October 21 2008 / by Garry Golden
Category: Energy Year: 2018 Rating: 2
Scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory have taken the first-ever glimpse of nanoscale catalysts in action.
Why should we care about catalysts?
The future of clean abundant energy depends on our ability to lower the costs of chemical reactions in energy conversions involving light, hydrogen, carbon, and oxygen. These are the foundations of most energy systems, and basis for developing ‘green chemistry’ that avoid harmful byproducts.
If we want to create low cost solar cells or improve batteries and hydrogen fuel cells, we must advance our knowledge and nano-engineering of catalysts. If we want to reduce the impact of harmful emissions from coal, oil and natural gas, we must turn to catalysts.
Nanoscale design of shapes
Catalysts speed up chemical reactions. At the most basic level shape matters. To improve performance we can design catalysts at the ‘nanoscale’ (billionth of the meter) to change properties of low cost abundant elements rather than rely on expensive precious metals. At the nanoscale we design higher surface area to increase chances of molecules reacting, and we can design shapes so that they have high selectivity to deal with a certain type of molecules (e.g. capturing sulfur, releasing hydrogen).
Up until now, scientists have only dealt with snapshot images of catalysts before or after. Never live, in action. Now Berkeley scientists have changed the game. “By watching catalysts change in real time, we can possibly design smart catalysts that optimally change as a reaction evolves,” Gabor Somorjai, a renowned surface science and catalysis expert.
Berkeley researchers are confident that catalysts can be designed to decrease the harmful effects of pollutants, improve performance of energy storage systems like batteries and hydrogen fuel cells and create ‘greener’ liquid fuels and feedstocks associated with ‘green chemistry’ in which waste byproducts are minimized.
What happened? Video explanation?
Using a state-of-the-art spectroscopy system at Berkeley Lab’s Advanced Light Source, the team watched, for the first time, as nanoparticles composed of two catalytic metals changed their composition in the presence of different reactants. Until now, scientists have had to rely on snapshots of catalysts taken before and after a reaction, never during.
“It’s difficult to tune a catalyst to do exactly what you want unless you know how it adapts during a reaction,” adds Miquel Salmeron, a pioneer in a field of spectroscopy that enabled this work “With our work, we can for the first time see what the catalyst is doing during the reaction, not before and after.”
The scientists watched, in real time, as the bimetallic nanoparticles restructured themselves when exposed to different gases, such as nitrogen oxide, carbon monoxide, and hydrogen. In the presence of some reactants, rhodium rose to a particle’s surface. While in the presence of other reactants, palladium rose to the surface.
“From one gas to another, we observed different metals segregating to a catalyst’s surface, which is the part of the catalyst that drives chemical reactions,” says Somorjai. “And this makes all the difference in establishing how the catalyst participates in the chemistry.”