When searching for catalysts for the energy transition, materials consisting of at least five elements — so-called high-entropy alloys (HEAs) — are considered highly promising. But to find the right combination of elements and composition ratios needed for the best activity is difficult, since there are theoretically millions of possibilities. To help speed the discovery of better electrocatalysts, a research team, led by professor Alfred Ludwig, head of the Materials Discovery and Interfaces Department (MDI) at Ruhr University Bochum (Germany; www.rub.de), has succeeded in producing microscale combinatorial libraries of all possible combinations of five elements on a carrier in a single step. The researchers also developed a method to analyze the electrocatalytic potential of each of the combinations in this micromaterial library in high throughput.
As described in a recent issue of Advanced Materials, the researchers were able to create microlibraries for two HEA systems: Ru–Rh–Pd–Ir–Pt and Co–Ni–Mo–Pd–Pt. They also were able to find the optimal combinations of elements in these HEAs for the three important electrocatalytic reactions: the hydrogen evolution reaction (HER), the oxygen evolution reduction reaction (ORR) and the oxygen evolution reaction (OER).
Source: Lars Banko, Ruhr-Universität Bochum
To create the microlibraries, the researchers used a process that combines co-sputtering with a shadow-masking technique, which enabled all combinations of the five elements to be fabricated onto a single carrier. Each individual material mixture appears as a 100-µm dia. spot on the carrier (photo). To study these material libraries, a technique known as scanning electrochemical cell microscopy was used. This involves measuring the electrochemical properties of the material at a specific point via a hanging nanodroplet of an electrolyte.
The technique promises to help chemists quickly discover promising catalysts for further study.