranes:
Design Strategies for Water
Electrolysis
Designing a proton-exchange membrane that will balance the efficiency, durability
and safety requirements for hydrogen production requires careful consideration of
materials and chemistry
A
mong the ongoing efforts to curb
climate change, researchers are
actively pursuing the further development
of water electrolysis
technologies for the production of cleaner
hydrogen. " Green " hydrogen can be manufactured
through water electrolysis using
renewable energy. One method of water
electrolysis utilizes a proton-exchange
membrane (PEM). Compared to other
water electrolysis methods, PEM electrolysis
demonstrates several key advantages,
including compact design, high electrolytic
efficiency, stability and a robust response
to fluctuating power sources [1-3]. The
mechanics of a PEM electrolysis cell are
depicted in Figure 1. Within the electrolysis
cell, a PEM, usually less than 200 mm
in thickness, separates the anode and cathode.
Upon applying voltage, water electrolysis
proceeds in the following sequence:
1. Water is oxidized at the anode, generating
protons and oxygen
2. The protons are transported to the counter-electrode
(cathode) through a PEM
3. Protons are reduced at the cathode, and
hydrogen is produced
A gas-diffusion layer (GDL) helps to facilitate
the efficient release of generated gases
during water electrolysis, thus inhibiting
bubble adhesion on the catalyst layer. As a
result, water can access the catalyst more
efficiently at the anode, promoting the oxidation
reaction of water.
In industrial applications, hydrogen is utilized
as a high-pressure gas. Therefore, two
types of compression methods are typically
considered for water electrolysis. One
involves compressing ambient-pressure
hydrogen produced by water electrolysis
using a compressor. The other method involves
elevating the pressure (to greater than
3 MPa) of the produced hydrogen within a
sealed electrolytic cell and cylinder. In the
latter method, especially in
cases where only the cathode
side is pressurized (denoted
as differential highpressure
water electrolysis),
there is no need for a compressor,
which can lead
to more efficient hydrogen
production [4].
Hydrogen obtained from
FIGURE 1. A typical structure of a PEM cell for water electrolysis is depicted here [1 ]
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
water electrolysis contains
moisture that often must be
removed prior to the hydrogen's
end-use application.
However, pressurizing hydrogen
within water electrolyzers
decreases the water
content of the generated
hydrogen. Therefore, differential
high-pressure PEM
FEBRUARY 2025
31
Yusuke Chiba,
Shintaro
Hayabe and
Toshiaki
Sawada
AGC Inc.
Shunsuke
Tsukuemoto
and Will Salem
AGC Chemicals
Americas
IN BRIEF
MAKING AN EFFECTIVE
PEM
PFSA POLYMERS
PEM DESIGN STRATEGY
http://WWW.CHEMENGONLINE.COM
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