Silver nanocatalysts switch reaction sites between power generation and hydrogen production
For the first time, researchers have discovered that the same silver (Ag) nanocatalyst operates at different reaction sites depending on whether a solid oxide cell is generating electricity or producing hydrogen. This finding ...
A joint research team led by professors WooChul Jung and Jeong Woo Han from the Department of Materials Science and Engineering at Seoul National University (SNU), in collaboration with professor Sang Ouk Kim's team at KAIST and Dr. Beomgyun Jeong's team at the Korea Basic Science Institute (KBSI), has elucidated the operating mechanism of silver nanocatalysts that enhance the performance of solid oxide cells. The team confirmed that the sites and mechanisms of oxygen reactions vary depending on the cell's operating mode.
Solid oxide cells are next-generation energy devices that use the transport of oxygen ions to either generate electricity or split water to produce hydrogen. They are considered a key technology for expanding clean power generation and hydrogen use because they can be applied to a wide range of systems—from distributed combined heat and power systems in buildings and factories that generate electricity while using the high-temperature heat produced during operation to renewable energy–based green hydrogen production.
The findings were published in the journal Energy & Environmental Science (Impact Factor: 30.5) and were selected as an Outside Back Cover article, highlighting their significance.
The performance and lifespan of solid oxide cells are largely determined by the rate of oxygen reactions at the air electrode. However, because of the structural complexity of actual electrodes, it has been difficult to identify precisely where and how nanocatalysts contribute to these reactions. While previous studies established that metal nanocatalysts improve cell performance, it remained unclear whether catalytic activity primarily occurs on the catalyst surface or at the interface between the catalyst and the electrode. It was also unknown whether the catalysts operate in the same way during electricity generation and hydrogen production.
A visual representation of how metal nanocatalysts promote oxygen exchange reactions at solid oxide cell electrodes. Credit: Energy & Environmental Science
(Left) Schematic illustration of the fabrication process for a model platform with metal nanoparticle arrays formed on an electrode with a precisely controlled structure and composition. (Right) Microscopy images of platinum, palladium, cobalt, and silver nanoparticle arrays; an image of the silver–electrode interface; and morphologies of silver nanoparticle arrays with varying particle sizes. Credit: Energy & Environmental Science
Results show that the dominant reaction sites shift between the metal–electrode interface and the metal particle surface depending on the operating mode. Credit: Energy & Environmental Science
(Left) Synchrotron-based real-time analysis showing changes in the electrode's electronic structure during operation. (Right) Schematic illustration based on density functional theory calculations showing how silver nanoparticles raise the electrode's Fermi level to promote oxygen reduction. Credit: Energy & Environmental Science