The artificial leaf. Credit: American Chemical Society |
A
detailed description of development of the first practical artificial
leaf—a milestone in the drive for sustainable energy that mimics the
process, photosynthesis, that green plants use to convert water and
sunlight into energy—appears in the ACS journal Accounts of Chemical Research.
The article notes that unlike earlier devices, which used costly
ingredients, the new device is made from inexpensive materials and
employs low-cost engineering and manufacturing processes.
Daniel
G. Nocera points out that the artificial leaf responds to the vision of
a famous Italian chemist who, in 1912, predicted that scientists one
day would uncover the “guarded secret of plants.” The most important of
those, Nocera says, is the process that splits water into hydrogen and
oxygen. The artificial leaf has a sunlight collector sandwiched between
two films that generate oxygen and hydrogen gas. When dropped into a jar
of water in the sunlight, it bubbles away, releasing hydrogen that can
be used in fuel cells to make electricity. These self-contained units
are attractive for making fuel for electricity in remote places and the
developing world, but designs demonstrated thus far rely on metals like
platinum and manufacturing processes that make them cost-prohibitive.
To
make these devices more widely available, Nocera replaced the platinum
catalyst that produces hydrogen gas with a less-expensive
nickel-molybdenum-zinc compound. On the other side of the leaf, a cobalt
film generates oxygen gas. Nocera notes that all of these materials are
abundant on Earth, unlike the rare and expensive platinum, noble metal
oxides and semiconducting materials others have used.
“Considering
that it is the 6 billion nonlegacy users that are driving the enormous
increase in energy demand by midcentury, a research target of delivering
solar energy to the poor with discoveries such as the artificial leaf
provides global society its most direct path to a sustainable energy
future,” he says.
Source: American Chemical Society
