The core of the problem is chloride. Seawater carries a high concentration of chloride ions, and at the cathode of a seawater air battery these ions behave as aggressive interlopers. They adsorb onto the very metal centers that are supposed to bind oxygen intermediates, blocking active sites, degrading catalytic performance and accelerating the corrosion of the catalyst layer itself. Iron-based single-atom catalysts, prized for their high intrinsic oxygen reduction activity in alkaline conditions, are particularly vulnerable. The result is a painful trade-off: catalysts that are highly active on the bench tend to lose their edge quickly in real seawater, while corrosion-resistant materials are often too sluggish to deliver competitive power.

The Hainan University group, led by corresponding author Peng Rao, approached this dilemma with a concept they describe as p-d orbital hybridization. Instead of leaving iron atoms to fend for themselves on a carbon support, the researchers paired each iron active site with an adjacent tin atom, creating what is known as a dual single-atom catalyst. Tin, a p-block element with its own distinct orbital character, does not simply sit nearby as a passive neighbor. Through overlap between its p orbitals and the d orbitals of iron, it reshapes the local electronic structure of the iron center, tuning how strongly the site binds oxygen-containing intermediates and how hospitably it treats chloride ions in the surrounding electrolyte.

This electronic engineering addresses a well-known limitation of conventional iron sites. In many iron-nitrogen-carbon catalysts, the binding of oxygen reduction intermediates is too strong, meaning that reaction intermediates such as hydroperoxyl species linger on the surface longer than they should and slow the overall turnover of the catalyst. The Fe-Sn interaction weakens this overly strong adsorption into a more favorable intermediate regime, while simultaneously creating a locally negatively charged interface around the iron site. Because chloride ions are negatively charged, that charged microenvironment electrostatically discourages them from approaching and poisoning the active center. In effect, the catalyst builds a nanoscale fence around its most valuable atom.

The design did not emerge by guesswork. The team first carried out density functional theory calculations, comparing several candidate pairings of iron with different p-block metals in dual-site configurations. Among the candidates, the iron-tin combination stood out with the best balance between oxygen reduction activity and chloride resistance, providing the theoretical justification for an ambitious synthesis. The researchers then produced the material using what they call a movable-type printing strategy, a modular approach that positions the two metal precursors with atomic precision on a nitrogen-doped carbon support before activation locks them into place.

Advanced characterization confirmed that the synthesis had achieved its goal. Microscopy and X-ray spectroscopy showed that both iron and tin were atomically dispersed across the carbon framework, stabilized as adjacent dual single-atom sites rather than clustering into nanoparticles. That atomic dispersion matters enormously. It maximizes the density of accessible active sites, ensures that every iron atom benefits from a tin neighbor, and prevents the formation of larger metal particles that could serve as initiation points for corrosion in the harsh chloride-rich environment.

Electrochemical testing in alkaline seawater electrolyte delivered striking results. The FeSn dual single-atom catalyst achieved a half-wave potential of 0.900 volts versus the reversible hydrogen electrode, outperforming both single-metal iron and tin catalysts prepared in the same way and beating commercial platinum-on-carbon, the traditional benchmark for oxygen reduction. The catalyst followed a near four-electron oxygen reduction pathway, the most efficient route that converts oxygen directly to hydroxide and delivers the maximum possible cell voltage. Equally important for real deployment, the material showed negligible activity decay after 30,000 accelerated durability test cycles, a punishing stress test that simulates years of charge-discharge operation.

Perhaps the most convincing evidence came from post-mortem analysis. After extended testing in the chloride-laden electrolyte, X-ray photoelectron spectroscopy revealed no observable iron-chloride signal on the catalyst surface, indicating that chloride adsorption on the iron active sites had been effectively suppressed throughout the testing period. This directly validates the design hypothesis: the negatively charged microenvironment generated by the Fe-Sn electronic interaction had done its job, keeping the poison away from the active center even as the catalyst worked hard for tens of thousands of cycles.

