A newly developed pentanuclear iron complex (Fe5-PCz(ClO₄)₃) can offer an efficient, stable, and cost-effective solution for water oxidation. By electrochemically polymerizing the complex, researchers from Institute of Science Tokyo obtained a polymer-based catalyst, poly-Fe5-PCz, and achieved water oxidation with up to 99% Faradaic efficiency and exceptional stability, even under rigorous conditions. This breakthrough offers a scalable alternative to rare metal catalysts, advancing hydrogen production and energy storage for renewable energy.
Water oxidation plays a vital role in renewable energy technologies, especially in hydrogen production and artificial photosynthesis. By splitting water into oxygen and hydrogen, it provides a clean, sustainable energy source. However, replicating the efficiency and stability of natural photosynthetic systems in artificial catalytic setups—especially in aqueous environments—remains a significant challenge. Catalysts based on rare and expensive metals like ruthenium have shown high activity for water oxidation but are not practical for large-scale use due to their cost and limited availability.
To address this, a team of researchers led by Professor Mio Kondo from Institute of Science Tokyo (Science Tokyo), Japan, developed a more sustainable and cost-effective catalytic system using abundant metals. Their findings were published in Nature Communications on [Date].
The study introduces a novel pentanuclear iron complex, Fe5-PCz(ClO₄)₃, which possesses a multinuclear-complex-based catalytically active site and precursor moieties for charge transfer sites. Kondo explains, "By electrochemically polymerizing this multinuclear iron complex, we create a polymer-based material that enhances electrocatalytic activity and long-term stability. This approach combines the benefits of natural systems with the flexibility of artificial catalysts, paving the way for sustainable energy solutions."
The researchers synthesized the Fe5-PCz(ClO₄)₃ complex using organic reactions like bromination, nucleophilic substitution, Suzuki coupling reactions, and subsequent complexation reactions. The synthesized complex was characterized by mass spectrometry, elemental analysis, and single-crystal X-ray structural analysis. The researchers then modified glassy carbon and indium tin oxide electrodes by polymerizing Fe5-PCz using cyclic voltammetry and controlled potential electrolysis to afford a polymer-based catalyst, poly-Fe5-PCz. The charge transfer ability and electrocatalytic performance of poly-Fe5-PCz were evaluated through electrochemical impedance spectroscopy and oxygen evolution reaction (OER) experiments with oxygen production quantified by gas chromatography, respectively.
The results were highly promising. Kondo explains, "Poly-Fe5-PCz achieved up to 99% Faradaic efficiency in aqueous media, meaning nearly all the applied current contributed to the OER. The system also exhibited superior robustness and a reaction rate under rigorous testing conditions compared to relevant systems. Additionally, poly-Fe5-PCz demonstrated enhanced energy storage potential and improved electrode compatibility, making it suitable for a wide range of renewable energy applications." Its high stability was further confirmed by long-term controlled potential experiments, a key advantage for hydrogen production and energy storage technologies.
The study's findings have significant implications for sustainable energy. The use of iron—an abundant, non-toxic metal—ensures the system is both eco-friendly and cost-effective, offering a viable alternative to precious metal-based catalysts. Its stability under operational conditions addresses a major challenge in artificial catalytic systems, where long-term catalyst degradation often limits performance. Moreover, the system's performance in aqueous environments makes it suitable for applications in water splitting.
"Optimizing poly-Fe5-PCz synthesis and scalability could further enhance its performance, paving the way for industrial-scale hydrogen production and energy storage. Our study opens new possibilities for integrating the system into broader energy technologies, paving the way to a more sustainable future," concludes Kondo.
About Institute of Science Tokyo (Science Tokyo)
Institute of Science Tokyo (Science Tokyo) was established on October 1, 2024, following the merger between Tokyo Medical and Dental University (TMDU) and Tokyo Institute of Technology (Tokyo Tech), with the mission of "Advancing science and human well-being to create value for and with society."
