Single-Layer RuO2 Catalyst Slashes Overpotential in Acidic Water Electrolysis

Green hydrogen has a stubborn bottleneck, and it sits at the anode. In a proton-exchange membrane (PEM) water electrolyser, the acidic oxygen-evolution reaction (OER) is so kinetically sluggish that a large extra voltage, the overpotential, must be applied before oxygen bubbles begin to form at any useful rate. That wasted energy translates directly into higher electricity bills and, ultimately, more expensive hydrogen. Now a team led by researchers at Soochow University, working with collaborators across China, Taiwan and Germany, reports in Nature Nanotechnology a catalyst design that attacks the problem at its structural root: a single-layer, edge-sharing form of ruthenium dioxide, known as 1T-RuO2, that delivers ultralow overpotential, exceptional activity and remarkable durability under the harsh acidic conditions that destroy most candidate catalysts.

The central insight of the study concerns how adjacent RuO6 octahedra, the basic building blocks of ruthenium dioxide, are connected to one another. Conventional rutile-type RuO2, the workhorse acidic OER catalyst, arranges its octahedra in corner-sharing and edge-sharing motifs that do not provide the most favorable electronic geometry. In the newly synthesized 1T phase, the octahedra share edges in a configuration that aligns the ruthenium 4d orbitals in parallel across neighboring clusters. This parallel alignment opens a highway for intersite electron transport: electrons generated during the four-proton, four-electron OER sequence can hop efficiently from one ruthenium center to the next rather than becoming localized at a single active site. The result is a catalyst in which electronic communication, rather than isolated site chemistry, becomes the rate-enhancing factor.

The performance numbers reported by the team are striking by any benchmark in the field. In acidic electrolyte, the 1T-RuO2 single layer requires an overpotential of just 77 millivolts to drive a current density of 10 milliamperes per square centimeter, a figure that places it among the most active acidic OER catalysts described to date. At a potential of 1.50 volts versus the reversible hydrogen electrode, the material achieves a mass activity of 3,743.43 amperes per gram of ruthenium and a turnover frequency of 23.99 per second, both substantially exceeding the corresponding values for rutile-RuO2 measured under the same experimental framework. These metrics matter because ruthenium, while cheaper than the iridium that currently dominates commercial PEM anodes, is still a precious metal; extracting more catalytic turnover per gram directly reduces the loading, and therefore the cost, of the precious metal in each device.

Activity alone has never been the hard part of acidic water oxidation. The acidic OER environment is brutally corrosive: highly oxidizing potentials, a flood of protons and reactive oxygen intermediates combine to dissolve most transition-metal oxides within hours. Ruthenium dioxide is comparatively robust, yet even it tends to degrade through ruthenium dissolution and lattice-oxygen-mediated pathways that corrode the catalyst from within. The durability demonstrated by the 1T single layer is therefore arguably the most consequential result of the study. When integrated into a full proton-exchange membrane water electrolyser, the catalyst sustained a current density of approximately 2.9 amperes per square centimeter at a cell voltage of 1.70 volts for more than 1,100 hours of continuous operation. Industrial electrolysers typically operate at current densities in the range of one to a few amperes per square centimeter, so the demonstration sits squarely in the regime that matters for real-world deployment.

Reaching that level of performance required first solving a synthesis problem that has long frustrated materials chemists. The 1T phase of RuO2 is metastable, meaning it is not the thermodynamically favored arrangement of ruthenium and oxygen atoms; left to its own devices, the material prefers to settle into the rutile structure. Metastable phases in two-dimensional materials, from the 1T polymorphs of molybdenum disulfide to exotic iridium oxide phases, often carry enhanced catalytic properties precisely because their unusual geometries reshape the electronic structure, but stabilizing them at scale is notoriously difficult. The Soochow-led team designed and fabricated a mechanothermal reactor, developed by co-author Mingwang Shao, to drive the formation of the single-layer 1T phase, and confirmed the resulting structure through a battery of characterization techniques including synchrotron-based X-ray absorption spectroscopy performed at facilities in Taiwan and Hefei.

