Tiny metal nanoparticles are used as catalysts in many
reactions, from refining chemicals to producing polymers and biofuels. How well
these nanoparticles perform as catalysts for these reactions depend on which of
their crystal faces are exposed.
But previous attempts to design these nanoparticles by
changing their shape have failed because the structures are unstable and will
revert back to their equilibrium shape.
Now, researchers at Northwestern Univ.’s
Institute for Catalysis in Energy Processing have discovered a new strategy for
fabricating metal nanoparticles in catalysts that promises to enhance the
selectivity and yield for a wide range of structure-sensitive catalytic
reactions. The team, led by Laurence D. Marks, professor of materials science
and engineering at the McCormick School of Engineering and Applied Science,
discovered that they could design nanoparticles by designing the particle’s
support structure.
“Instead of trying to engineer the nanoparticles, we’ve
engineered the substrate that the nanoparticle sits on,” Marks said. “That
changes what faces are exposed.” Their results were published in Nano Letters.
This solution was a bit of a discovery: the team created the
nanoparticle samples, discovered that they didn’t change their shape (as the
laws of thermodynamics caused previously designed nanoparticles to do), then
set out figuring how it worked. It turns out that epitaxy—the relationship
between the position of the atoms in the nanoparticle and the position of the
atoms on the substrate—was more important to design than previously thought.
The team is currently testing the nanoparticles in a
catalytic reactor, and early results look promising, Marks says. The
nanoparticles appear to be stable enough to survive the rigors of long-term use
as catalysts.
“It opens the door to designing better catalysts,” Marks
said. “This method could be used with a variety of different metal
nanoparticles. It’s a new strategy, and it could have a very big impact.”
The Nano Letters
paper is titled “Oriented Catalytic Platinum Nanoparticles on High Surface
Area Strontium Titanate Nanocuboids.” The authors of the paper are James
A. Enterkin (first author), Kenneth R. Poeppelmeier, and Laurence D. Marks from
Northwestern.
The Northwestern Univ. Institute for Catalysis in Energy
Processing, funded through the US Department of Energy, Office of Basic Energy
Science, supported the research.
