Protonic ceramic electrochemical cells, or PCECs, occupy a special place in the clean energy landscape because of their dual functionality. Within a single system, they can operate as fuel cells, converting hydrogen into clean electricity without producing pollutants, or as electrolyzers, using electricity to split water into hydrogen fuel. This reversible operation makes them unusually versatile candidates for applications ranging from grid-scale energy storage to hydrogen refueling infrastructure. Equally important is their operating temperature. Unlike conventional ceramic electrochemical devices that often require very high temperatures to function efficiently, PCECs can deliver strong performance at relatively lower temperatures, which reduces material stress, cuts operating costs, and simplifies engineering requirements.

Yet for all their promise, PCECs have been held back by a problem that is invisible to the naked eye. In a typical cell, the electrolyte is a dense, smooth ceramic layer, while the electrode is a porous, sponge-like structure. When these two components are brought together, they do not form perfect physical contact across their entire shared surface. Instead, only a fraction of the interface is genuinely touching. The gaps that remain act as barriers to the flow of charge, creating what engineers call interfacial contact resistance. This resistance prevents the materials from realizing their intrinsic performance, meaning that even the most advanced electrode and electrolyte chemistries can be undermined by a poorly connected interface.

To understand precisely how this contact problem governs cell behavior, the SKKU team took an unusually rigorous approach. Rather than simply trying a fix and measuring the result, they fabricated experimental model cells with varying degrees of contact between the electrode and the electrolyte and subjected them to detailed analysis. The goal was to isolate the relationship between contact and resistance. The results were strikingly systematic: interfacial resistance decreased in a well-defined pattern as the proportion of the two components that were actually in physical contact increased. The researchers formalized this proportion as a metric they call contact coverage, and in doing so they elevated it from a vague qualitative concern to a quantified design parameter that directly determines cell performance.

Identifying contact coverage as a key variable was only half the challenge. The team then needed a practical way to maximize it in real devices, where the mismatch between a dense smooth surface and a porous rough one is inherent to the architecture. Their solution came in the form of electrostatic spray deposition, a fabrication technique that harnesses electrostatic forces to propel microscopic liquid droplets onto a surface with exceptional uniformity. Using ESD, the researchers deposited an extremely thin and dense interlayer, measured on the nanometer scale, uniformly across the electrolyte surface. This precursor-derived interlayer conforms to the underlying topography and bridges the gap between the two components, dramatically increasing the effective contact area at the electrode-electrolyte interface.

The performance consequences were immediate and substantial. Cells incorporating the nanoscale interlayer demonstrated markedly improved output over conventional cells in both of the device’s operating modes. In power generation mode, where the cell functions as a fuel cell converting hydrogen into electricity, the enhanced interface allowed charge to move more freely across what had previously been a bottleneck. In hydrogen production mode, where the cell operates as an electrolyzer, the same improvement applied. The fact that a single interfacial modification benefits both modes underscores the central role that contact resistance plays in the overall performance envelope of these reversible devices, and it suggests that interface engineering can deliver compounding returns across the hydrogen value chain.

Efficiency alone, however, is not enough for a technology aiming at commercial deployment, and durability has long been a parallel concern. The coated cells maintained stable operation under harsh conditions involving rapid temperature changes, a demanding test for ceramic devices because thermal cycling can strain and even delaminate the interfaces between dissimilar components. The team attributes this resilience to the strong adhesion between the electrode and the electrolyte that the nanoscale interlayer provides. By serving as a robust bonding layer as well as a conductive bridge, the coating addresses mechanical integrity and electrical performance simultaneously, a combination that is often difficult to achieve with conventional fabrication approaches.

The versatility of the technology extends to the fuels themselves. While hydrogen remains the headline fuel of the emerging hydrogen economy, the SKKU cells exhibited excellent performance and stability when directly fueled with methane or ammonia, two energy carriers that are attracting significant attention as next-generation alternatives. Direct fuel flexibility matters because transporting and storing pure hydrogen remains logistically challenging, and molecules such as ammonia are far easier to handle at scale. A cell that can accept these fuels without sacrificing performance or durability widens the practical pathways for deployment in sectors where hydrogen infrastructure does not yet exist.

Just as important for commercialization is the question of scale. Laboratory breakthroughs in energy materials frequently falter when engineers attempt to move from small, carefully controlled samples to the large-area components required for real products. The ESD process used by the SKKU team enabled uniform fabrication on large-area substrates, demonstrating that the interlayer technique is compatible with industrial-scale manufacturing rather than confined to the laboratory bench. Scalability, combined with the relatively modest thermal requirements of PCECs, positions the technology for meaningful industrial translation.

Professor Lee framed the significance of the work in terms that reach beyond a single device class. No matter how advanced a new material may be, it cannot deliver its full performance if the interfaces between components are not properly connected, he noted, emphasizing that the study quantitatively defines microscopic contact behavior while simultaneously maximizing both cell performance and durability through a scalable precision nano-process. He added that the team expects the technology to be widely applicable to large-scale clean energy power plants, hydrogen-powered vehicles, eco-friendly energy storage systems, and many other fields. The research was supported by grants from the National Research Foundation of Korea funded by the Ministry of Science and ICT and the Ministry of Environment, together with the Institutional Research Program of the Korea Research Institute of Chemical Technology, reflecting the strategic priority that Korea places on hydrogen technologies. As the global race to decarbonize intensifies, the study is a reminder that in electrochemistry, as in so much of engineering, the smallest details, in this case a nanometer-thin layer where two materials meet, can determine whether a promising technology finally performs up to its theoretical potential.

Subject of Research: Interface nanocoating to reduce contact resistance in protonic ceramic electrochemical cells for hydrogen production and power generation

Article Title: SKKU research team boosts hydrogen cell efficiency and durability via innovative interface nanocoating

Article References: SKKU research team boosts hydrogen cell efficiency and durability via innovative interface nanocoating. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: protonic ceramic electrochemical cells, hydrogen, fuel cells, electrolyzers, interfacial contact resistance, nanocoating, electrostatic spray deposition, interface engineering, clean energy, electrolyte, electrode, Sungkyunkwan University