“For seawater batteries, activity alone is not enough,” said Peng Rao, the corresponding author of the study. “The catalyst also needs to drive oxygen conversion efficiently while resisting chloride-induced poisoning. The Fe-Sn dual-site structure gives us a way to combine these two functions at the atomic level.” The quote captures the central lesson of the work: in marine electrochemistry, selectivity against chloride is not an optional extra but a design requirement on par with activity itself.

The practical payoff was demonstrated when the catalyst was assembled into flow-type seawater air batteries. Devices built with the FeSn dual single-atom catalyst reached a peak power density of 255.6 milliwatts per square centimeter, higher than comparable cells based on platinum-on-carbon or the iron-only single-atom catalyst, and operated stably for more than 500 hours under the reported testing conditions. That combination of high power and long endurance in a realistic seawater-fed architecture suggests the material is ready to be taken seriously for marine energy systems rather than remaining a laboratory curiosity.

Beyond the immediate application, the study positions p-d orbital engineering as a general strategy for designing electrocatalysts that must simultaneously deliver high activity and resist chloride attack. Many reactions of interest in seawater electrochemistry, from oxygen evolution to chlorine-tolerant hydrogen production, face the same fundamental challenge of selective chemistry in an ionically aggressive medium. If pairing active transition-metal sites with judiciously chosen p-block partners proves general, the design principle demonstrated here could extend well beyond iron and tin, and well beyond oxygen reduction.

The research, published in Science Bulletin, arrives at a moment of growing investment in ocean-based energy infrastructure. Offshore wind farms, autonomous underwater systems and remote marine sensors all need durable storage, and seawater batteries are among the few options whose electrolyte comes free with the deployment site. By showing that a simple atomic partnership, one iron atom and one tin atom held in place on a carbon support, can defuse the corrosive chemistry of the ocean while accelerating the very reaction the battery depends on, the Hainan University team has moved the field a meaningful step closer to seawater batteries that survive, and thrive, in the environment they are built to harness.

Subject of Research: Development of an iron-tin dual single-atom catalyst using p-d orbital hybridization to improve oxygen reduction activity and chloride resistance in seawater batteries

Article Title: How can seawater batteries survive chloride corrosion?

Article References: How can seawater batteries survive chloride corrosion?. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: seawater batteries, oxygen reduction reaction, dual single-atom catalyst, chloride corrosion, p-d orbital hybridization, iron-tin catalyst, electrocatalysis, alkaline electrolyte, marine energy storage, density functional theory, nitrogen-doped carbon, air cathode

The new technology centers on the concept of a yarn-like battery that operates efficiently when submerged in seawater. The groundbreaking research is documented in the journal "ACS Applied Materials and Interfaces," presenting an exciting opportunity for integrating energy solutions into everyday marine life. This prototype adapts to its environment, providing electricity for lighting fishing nets, powering life jackets, and energizing mooring lines, enabling a range of potential applications that span from safety gear to innovative maritime technology.

At the core of this development is the use of materials that are both flexible and conductive, forming the backbone of this new electrochemical technology. Researchers have successfully exploited the natural properties of seawater, which contains essential ions that facilitate electrical conduction, making it an ideal electrolyte for battery operation. In this unique application, the battery’s electrodes were composed of carbon fiber, treated with advanced conductive coatings to maximize power output while ensuring structural integrity.

Using the electrically conductive coatings, the team designed a positive electrode (or cathode) using nickel hexacyanoferrate and a negative electrode (anode) constructed from polyamide material. The combination of these materials allows the battery to store and release energy efficiently even under the corrosive influence of saltwater. The subsequent twisting of these two electrode components into a yarn-like structure enhances their flexibility, enabling the battery to adapt to various shapes and forms—the very essence of modern wearable and weaveable technology.

A remarkable achievement of this work lies in the manufacturing process of the seawater battery, which involves intricate layering techniques. The cathode string is wrapped in a durable layer of fiberglass, ensuring protection from environmental conditions while still allowing seawater accessibility. The researchers then encased the entire assembly in a nonwoven, permeable fabric, which serves a dual purpose of safeguarding the electrodes while facilitating interaction with the salty electrolyte.

