University of Pittsburgh researchers have developed a composite nanomaterial that is stable at high temperatures.
Götz Veser, an associate professor of chemical and petroleum engineering in the University of Pittsburgh’s Swanson School of Engineering, and Anmin Cao created the 4nm-sized metal-alloy particles of platinum and rhodium that could withstand temperatures of more than 850oC, at least 250 degrees more than typical metallic nanoparticles.
Previous attempts to stabilise the metals have involved encasing them in heat-resistant nanostructures, but the most promising methods only produced particles in the 10nm to 15nm range.
To make their nanoparticles, the researchers created a blend of platinum and rhodium, which has a high melting point. They tested the alloy via a methane combustion reaction and found that the composite was not only a highly reactive catalyst, but that the particles maintained an average size of 4.3nm even during extended exposure at 850oC.
Small amounts of the 4nm particles remained after the temperature topped 950oC, although the majority had increased to eight times that size.
Veser and Cao discovered that the alloy sacrificed the low-tolerance platinum at high temperatures, then reconstituted itself as a rhodium-rich catalyst to finish the reaction. At around 700oC, the platinum-rhodium alloy began to melt. The platinum then ‘bled’ from the particle and formed larger particles with other errant platinum, leaving the more durable alloyed particles.
Veser and Cao predict that this self-stabilisation would occur for all metal catalysts alloyed with a second, more durable metal.
Veser and Cao conducted their work with support from the National Energy Technology Laboratory, the lead research and development office for the US Department of Energy’s (DOE) Office of Fossil Energy, as well as the DOE’s Office of Basic Energy Sciences and the National Science Foundation.