Producing green hydrogen through the exposure of nanomaterials to
sunlight

Date:
January 21, 2021
Source:
Institut national de la recherche scientifique - INRS
Summary:
Researchers are paving the way towards the production of green
hydrogen.



FULL STORY ==========================================================================
A research team from the Institut national de la recherche scientifique
(INRS) has joined forces with French researchers from the Institute of Chemistry and Processes for Energy, Environment and Health (ICPEES),
a CNRS-University of Strasbourg joint research lab, to pave the way
towards the production of green hydrogen. This international team has
developed new sunlight-photosensitive- nanostructured electrodes. The
results of their research were published in the November 2020 issue of
the journal of Solar Energy Materials and Solar Cells.


==========================================================================
An Energy Transition Vector Hydrogen is being considered by several
countries of the Organisation for Economic Co-operation and Development
(OECD) as a key player in the transition towards decarbonized industries
and sectors. According to the INRS Professor My Ali El Khakani,
Quebec could strategically position itself in this energy sector of
the future. "Thanks to high-performance nanomaterials, we can improve
the efficiency of water dissociation to produce hydrogen. This "clean"
fuel is becoming increasingly important for the decarbonisation of
the heavy-duty trucking and public transportation. For example, buses
using hydrogen as a fuel are already in operation in several European
countries and in China. These buses emit water instead of greenhouse
gases," added the physicist and nanomaterials specialist.

Splitting water molecules into oxygen and hydrogen has long been done by electrolysis. However, industrial electrolyzers are very energy-intensive
and require large investments. The INRS and ICPEES researchers were
rather inspired by a natural mechanism: photosynthesis. Indeed, they
have developed specially engineered and structured electrodes that
split water molecules under the sun's light. This is a process known
as photocatalysis.

Challenges in the Design and Fabrication of the Nanostructured Electrodes
For maximum use of solar energy, the research teams have selected a very abundant and chemically stable material: titanium dioxide (TiO2). TiO2
is a semiconductor known for being photosensitive to UV-light, which
accounts only for 5% of the solar irradiance. Researchers have used
their expertise in the field to first change the atomic composition of
TiO2 and extend its photosensitivity to visible light. They were able
to produce electrodes that can absorb up to 50% of the light emitted
by the sun. A significant gain right from the start! The researchers
have then proceeded with the nanostructuration of the electrode to form
a network of TiO2 nanotubes that resembles a beehive-like structure.

This method multiplied the effective surface area of the electrode by a
factor of 100,000 or more. "Nanostructuring maximizes the ratio between
surface and volume of a material. For example, TiO2 nanostructures can
offer a surface area of up to 50 m2 per gram. That's the surface area
of a mid-size flat!," Professor El Khakani enthusiastically pointed out.

The final step of the electrode elaboration is their
"nanodecoration." This process consists of depositing catalyst
nanoparticles on the otherwise infinite network of TiO2 nanotubes to
increase their efficiency of hydrogen production.

To achieve this nanodecoration step, the researchers used the laser
ablation deposition technique, a field where Professor El Khakani has
developed a unique expertise over the last 25 years. The challenge
was not only to control the size, dispersion and anchorage of catalyst nanoparticles on the TiO2 nanotube matrix, but also to find alternatives
to the costly iridium and platinum classical catalysts.

This research identified cobalt oxide (CoO), a material that is quite
available in Quebec's underground, as effective co-catalysts for
splitting water molecules. A comparison of the two materials showed
that CoO nanoparticles enabled a tenfold increase the photocatalytic
efficiency of these new nanodecorated electrodes under visible light
compared to bare nanotubes.


========================================================================== Story Source: Materials provided by Institut_national_de_la_recherche_scientifique_-_INRS.

Original written by Audrey-Maude Ve'zina. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Thomas Favet, Thomas Cottineau, Vale'rie Keller, My Ali El Khakani.

Comparative study of the photocatalytic effects of pulsed laser
deposited CoO and NiO nanoparticles onto TiO2 nanotubes for the
photoelectrochemical water splitting. Solar Energy Materials and
Solar Cells, 2020; 217: 110703 DOI: 10.1016/j.solmat.2020.110703 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/01/210121131752.htm

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