原子层沉积技术可能为未来能源提供新的解决方法,Atomic layer deposition fuels
future solutions to nation's energy challenges
The three images illustrate how a combination of anodized aluminum oxide (
AAO) and atomic layer deposition (ALD) provides precisely controlled, ultra-
uniform porous support for new and well-defined catalysts. Credit: ANL
[纳米科技世界快讯]More efficient and less costly solar cells, solid-state
lighting and industrial catalysts are potential applications of atomic layer
deposition (ALD), a technique that researchers at Argonne National
Laboratory are working to perfect. Other potential applications are improved
superconductors and separation membranes.
ALD is a thin-film growth technique that offers the unique capability to
coat complex, three-dimensional objects with precisely fitted layers. The
scientists expose an object to a sequence of reactive gas pulses to apply a
film coating over the object's surface. The chemical reactions between the
gases and the surface naturally terminate after the completion of a "
monolayer" exactly one molecule thick. ALD can deposit a variety of
materials, including oxides, nitrides, sulfides and metals.
What makes ALD more effective and flexible than traditional methods for
producing thin film coatings, such as evaporation, is its ability to coat
every nook and cranny of a complex object.
Scientists use this procedure to fabricate nanostructured catalytic
membranes, or NCMs. These structures enable catalytic reactions that, for
example, convert inexpensive feedstocks into valuable products and
synthesize hydrocarbon fuels. Argonne has filed for a patent on NCMs.
“We are focusing our attention now on measuring the properties of the
catalysts and synthesizing other catalytically relevant materials inside the
NCMs,” said Jeffrey Elam, a research chemist in Argonne's Energy Systems
Division.
Elam, along with Michael Pellin of Argonne's Materials Science Division, has
been working with NCMs to carry out chemical reactions to produce materials
that help the nation sustain itself in a more cost-effective and efficient
manner.
One of the Argonne researchers' goals has been to improve the effectiveness
of the catalyst in Fischer-Tropsch synthesis. The Fischer-Tropsch process
takes syngas, a mixture of carbon monoxide and hydrogen, and converts it
into hydrocarbon fuels. Syngas can come from a variety of materials,
including natural gas, coal or biomass.
Elam and Pellin hope that Argonne's NCMs can improve the performance of
Fischer-Tropsch catalysts enough to make the production of clean, sulfur-
free fuels economically viable in the next decade or two.
Recently, Argonne researchers also have begun to apply ALD technology to
solid-state lighting, which uses light-emitting diodes, or LEDs. Unlike
incandescent light bulbs, LEDs consume little electric power and do not burn
out or overheat. They are illuminated by the movement of electrons in a
semiconductor and are considered the most efficient light source in
existence. LEDs can be found in many electronic devices, from digital
displays to traffic lights.
LEDs require a conducting electrode to supply electricity to the
semiconducting material, but this electrode must also be transparent to
allow the light to escape. Traditionally, this transparent conducting
electrode is made from indium-tin oxide (ITO); however, ITO is too expensive
for mass production.
To replace ITO, Argonne researchers are exploring chains of metal
nanoparticles aligned in a magnetic field to form an electrically conductive
web. ALD coatings are applied to these networks to form a transparent,
conducting electrode to make cheaper LEDs. This research is funded by the U.
S. Department of Energy to develop advanced solid-state lighting
technologies that, compared to conventional lighting technologies, are much
more energy efficient, longer lasting and cost-competitive by 2025.
In cooperation with Northwestern University, Argonne researchers are also
fabricating highly efficient solar cells for converting sunlight into
electricity. These improved, dye-sensitized solar cells (DSSCs) use ALD
technology in a similar way to NCMs – precisely fitted layers of
transparent, conducting oxides and semiconductors are deposited on the inner
surfaces of nanoporous membranes.
The researchers aim to eventually commercialize these novel and efficient
solar cells. Because no pure, costly silicon is involved in the fabrication
process—as it generally is with conventional solar cells—the researchers
hope to produce electricity at a much lower cost.
Source: Argonne National Laboratory
