Graduate student Jin Suntivich, lead author of the Nature Chemistry paper, holds up an electrochemical cell used for catalyst testing.
CAMBRIDGE, US: MIT researchers have found a new way to predict which materials will perform best as catalysts for oxygen reduction, a core process in metal air batteries and fuel cells, opening up the possibility of faster and more effective development of new high-efficiency, low-cost energy-storage technologies.
Such catalysts are the crucial materials that govern the performance of fuel cells as well as air-breathing batteries. So far, selecting and testing such materials has essentially been a matter of trial and error and most of the high-performing materials found have been rare and expensive, such as palladium and platinum.
The new principle, by contrast, should allow rapid assessment of a range of alternative catalysts made of metal-oxide materials, many of which are made of inexpensive and abundant elements.
The MIT researchers’ analysis found that the effectiveness of different materials could be determined by the arrangement of electrons in the outer shells of their atoms and the way surface metal ions bond to oxygen. The research - led by Yang Shao-Horn, Associate Professor of mechanical engineering and materials science and engineering at MIT and Hubert A Gasteiger, a Visiting Professor at MIT and a Chemistry Professor at the Technische Universität München in Garching, Germany -was published June 13 in the journal Nature Chemistry. Graduate student Jin Suntivich of MIT’s Department of Materials Science and Engineering is the lead author and John B Goodenough of the University of Texas at Austin is a co-author.
Shao-Horn said, “For some time, we knew that platinum was good” as a catalyst, but it was unclear whether the explanation could be applied to other materials such as metal oxides.
Research pioneered by Jens Nørskov and colleagues at Stanford University and Denmark Technical University established a simple parameter. This principle explains why certain metals perform better than others and it turns out that platinum just has the right electronic structure to provide optimum binding of oxygen - and thus high catalytic activity.
Now, “We have a theoretical framework and experimental evidence that explains why,” certain metal oxides perform better than others, said Shao-Horn.
The new work now makes it possible to screen thousands of candidate metal-oxide materials without the time-consuming tests needed to prove their exact performance. A material’s behaviour can now be predicted from a single parameter: how its electrons are distributed in the orbitals responsible for the bonding of metal to oxygen.
Robert Savinell, the George S. Dively Professor of Chemical Engineering at Case Western Reserve University, says this work is “Of high quality in rigour and innovation.” He adds that it “Allows for optimizing chemical compositions for other important catalyst characteristics such as ease of synthesis, durability,” and other qualities. He says the research results will have an impact on searches for catalyst materials “for alkaline fuel cells, metal-air batteries, and even for electrolysis cells [that] … will be important for converting renewable energy sources such as wind and solar to hydrogen for energy storage or for use in fuel cells for transportation.”
The research was sponsored by and done in collaboration with Toyota Motor Company, because of its potential to lead to better materials for electric car batteries. It also received support from the US Department of Energy’s Hydrogen Initiative, the National Science Foundation, the Chesonis Family Foundation, the Robert A Welch Foundation and the Office of Naval Research.
(C) MIT News Office