In this article, a team of expert scientists explains why electrochemical interfaces are crucial enablers of sustainable energy technologies
The transition toward a future de-fossilised energy system is a global imperative. It hinges on technologies that are capable of converting renewably generated power into energy-rich chemicals for valorisation in e-fuels and e-chemicals, as well as in utilisation for energy logistics, i.e., for storage, mobility, distribution of large capacities of energy and converting this chemical energy back into electricity when needed.
Batteries, fuel cells and electrolysers in the energy transition
Batteries, fuel cells and electrolysers are the technological backbone of the energy transition. Despite their macroscopic appearance as robust industrial devices, their performance is determined by phenomena occurring within a region only a few angstroms thick: the electrochemical interface. Understanding, controlling, and optimising the structure and properties of the kinetic processes at this interface are central to improving the efficiency, cost-effectiveness, and durability of energy conversion technologies.
The electrochemical interface is formed at the contact of a solid electrode, usually a metal, with an ion-conducting electrolyte medium, such as a liquid electrolyte, a water-filled ionic polymer membrane, or a solid-state ionic conductor. Within the microscopic interface region, electrons supplied by a power source to the metal surface interact with ions that assemble on the electrolyte side to exactly balance the electronic excess charge.
The properties of the interface, the strength of electron-ion interactions and correlation effects are modulated by surface processes involving reactants such as hydrogen, oxygen, and water, which undergo adsorption, dissociation, and recombination. These processes determine the rates and pathways of key electrochemical processes, such as the oxygen reduction at platinum catalysts in fuel cells, or the oxygen evolution reaction at iridium catalysts – even less abundant or more critical than platinum – in electrolysers.
Although invisible at the macroscale, the interface entails an intricate landscape shaped by surface composition, electric fields, more or less ordered solvent layers, and dynamically formed reaction intermediates. Because the chemical environment here differs significantly from that of the surrounding bulk materials, even subtle changes in interfacial structure can markedly alter the effective rates at which reactions proceed. All meaningful electrochemical activity originates at this interface, making it the central determinant of device behaviour.
Why electrochemical interfaces matter
Electrochemical interfaces are fundamental to the overall performance of energy-conversion technologies such as fuel cells and electrolysers. When reaction intermediates bind too strongly or too weakly to the electrode, or when the interfacial environment restricts the movement of ions or the transfer of electrons, the device requires additional energy to drive the desired reaction. This is evident in fuel cells, where the slow kinetics of the oxygen reduction reaction limit the overall reaction rate, and water electrolysers, where the oxygen evolution reaction demands a significant overpotential, leading to an irreversible loss of energy or a reduction of the efficiency of the cell.
As a result, even marginal improvements in interfacial chemistry can translate directly into lower overvoltages, higher efficiencies, and reduced system costs. Bringing about these improvements is the mission of the fields of electrocatalysis and electrochemical engineering, with the goal of designing tailor-made electrocatalytic materials, electrodes, and whole devices that accelerate desired interface reactions while suppressing degradation processes that diminish their lifetime.
The interfaces of fuel cells and electrolysers must operate and survive under highly demanding conditions, including widely and rapidly varying electrode potentials, temperature fluctuations, strong oxidative species, and rapid gas evolution. Many degradation phenomena, such as catalyst dissolution, support corrosion, particle agglomeration or membrane thinning, originate within the interfacial region.
By understanding how local chemical conditions and mechanical stresses influence the rates of electrocatalytic processes and long-term stability, researchers can design metal- electrolyte interfaces that retain performance over thousands of operational hours, which is essential for commercial deployment in both mobility and stationary applications.
The nature of the electrochemical interface also influences the amount of precious metals (including critical raw materials such as platinum, iridium and others) required for efficient operation. Catalysts based on platinum-group metals remain the most effective for key reactions, but their scarcity presents a longstanding cost challenge. Research directed at improving interfacial properties helps reduce the amount of precious metal needed without compromising activity. This interface-driven approach not only lowers device costs but also enhances the long-term sustainability of the hydrogen sector.
Emerging and promising directions for electrochemical interface research
Progress in understanding electrochemical interfaces is being accelerated by high-throughput, advanced in-situ/operando characterisation methods, computational modelling, and machine-learning-guided materials discovery. These tools, cleverly combined, can help researchers visualise reaction intermediates, map degradation pathways, and accelerate the development of new catalyst materials and structures that exploit interfacial phenomena in unprecedented ways. At the same time, innovations in hierarchical electrode architectures, protective surface layers, and novel ionomers are reshaping how interfaces are engineered for advanced fuel cells and electrolysers.
Going beyond optimisation of the interface itself, it will become increasingly important to understand the science of the scale-up of their production to reduce costs, as well as to accelerate testing for reliable large-scale implementation . In the four Institutes of Energy Technologies (IET) at Forschungszentrum Jülich, we are tackling exactly these grand challenges with a team of more than 350 scientists and PhD researchers.
We combine interdisciplinary expertise from physics, chemistry, material science, chemical and process engineering, electrical and mechanical engineering, to understand, optimise and control interfacial phenomena from the nanoscale all the way to technical devices in the MW range.
Utilising our outstanding research infrastructures at FZJ, including the unique Ernst-Ruska centre for electron microscopy or the JUPITER supercomputing facility, as well as collaborating with industrial frontrunners like Siemens Energy, Bosch, BASF, or Schaeffler, we leverage our extensive knowledge to significantly advance electrochemical interfaces for energy conversion and storage devices.
As renewable energy technologies become more efficient, more stable, and more affordable, their large-scale commercial deployment will ramp up. By improving the fundamental understanding of electrochemical interfaces, the field is paving the way for fuel cell and electrolyser technologies that can operate more efficiently, last longer, and rely less on scarce materials. These advancements will be critical for enabling affordable renewable energy conversion, large-scale and long-term storage, and, finally, more resilient energy systems worldwide.