Performing extensive tests, the prototypes demonstrated exceptional resilience and stability. After undergoing rigorous bending operations—over a remarkable capacity of 4,000 bends—the battery retained its charge, proving its mechanical and electrical durability. This performance indicates a future where batteries are not only integrally embedded in textiles but can also withstand the physical rigors of a marine environment.

Further evaluations in seawater showcased that the battery sustained its initial charging efficiency and electricity storage capacity over an impressive 200 charge and discharge cycles. These findings illustrate not only the feasibility of integrating energy technologies into marine applications but also the potential for developing a new class of batteries that provide sustainable energy solutions without sacrificing flexibility or reliability.

As part of their proof-of-concept, the researchers demonstrated practical applications of their innovation by knotting battery strands to create a fishing net filled with energy-storing capabilities. Following a soak in seawater for electrolyte absorption, the net was successfully charged and utilized to power a panel of ten LEDs. Similarly, a rectangular fabric sample was immersed in a sodium sulfate solution, demonstrating the battery’s functionality for over an hour, a promising capability for various marine scenarios.

The potential uses for this technology are groundbreaking. Envisioning its application in fishing nets and safety gear opens up a world of possibilities for harnessing renewable energy sources that can change the face of maritime operation and safety standards. This yarn-like battery blends seamlessly into the fabric of everyday marine activities, bringing forth innovations that ensure both efficiency and safety for explorers, fisherfolk, and maritime security personnel alike.

Such products could revolutionize the collaboration of technology and nature, enabling not just a sustainable approach to energy, but also contributing to safer marine conditions. Fishing nets equipped with these energy-storing capabilities could illuminate underwater activities, enhancing safety for nighttime operations while sustaining an eco-friendly profile that aligns with environmental conservation efforts.

In a world increasingly conscious of the environmental impact, this research highlights a forward-thinking approach to utilizing abundant natural resources. By capitalizing on the saltiness of seawater, a readily available and sustainable material, the researchers present a compelling argument for shifting the paradigm around energy storage. The marine version of a rechargeable battery epitomizes the potential for innovation by integrating advanced materials science with practical applications, fostering a brighter future ahead.

The broader implications extend beyond the marine landscape, as these advancements may influence the development of similar technologies for other adaptable, flexible electrical needs in our evolving society. As the integration of electronics into textiles and everyday objects becomes more prominent, these pioneering efforts reaffirm the trajectory toward a greener and smarter future.

Ultimately, the researchers have not only acknowledged the funding sources that supported this compelling project but heralded a new era in energy solutions. The collaboration among academic, governmental, and sport administration institutions demonstrates a unified push toward progress, aspiring to enlighten and power our world through innovation and scientific inquiry.

This revolutionary development suggests that future generations need not depend solely on traditional, rigid battery solutions. Instead, they could benefit from a world where energy is seamlessly integrated into the very fabric of their daily lives, providing not just portable solutions but also a pathway toward sustainability that respects the natural environment.

This collaboration of interdisciplinary efforts could be the catalyst that ignites further innovations in battery technology, ensuring that humanity stays ahead of energy needs while minimizing environmental impact.

As the journey of this innovative seawater battery advances, further study and application will undoubtedly draw attention, inspiring a tidal wave of interest in the safe, efficient, and flexible battery solutions needed for the future of energy consumption and sustainability.

Subject of Research: Seawater-compatible yarn-like batteries for marine applications.
Article Title: “Constructing High-Performance Yarn-Shaped Electrodes via Twisting-after-Coating Technique for Weavable Seawater Battery”.
News Publication Date: 11-Dec-2024.
Web References: ACS Journal.
References: DOI: 10.1021/acsami.4c16439.
Image Credits: Adapted from ACS Applied Materials & Interfaces 2024.

Keywords

Batteries, Seawater, Flexible Electronics, Electrodes, Marine Applications, Electrochemistry, Textile Engineering, Renewable Energy, Sustainable Technology.