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Led by professor Daniel Nocera, researchers at MIT have been
working on technology which mimics the photosynthetic process in leaves to
directly convert sunlight into chemical fuel. The breakthrough came about when
the team came across an inexpensive combination of materials to catalyze the
electrolysis of water. The design is meant to allow for simple and convenient
solar energy capture.
The artificial leaf, shown with some
real leaves, both which convert energy from sunlight into chemical form. Photo:
Dominick Reuter
The 'artificial
leaf', as it is called, is a silicon solar cell with catalytic materials
layering both sides. When immersed in water, this device produces oxygen and
hydrogen gas as it is exposed to sunlight. These gases can then be sent to a
fuel cell to produce electricity. The device requires no external controls or
wiring to use, and is made of inexpensive materials (mostly silicon, cobalt,
and nickel). A video showing its operation can be seen here.
A diagram of the design and function
of the artificial leaf. Photo: ScienceNow
This is not to be confused with separate artificial photosynthesis technology also sometimes referred to as an artificial leaf
(discussed in a previous
entry), which uses water and carbon dioxide to create a hydrogen/carbon
monoxide syngas. A team at the University of Illinois leads this project, and
has made progress in improving the poor efficiencies of the technology through
the use of ionic solvents to stabilize carbon dioxide solutions.
MIT's device is not fully functional in its current form.
The biggest obstacle is developing an effective and efficient way to collect
and store the gases. Proper separation and safe storage of these extremely
volatile gases much be achieved at a reasonable cost to keep the feasibility and
of this project within reach. The nominal conversion efficiencies of the cells
themselves are also lacking in comparison to commercial solar cells (2.5-4.7% as
compared to >10%). "It's a step," Nocera says. "It's heading in the right
direction."
The concept behind the artificial leaf is not a new one, but
this device's steps towards practicality are commendable. Catalyzed
electrolysis provides a means of capturing solar energy directly into fuel
form, reducing the problems associated with intermittent and inconsistent
generation. The device itself attempts to make the utilization of this process
more feasible by creating technology that is less expensive to manufacture and
less complex to operate or maintain than traditional solar cells.
Recently, a discovery was made at MIT regarding a new
catalyst (discussed in the previous
entry) for a similar process using an alkaline solution rather than pure
water. Future developments will likely focus on implementing this catalyst in
the artificial leaf to boost efficiency. In addition, the team will be working
to build the device using other materials, including iron oxide, which may be
even cheaper than silicon.
Sources:
MIT News
Wired
- ScienceNow
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