Eons ago, nature
solved the problem of converting solar energy to fuels by inventing the process
sunlight to chemical energy in the form of biomass, while releasing oxygen as
an environmentally benign byproduct. Devising a similar process by which solar
energy could be captured and stored for use in vehicles or at night is a major
focus of modern solar energy research.
“It is widely
recognized that solar energy is the most abundant source of energy on the
planet,” explains University of Wisconsin-Madison chemistry professor Shannon
Stahl. “Although solar panels can convert sunlight to
electricity, the sun isn’t always shining.”
Thus, finding an
efficient way to store solar energy is a major goal for science and society.
Efforts today are focused on electrolysis reactions that use sunlight to
convert water, carbon dioxide, or other abundant feedstocks into chemicals that
can be stored for use any time.
A key stumbling
block, however, is finding inexpensive and readily available electrocatalysts
that facilitate these solar-driven reactions. Now, that quest for catalysts may
become much easier thanks to research led by Stahl and UW-Madison staff
scientist James Gerken and their
Writing in Angewandte Chemie, the Wisconsin group
describes a new high-throughput method to identify electrocatalysts for water
electrocatalysts that facilitate the oxidation of water are critical to the
production of solar fuels, says Gerken. “If we do this well enough, we can
keep the party going all night long.”
technology to store solar energy is not economically viable because using the
sun to split water into oxygen and hydrogen is inefficient. Water oxidation
provides electrons and protons needed for hydrogen production, and better
catalysts minimize the energy lost when converting energy from sunlight to
chemical fuels, says Stahl.
In addition to
being efficient, the catalysts need to be made from materials that are more
abundant and far less expensive than metals like platinum and the rare earth
compounds currently found in the most effective catalysts.
Stahl and Gerken, the discovery of promising electrocatalytic materials is
hindered by the costly and laborious approaches used to discover them. What’s
more, the sheer number of possible catalyst compositions far exceeds the number
that can be tested using traditional methods.
In the Angewandte Chemie report, Gerken, Stahl,
and their colleagues describe a screening method capable of rapidly evaluating
potential new electrocatalysts. In simple terms, the technique works using
ultraviolet light and a fluorescent paint to test prospective metal-oxide
electrocatalysts. A camera captures images from a grid of candidate catalysts
during the electrolysis process, as the paint responds to the formation of
oxygen. This approach turns out to be a highly efficient way to sort through
many compounds in parallel to identify promising leads.
Already, the Wisconsin team has identified several new metal-oxide
catalysts that are composed of inexpensive materials such as iron, nickel and
aluminum, and that hold promise for use in solar energy storage.