Sunday, February 11, 2007

Contender 3: Make "Artificial Leaves" to capture CO2

Green leaves consume CO2, so why can't we?
Artificial Photosynthesis

Contender 3: Make "Artificial Leaves" to capture CO2

Physics News Update: Number 597 #3,

July 9, 2002
by Phil Schewe, James Riordon, and Ben Stein

Artificial leaves, made from semiconductors, might one day
help to remove excess airborne carbon dioxide and
maybe even turn it into fuel.

Real leaves, the green ones deployed by plants,
perform many valuable tasks, not the least being
the removal of CO2 from air and its replacement
with breathable O2.

Artificial CO2 fixation needs several ingredients:
light, a catalyst (such as CdS), and organic molecules.

A new study by a Oak Ridge-Vanderbilt team of physicists
suggests how this process can be made more efficient,
a necessary step if artificial fixation is ever to be practical
on a large scale.

Contrary to previous ideas, the study shows, fixation does not
take place directly on the catalyst surface.
Rather it's a two step process:

1) ionization of the CO2 occurs at the surface,
creating a highly reactive radical which can

2) later combine with other CO2 molecules or
organic molecules in the vicinity.

Stephen Pennycook says that his study looks at
the role of catalyst surface roughness
(flat planes of CdSe don't work as photocatalysts,
but nanocrystals of the same material do)
and at the possibility that nanocrystal doping might
obviate the need for light, which would allow some fixation
to take place in dark smokestacks.

Oak Ridge National Laboratory (ORNL) research

ESF Task Force for Clean Solar Energy

The European Union and its member states are being urged
by leading scientists to make a major multi million Euro
commitment to solar driven production of
environmentally clean electricity,
hydrogen and other fuels, as the only sustainable
long-term solution for global energy needs.

The most promising routes to eventual full-scale
commercial solar energy conversion directly into fuels
were identified at a recent international meeting
in Regensburg, sponsored by the European Science Foundation (ESF).

Participants at the ESF’s brainstorming conference,
describe the solar fuels project as the quest for
building the "artificial leaf".

There is growing conviction in Europe and elsewhere that,
by 2050, a large proportion of our fuels will come from
such "artificial leaves", and that there is no time to lose
starting the crucial enabling research, in order to gain
technology leadership in this important future key technology.

European Science Foundation (ESF) research

Scientists at Australian CSIRO's Telecommunications and
Industrial Physics are developing artificial photosynthesis,
which copies what plants do by taking light and carbon dioxide
and converting them to energy to produce food.

"By imitating this process with a mix of manufactured materials
instead of chlorophyll, we are hoping to develop technology
that can reduce the large amounts of carbon dioxide emitted
into the atmosphere from power stations and cars."

"Byproducts of the process could be a valuable alternative fuel,
methane, or even food in the form of starches and sugars."

The research is still in its early days, but has started to
show encouraging results according to Dr Braach-Maksvytis.

CSIRO Australia research

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