A study led by UCLA researchers developed a method for predicting platinum alloys’ potency and stability—two key indicators of how they will perform as catalysts in hydrogen fuel cells. Then, using that technique, they designed and produced an alloy that yielded excellent results under conditions approximating real-world use. The findings are published in the journal Nature Catalysis.
A critical technological roadblock to the widespread adoption of proton-exchange membrane fuel cells is the development of highly active and durable platinum-based catalysts for accelerating the sluggish oxygen reduction reaction, which has largely relied on anecdotal discoveries so far. While the oxygen binding energy ∆EO has been frequently used as a theoretical descriptor for predicting the activity, there is no known descriptor for predicting durability.
Here we developed a binary experimental descriptor that captures both the strain and Pt transition metal coupling contributions through X-ray absorption spectroscopy and directly correlated the binary experimental descriptor with the calculated ∆EO of the catalyst surface. This leads to an experimentally validated Sabatier plot to predict both the catalytic activity and stability for a wide range of Pt-alloy oxygen reduction reaction catalysts. Based on the binary experimental descriptor, we further designed an oxygen reduction reaction catalyst wherein high activity and stability are simultaneously achieved.—Huang et al.
Huang et al.
Fuel cells generate power using oxygen from the atmosphere and hydrogen. A key step in the process is using a catalyst to break the bonds between pairs of oxygen atoms. The catalysts that work best are highly active, in order to drive the reaction, while also being stable enough to be used for long periods of time. And for those designing fuel cells, finding the best catalysts has been a major challenge.
Platinum is the best element for the purpose, but its rarity makes the technology prohibitively expensive for large-scale adoption. An alloy combining platinum with a more readily accessible metal or metals would reduce the cost, but there has never been a practical, real-world method for quickly screening which alloy would make the best catalyst. As a result, advances in the technology have come through trial and error so far.
This is a decisive step forward toward the rational design, down to the microscopic scale, of catalysts with optimal performance. Nobody has ever come up with a method, either theoretical or experimental, to predict the stability of platinum alloy catalysts.—Alessandro Fortunelli of Italy’s National Research Council, co-corresponding author
The new method predicts both the potency and the stability of platinum alloy catalysts. It was developed using a combination of experiments, complex computation and X-ray spectroscopy, which allowed the investigators to precisely identify chemical properties.
The researchers then created catalysts combining precise amounts of platinum, nickel and cobalt in a specific atomic structure and configuration based on their experimental measure. They showed that the alloy they designed is both highly active and highly stable, a rare but much-needed combination for fuel cell catalysts.
Co-corresponding author Yu Huang, a professor of materials science and engineering at the UCLA Samueli School of Engineering, said that the method could be applied to potential catalysts mixing platinum with a subset of metals beyond nickel and cobalt.
The paper’s other co-corresponding authors are chemist Qingying Jia of Northeastern University and theorist William Goddard of Caltech. Huang, whose UCLA laboratory was primarily responsible for designing and testing the catalyst, said the collaboration with scientists and engineers at other institutions was vital to the study’s success.
Huang’s group is now collaborating with Toyota Motor Corp. to develop fuel cell catalysts with possible real-world applications.
The research was supported by the US Office of Naval Research and the National Science Foundation.
Huang, J., Sementa, L., Liu, Z. et al. (2022) “Experimental Sabatier plot for predictive design of active and stable Pt-alloy oxygen reduction reaction catalysts.” Nat Catal 5, 513–523 doi: 10.1038/s41929-022-00797-0