Tech Briefs Magazine - August 2022 - 47

Two of the photocatalyst materials tested
as part of the study performed better
than titanium dioxide did in its bare state,
the scientists said. The findings suggest
that further study of those materials could
yield promising photocatalysts.
" If you have a bare compound that behaves
much better than titanium dioxide
then we know this is a potential material
to optimize, " Wang said. " If we find the
right co-catalysts for those materials, we
can improve them by orders or magnitude
and these materials could eventually
be useful in water splitting. "
The team said the system is and easy to
build from commercially available components.
It features a low leakage rate
and a small reaction chamber volume
size, which allows three orders of magnitude
higher detection sensitivity for hydrogen
evolution than a conventional
gas chromatography system.
For more information, contact Patricia
Craig at plc103@psu.edu; 814-863-4663.
Advancing Renewable Energy Production with Solar
Thermochemical Hydrogen
An emerging water-splitting technology could be potentially more energy efficient than
producing hydrogen via the commonly used electrolysis method.
National Renewable Energy Laboratory, Golden, CO
P
erovskite materials may hold the potential
to play an important role in a
process to produce hydrogen in a renewable
manner, according to an analysis
from scientists at the National Renewable
Energy Laboratory (NREL).
Hydrogen has emerged as an important
carrier to store energy generated by
renewable resources, as a substitute for
fossil fuels used for transportation, in
the production of ammonia, and for other
industrial applications. Key to the successful
use of hydrogen as a fuel is being
able to meet the Department of Energy's
Hydrogen Energy Earthshot - a recently
announced goal to cut the cost of
clean hydrogen by 80 percent to $1 per
kilogram in a decade.
The NREL scientists analyzed an
emerging water-splitting technology
called solar thermochemical hydrogen
(STCH) production, which can be potentially
more energy efficient than producing
hydrogen via
the commonly
used electrolysis method. Electrolysis
needs electricity to split water into hydrogen
and oxygen. STCH relies on a
two-step chemical process in which metal
oxides are exposed to temperatures
greater than 1,400 °
C and then re-oxidized
with steam at lower temperatures
to produce hydrogen.
" It's certainly a very challenging field,
and it has a lot of research questions still
unanswered, mainly on the materials
perspective, " said Zhiwen Ma, a senior
engineer at NREL and lead author of a
new paper, " System and Technoeconomic
Analysis of Solar Thermochemical Hydrogen
Production, " which appears in
the journal Renewable Energy. His co-authors,
all from NREL, are Patrick Davenport
and Genevieve Saur.
Tech Briefs, August 2022
The paper complements ongoing materials
discovery research by looking at the
system-level design and techno-economic
analysis for integrating materials into a solar-fuel
platform and supporting the Department
of Energy's HydroGEN program.
The material discovery in the HydroGEN
program involved machine learning, defect
calculations, and experimental work to
develop new perovskite materials. The researchers
need to identify perovskites capable
of handling the high temperatures required
while hitting performance targets.
This work shows part of a portfolio of
techno-economic analysis focused on hydrogen
production pathways each with
its own advantages and disadvantages.
Electrolysis, for example, is commercially
available and the electricity required
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can come from photovoltaics (PV). The
PV cells used, however, only capture a
section of the solar spectrum. STCH uses
the entire spectrum. The concentrated
solar thermal power enables STCH to
create the chemical reaction.
Active research to identify the best materials
for the STCH process is critical to
the success of this method for hydrogen
production, the scientists noted.
" The material has not necessarily been
found, " Saur said, " but this analysis is to
provide some boundaries for where we
think the costs will be if the materials meet
some of the targets and expectations that
the research community envisions. "
For more information, contact David
Glickson at David.Glickson@nrel.gov; 303275-4097.
47
Planar-Cavity
Receiver
Reactor
Step 1:
High Temp
Reduction
Alternating Recievers
Cycles
O2
Step 2:
Low Temp
Oxidation
Condensor
Control
Room
Concentrated
Radiation
H2O
Receivers
Solar Field
Heliostats Pivot
to Alternate Cycles
H2
A conceptual solar thermochemical hydrogen production platform. (Image: Patrick Davenport, NREL)

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Tech Briefs Magazine - August 2022

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