Researchers Reveal Versatile Role of Silver Nanocatalyst in Solid Oxide Cells

In a groundbreaking study, researchers have found that the same silver (Ag) nanocatalyst can operate at different reaction sites depending on whether a solid oxide cell is generating electricity or producing hydrogen. This discovery offers a novel approach to designing next-generation energy devices for enhanced performance, led by Professors WooChul Jung and Jeong Woo Han from the Department of Materials Science and Engineering at Seoul National University (SNU), alongside teams from KAIST and the Korea Basic Science Institute (KBSI).

Understanding Solid Oxide Cells

Solid oxide cells facilitate the movement of oxygen ions through solid materials to perform dual functions: generating electricity or splitting water to produce hydrogen. Their versatility positions them as a key technology in the clean energy and hydrogen sectors, with potential applications in combined heat and power systems and renewable energy-driven hydrogen production.

The significance of the findings has been acknowledged in the prestigious journal Energy & Environmental Science, where it has been featured as an Outside Back Cover article.

Insights into Catalytic Mechanisms

The study emphasizes the crucial role of oxygen reactions at the air electrode in determining the performance and durability of solid oxide cells. However, the complex structures of real electrodes have often obscured the precise roles of nanocatalysts during these reactions.

The researchers created model electrodes with precisely controlled structures, utilizing metal nanoparticles such as silver, cobalt, palladium, and platinum, deposited on thin film perovskite oxide electrodes. Among these, silver demonstrated the most significant catalytic enhancement.

Reaction Sites and Their Variability

Further investigations into the size and arrangement of silver nanoparticles revealed distinct reaction sites depending on operational mode. During the oxygen reduction reaction linked to electricity generation, increased reaction rates corresponded with larger boundary lengths between silver nanoparticles and the electrode. However, during oxygen evolution for hydrogen production, the surface area of silver nanoparticles became the critical reaction zone.

This indicates that the same nanocatalyst plays essential roles in two different locations based on the cell’s operating direction. By adjusting applied voltage and oxygen concentration, the researchers determined that silver nanocatalysts facilitate electron transfer during oxygen reduction, while aiding in the assembly and release of oxygen molecules during evolution.

Atomic-Level Analysis and Future Implications

Synchrotron-based analysis coupled with atomic theoretical calculations further illuminated how silver nanocatalysts modify the electronic structure of electrode surfaces, enhancing favorability for oxygen reduction and facilitating the joining of oxygen atoms during evolution.

The findings suggest a transformative design strategy for solid oxide cells. Instead of optimizing nanocatalysts as singular components, there is potential for separate engineering of catalyst surfaces and electrode interfaces, which may significantly improve efficiency in distributed energy systems and reduce electricity demands for renewable energy-powered electrolysis.

Professor WooChul Jung remarked on the substantial contributions of the research, highlighting its ability to quantitatively evaluate nanocatalyst performance and identify their operational sites and mechanisms. The study establishes a framework for future investigations into energy conversion materials and catalytic systems.

Supported by the Ministry of Science and ICT and the National Research Foundation of Korea, this research marks a step forward in the ongoing exploration of high-efficiency energy conversion technologies.