|A look at the sputter system at the RUB, with which the material libraries were manufactured. Credit: Christian Nielinger
The number of options makes it difficult to find promising materials. A German-Danish team has developed an efficient method for this.
Efficient electrocatalysts are hidden in materials that are composed of five or more elements, which are used, for example, for the production of green hydrogen. A team from the Ruhr University Bochum (RUB) and the University of Copenhagen has developed an efficient method to find the promising candidates in the countless possible materials. The researchers combined experiments and simulation. They report in the magazine "Advanced Energy Materials."
Millions of systems are conceivable
High entropy alloys, or HEAs for short, are chemically complex materials that consist of mixtures of five or more elements. The interesting thing about them is that they offer completely new opportunities for the development of electrocatalysts. These are urgently needed to make energy conversion processes more efficient, for example for the production and use of green hydrogen. "The problem with HEAs is that in principle millions of high entropy systems are possible and each system contains tens of thousands of different compositions," explains Prof. Dr. Alfred Ludwig, who heads the Materials Discovery and Interfaces chair at the RUB. This complexity can hardly be overcome with conventional methods and traditional high-throughput methods.
Five sources, six constellations
In their work, the researchers describe a new method that is intended to help find promising high-level crop alloys for electrocatalysis. In the first step, the team developed a way to create as many potential compositions as possible. For this, the researchers used a sputtering system that simultaneously applies the five raw materials involved to one carrier. "You can think of it as five spray cans that are aimed at one point of the goal," explains RUB researcher Dr. Lars Banko. A very specific composition of the five starting materials is created at each point of the carrier. Since this composition is also influenced by the position of the sources of the starting materials, the research team changed them in the experiment. In the subsequent measurements, data from the manufacturing processes flowed into six different constellations of the sources.
The RUB electrochemistry team then examined the carriers coated in this way for their electrocatalytic activity and stability. "This enables us to identify trends in which places there are potential promising candidates," explains Dr. Olga Krysiak, first author of work with Lars Banko. In order to get even closer to the composition of the materials, the team compared this data from the experiment with a large simulation data set, which the researchers made available to the University of Copenhagen. The comparison between simulation and experiment makes it possible to advance to the atomic scale of electrocatalysts, to estimate the statistical arrangement of atoms on the material surface and to determine their influence on the catalytic activity.