Unlocking the full potential of single-atom catalysts — Nagoya University establishes new design principles

In electrochemical energy conversion technologies such as fuel cells, enhancing the activity of electrode catalysts and improving the efficiency of resource utilization are critically important challenges from the standpoints of both increased energy conversion efficiency and cost reduction. Single-atom catalysts, in which metal atoms are dispersed at the single-atom level, have attracted particular attention as the ultimate form of a catalyst capable of achieving 100% atomic utilization, since all metal atoms are theoretically able to participate in the reaction. However, a fundamental problem has persisted with conventional single-atom catalysts that use porous carbon supports: many of the active metal atoms are buried within micropores or at interfaces between particles, making it difficult for reactants and electrons to reach them, so the actual site utilization falls far short of the theoretical value.

A research team led by Distinguished Professor Yusuke Yamauchi of the Graduate School of Engineering, Nagoya University has established design principles for raising the active-site utilization of single-atom catalysts to nearly 100% and created a two-dimensional single-layer nanocarbon structure. They demonstrated that its performance in an oxygen reduction reaction matches or surpasses that of costly platinum catalysts. Their findings were published in Nature Communications.

The design approach utilizes metal-organic frameworks (MOFs)—in which metal atoms are uniformly coordinated with organic ligands at the atomic level—as ideal precursors for single-atom catalysts. Using a surfactant-assisted freeze-casting (SAFC) strategy, the researchers successfully assembled MOF nanoparticles into a single-layer two-dimensional arrangement along the growing ice-crystal interface. They further established a new materials fabrication method in which heat treatment, applied while preserving this ordered arrangement, converts the MOF-derived metal atoms (without causing them to aggregate) into a two-dimensional nanocarbon structure rich in mesopores with the atoms uniformly anchored in the plane.

This two-dimensional hierarchically porous structure dramatically improves electron transport and mass transport of reactants and products throughout the catalyst layer, making it possible to efficiently utilize even the single-atom active sites deep within the catalyst that previously could not contribute to the reaction. As a result, the site utilization of the MOF-derived single metal atoms reached approximately 99% in the oxygen reduction reaction under acidic conditions. The material demonstrated electrochemical performance surpassing not only conventional single-atom catalysts but also commercial platinum catalysts.

This approach is applicable not only to iron-based single-atom catalysts, but also to non-precious metal catalysts such as cobalt, nickel, and manganese, as well as to precious metal single-atom catalysts such as platinum. It is therefore expected to be developed as a versatile materials design strategy applicable to a wide range of electrochemical reactions.

Yamauchi commented: "Single-atom catalysts have long been materials that are 'theoretically ideal but never fully utilized in practice.' In this research, rather than simply increasing the number of active sites, we returned to the fundamental question of how many of the existing active sites can actually be made to participate in the reaction, and tackled that problem head-on through structural design. By converting MOFs used as precursors into two-dimensional structures, and further transforming them into carbon materials through spatial control, I believe we have demonstrated that atomic-level functionality can be drawn out to the fullest extent across the entire material."

Journal Information
Publication: Nature Communications
Title: Near-100% site utilization of single atoms for efficient electrocatalysis
DOI: 10.1038/s41467-025-67756-8