Chemical Engineering May 2022 - 9

Capillary-fed electrolysis unlocks new levels of
efficiency for green-hydrogen production
A
new category of electrolysis could significantly
lower the expenses associated
with producing " green " hydrogen.
In the new capillary-fed electrolyzer
cell - designed by Hysata (Wollongong, Australia;
www.hysata.com) based on research
from the University of Wollongong (www.uow.
edu.au) - water is supplied to electrodes
using capillary transport facilitated by a commercially
available wicking membrane.
" Rather than having the electrodes surrounded
by liquid as in a standard electrolyzer,
this wicking membrane takes liquid from a reservoir
below the electrodes and delivers targeted
electrolyte between the two electrodes. The porous
membrane has a very high open area and a
much lower electrical resistance than the separators
used in other electrolysis methods. This
gives us very high current density and low voltages,
resulting in a high electrical efficiency with
low costs, " explains Paul Barrett, CEO of Hysata.
This configuration also means that the electrodes
are continuously coated with a thin layer
of electrolyte through which the generated O2
and H2 gases can efficiently travel without
forming gas bubbles, which can hinder access
to active sites on the electrodes. Being able
to directly produce gases at the electrode interfaces
without bubbles or froth in the liquid
helps the capillary-fed electrolyzers to avoid
resistance and mass-transfer inefficiencies
experienced in other electrolyzers, and also
decreases the amount of water required. According
to Barrett, the new electrolyzers work
at 95% overall system efficiency, compared
to around 75% for current industry-standard
electrolysis units - translating to a H2 production
cost of $1.50/kg or less. " The high-efficiency
cells enable balance-of-plant simplification
in a number of ways, including eliminating
the need for cooling, and we can take the gas
off the stack at higher pressure, eliminating the
need for compression, " he adds.
Hysata has designed the cell architecture to
be mass-produced - the cell itself is injectionmoldable
from widely available polymeric materials,
and all other core components, including the
wicking membrane, are made of off-the-shelf
materials. Furthermore, unlike typical electrolyzers,
the electrodes require no precious metals.
The team is working on 5-MW cells modules,
with gigawatt-scale manufacturing targeted
to begin in 2025. These modules will form the
building blocks for larger deployments.
n
through the choice of
hydrocarbon starting
compounds.
Membranes made by
the researchers show
promise to drastically
improve the performance
of gas-separation
processes. For example,
separating CO2
from methane, these
new membranes have
five times the selectivity
and 100 times the
permeability of existing
cellulosic membranes
for that purpose. Similarly,
they are 100 times
more permeable and
three times as selective
for separating hydrogen
from methane.
An MIT spinoff company
called Osmoses, led by
authors of this study,
recently won the MIT
$100K entrepreneurship
competition and
has been partly funded
by The Engine (www.engine.xyz)
to commercialize
the technology. ❐
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Chemical Engineering May 2022

Table of Contents for the Digital Edition of Chemical Engineering May 2022