The spectroscopic evidence was central to establishing why the edge-sharing geometry works. Using in situ ruthenium L3-edge X-ray absorption spectroscopy, together with total-electron-yield measurements at other absorption edges, the researchers probed the electronic and geometric state of the catalyst while it was actively evolving oxygen. Complementary density functional theory calculations, carried out by Zhiwei Hu, Jing Zhou, Chang-Yang Kuo and colleagues, rationalized the observations: the edge-sharing motif aligns the ruthenium 4d orbitals across adjacent octahedra, lowering the barriers for electron delocalization and stabilizing the reaction intermediates along the OER pathway. Attenuated-total-reflectance infrared measurements tracked the surface intermediates during operation, allowing the team to connect the macroscopic electrochemical performance to specific molecular events at the active sites.

The broader significance of the work lies in its reframing of catalyst design for acidic water oxidation. Much of the recent effort in the field has focused on compositional strategies: doping ruthenium oxide with rhenium, rhodium or tantalum, creating high-entropy oxides, or stabilizing iridium in perovskite-derived frameworks. Those approaches tune the electronic structure of essentially rutile-like lattices. The new study demonstrates that the connectivity of the octahedral network itself, an architectural variable rather than a compositional one, can be the decisive lever. By choosing a phase in which edge-sharing octahedra create parallel orbital alignment, the researchers achieved both the activity and the stability that compositional tuning has struggled to deliver simultaneously. This suggests a rich design space of metastable oxide phases, particularly in two-dimensional form, that the community has only begun to explore.

There are, of course, caveats and next steps. The 1T phase is metastable, and while the electrolyser test exceeded 1,100 hours, commercial PEM systems are expected to operate for tens of thousands of hours; long-term phase stability under thermal and potential cycling remains to be proven. Scaling the mechanothermal synthesis from laboratory batches to the kilogram quantities needed for stack manufacturing will require engineering development. And the precise balance between adsorbate-evolution and lattice-oxygen mechanisms on the 1T surface, a question the operando spectroscopy begins to answer, will continue to be refined as more theoretical and experimental data accumulate. Nevertheless, the combination of a 77-millivolt overpotential, a turnover frequency approaching 24 per second and sustained industrial-scale current density in a working electrolyser represents a level of integrated performance that few acidic OER catalysts have approached.

If the durability and manufacturability hurdles can be cleared, the implications for the hydrogen economy are substantial. PEM electrolysers are prized for their fast response and high output pressure, making them natural partners for intermittent renewable electricity, but their reliance on iridium, one of the scarcest elements on Earth, has been viewed as a hard ceiling on global deployment. A ruthenium-based anode catalyst that is both more active and more stable than rutile RuO2, and that has already demonstrated more than a thousand hours of operation at 2.9 amperes per square centimeter, offers a credible path toward easing that constraint. The edge-sharing single layer of ruthenium dioxide may thus be remembered less as a single catalyst and more as a proof of principle: that in the search for efficient acidic water splitting, the way atoms are wired together can matter as much as which atoms are chosen.

Subject of Research: Edge-sharing single-layer 1T-RuO2 electrocatalysts for acidic oxygen evolution in proton-exchange membrane water electrolysis

Article Title: Edge-sharing RuO2 single layer for stable and low overpotential acidic water electrolysis

Article References: Zhu, W., Zhou, J., Ma, M., Liu, H., Liao, F., Huang, H., Kuo, C.-Y., Lin, Y., Pao, C.-W., Chang, Y.-C., Haw, S.-C., Hsu, S.-Y., Chen, J.-M., Ni, M., Liu, Y., Shao, M., Hu, Z., Kang, Z., Huang, X., & Shao, Q. (2026). Edge-sharing RuO2 single layer for stable and low overpotential acidic water electrolysis. Nature Nanotechnology. https://doi.org/10.1038/s41565-026-02255-5

Image Credits: AI Generated

DOI: 10.1038/s41565-026-02255-5

Keywords: ruthenium dioxide, water electrolysis, oxygen evolution reaction, green hydrogen, proton-exchange membrane, electrocatalysis, two-dimensional materials, metastable phase, overpotential, PEM electrolyser, single-layer catalyst, acidic water oxidation