Designing Inorganic Nanomaterials for Energy and Soft-Electronics Applications
Written by Elizabeth Wilson
Taeghwan Hyeon is a prolific materials scientist, with over 400 publications and 74,000 citations under his belt. At Thursday’s Symposium X, Hyeon, who is with Seoul University, took his audience on a tour of recent highlights in his over-30-year career, including advances in fuel cell materials, and soft electronics for heart failure, while always stressing the importance of collaboration with his many colleagues.
Proton-exchange membrane fuel cells are the future of energy for transportation, Hyeon said. But the catalysts required to produce hydrogen rely on rare, expensive platinum. “It’s impossible to get a good quality fuel cell electrode out of non-platinum materials,” he said. They key, then, is to use less of it, and increase its activity. Many groups are working on this issue. Hyeon’s group’s angle was to develop nanoparticles made of platinum iron alloys. However, the synthesis requires heating the nanoparticles, which causes the nanoparticles to coalesce into larger particles. Their solution was to coat the nanoparticles with polydopamine before heat treatment, which protects the particles, and they remain small. The result is a fuel cell that loses only 3% activity after 100 hours operation, a record high 10 times higher activity than some other similar catalysts.
Hyeon’s curiosity has also drawn him to materials with medical applications, in particular, heart failure. Heart disease is the leading cause of death in the U.S., and one third of those deaths are caused by heart failure. As a heart fails, it pumps less and less efficiently. Since the heart's activity is based on electrical impulses, soft-electronic materials that can be shaped around the organ hold promise to bolster the faltering activity of a failing heart. Hyeon’s groups took inspiration from recent work in which scientists transplanted a pig heart into a human. Although the patient survived only three months, it showed that pig hearts, which are similar to human hearts, can be used for experiments on soft-electronic materials.
Hyeon’s collaborative group first developed a stretchable, conductive cardiac mesh out of silver nanowires impregnated in rubber. They placed it on a rat heart, and showed the material could be used to pump blood over 50% more efficiently than the heart itself. Silver oxidizes easily, and the oxidized coating is not only toxic, it does not conduct. The group solved that problem by coating the wire with inert gold. They then wrapped the meshes around a pig heart. They were able to pinpoint areas where the heart was having problems, and apply electricity where it was needed.
Hyeon has many other irons in the fire, including the development of a photocatalytic enzyme that splits water to produce hydrogen. Current hydrogen production technologies are environmentally unfriendly, so his group is developing a catalyst that mimics the activity of a bacterial hydrogenase.
How does Hyeon manage such a wide variety of research projects? Collaboration, he said. “You cannot do it all.”
Other than his work, Hyeon's other passion is tennis. “I'm either in my office or on the tennis court,” he said.
Symposium X—MRS/The Kavli Foundation Frontiers of Materials features lectures aimed at a broad audience to provide meeting attendees with an overview of leading-edge topics.