A Korean research team has developed an eco-friendly cell design technology that can boost hydrogen production up to threefold by mixing multiple metals.
A research team led by Professor Lee Kang-taek of KAIST’s Department of Mechanical Engineering announced Monday that it developed a new “oxygen electrode material” that significantly improves cell reaction speed and output performance through an entropy-maximizing design. The oxygen electrode material is a core component that drives the oxygen evolution reaction during hydrogen production in a cell.
Among green hydrogen technologies that produce hydrogen from water without carbon emissions, the proton-conducting electrochemical cell (PCEC) is considered a key technology.
PCECs work by splitting water using electrical energy, with hydrogen ions moving through the cell interior to produce hydrogen. Despite high efficiency, however, the slow reaction speed at the internal oxygen electrode has limited performance improvements.
The research team focused on a “high-entropy” strategy that increases disorder by simultaneously introducing multiple metal elements. Normally, mixing many elemental substances causes instability. In the case of high-entropy phenomena, however, mixing more elements actually maintains a stable single-phase structure. By maximizing entropy at the right composition, hydrogen ions move more freely and reactions occur more easily inside the cell.
The team designed a “high-entropy double perovskite oxygen electrode” by simultaneously introducing seven metal elements — including Pr, La, Na, Nd, Ca, Ba and Sr — into the metal site (A-site) within the electrode structure.
This electrode is based on a “perovskite” structure in which metals and oxygen are arranged in a regular pattern. The team applied a high-entropy design mixing multiple elements into a “double structure” containing different metals. The diverse metals intermixing enhanced charge transfer and oxygen-related reactions inside the electrode, resulting in faster electricity generation and hydrogen production.
The team also confirmed through density functional theory (DFT) calculations that the oxygen vacancy formation energy was reduced by more than 60% compared with conventional materials. This means more reaction-capable spaces are created more easily inside the electrode. Hydrogen ion migration speed also increased more than sevenfold, accelerating the hydrogen generation process within the electrode.
The cell equipped with the new electrode maintained stability during prolonged use along with performance improvements. Experimental results showed it recorded a power density approximately 2.6 times higher (1.77 W cm⁻²) than conventional cells even at 650 degrees Celsius, and hydrogen production performance improved approximately threefold (4.42 A cm⁻²). The cell also showed only 0.76% performance degradation in a steam-condition test conducted over 500 hours.
“This research demonstrates that electrode reactivity can be controlled using the thermodynamic concept of entropy,” Professor Lee Kang-taek said. “It could significantly raise green hydrogen production efficiency and accelerate the commercialization of the hydrogen economy.”
The study was selected as the cover paper of Advanced Energy Materials, an international academic journal, and was published on December 16 last year.
