Ruthenium Catalysts Held in Place by Iron-Nitrogen Sites Push Ammonia Synthesis Toward Mild Conditions

Ammonia sits at the heart of the modern chemical economy. It is the feedstock for most of the world’s fertilizer, and increasingly it is being promoted as a carbon-free carrier of hydrogen, a molecule that can be stored and shipped far more easily than hydrogen gas itself. Yet the way humanity makes ammonia has barely changed in a century. The Haber-Bosch process, the industrial workhorse since the early twentieth century, relies on iron-based catalysts operating at punishing temperatures and enormous pressures, consuming vast amounts of energy and generating significant pollution. As nations pursue decarbonization targets, often described as dual carbon goals, the search for catalysts that can synthesize ammonia under far gentler conditions has become one of the most consequential challenges in catalysis research.

Ruthenium has long been recognized as the most active single metal for breaking the stubborn triple bond of molecular nitrogen. Catalysts built from ruthenium nanoparticles can, in principle, synthesize ammonia at temperatures and pressures well below those demanded by iron. But ruthenium carries a practical weakness: its nanoparticles are prone to sintering and agglomeration when exposed to elevated temperatures. As tiny particles migrate across a support surface and merge, the number of exposed active sites shrinks, and with it the catalytic performance and long-term stability of the material. Preventing that degradation has become the central design problem for anyone hoping to turn ruthenium’s laboratory promise into industrial reality.

A recent study published in the journal Ionics by Zhenni Tan of the Fuyang Institute of Technology, together with Xuanbei Peng of Fuzhou University and Lingling Li of Hebei University of Technology, reports a strategy that addresses this problem through carefully engineered metal-support interactions. The team constructed a composite catalyst in which ruthenium nanoparticles are anchored to a porous carbon support that is itself rich in iron-nitrogen-carbon sites, known as Fe-N-C sites. These sites, embedded within the carbon architecture, act as a kind of chemical scaffolding that binds the ruthenium particles firmly in place while simultaneously tuning their electronic properties for the task of nitrogen activation.

The synthesis route is as notable as the result. The researchers began with ZIF-67, a metal-organic framework built around cobalt ions, and combined it with the sodium salt of ethylenediaminetetraacetic acid, NaFe(III)EDTA, as an iron source. High-temperature carbonization of these precursors transformed the framework into a porous nitrogen-doped carbon matrix containing abundant Fe-N-C coordination sites, with cobalt and iron distributed through the structure. Ruthenium nanoparticles were then introduced by an impregnation-reduction method, which deposited them uniformly across the support. The resulting material, designated RuFe/Co@NC, combines three metals in a single architecture: ruthenium as the primary active phase, and iron and cobalt integrated into the nitrogen-doped carbon scaffold.

Characterization of the new catalyst relied on a battery of standard but powerful techniques. Scanning electron microscopy and transmission electron microscopy revealed the morphology of the porous support and the distribution of the ruthenium nanoparticles, confirming that the particles were anchored uniformly rather than clustering into large aggregates. X-ray diffraction provided information about the crystalline phases present, while Raman spectroscopy probed the structure of the carbon matrix. X-ray photoelectron spectroscopy, which is sensitive to the chemical states and electronic environments of surface atoms, delivered perhaps the most telling evidence: clear signatures of electronic synergy and alloying effects among ruthenium, iron, and cobalt. In other words, the three metals do not merely coexist; they interact electronically in ways that reshape the coordination environment of the active sites.

That electronic interplay matters because ammonia synthesis is a delicate balancing act. The rate-limiting step in most catalysts is the dissociation of molecular nitrogen, which requires the catalyst to donate electrons into the nitrogen molecule’s antibonding orbitals. A catalyst surface that is too electron-poor struggles to activate nitrogen; one that binds nitrogen-derived intermediates too strongly becomes poisoned by them. By tuning the electronic structure of ruthenium through interaction with the Fe-N-C sites and the cobalt-containing framework, the composite catalyst appears to strike a more favorable balance, optimizing the coordination environment of the active sites and thereby improving both activity and stability.

The performance figures reported in the study are striking. After optimizing the iron doping content, the researchers found that a support containing 1.0 weight percent iron delivered the best activity. Under conditions of 400 degrees Celsius and 1 megapascal of pressure, the RuFe/Co@NC catalyst achieved an ammonia synthesis rate of 8.962 millimoles of ammonia per gram of catalyst per hour. For context, those conditions are dramatically milder than the roughly 400 to 500 degrees Celsius and 15 to 25 megapascals typical of industrial Haber-Bosch reactors, and the pressure in particular is more than an order of magnitude lower than conventional operating conditions.

Equally important is the catalyst’s behavior across a range of pressures. A well-known failure mode of ruthenium catalysts is hydrogen poisoning, in which hydrogen species adsorb strongly onto the active sites and block nitrogen from reaching them, throttling the reaction. The study reports that the RuFe/Co@NC composite shows no hydrogen poisoning across the pressure range from 0.2 to 5 megapascals. That robustness is significant for any future practical deployment, because industrial reactors experience varying partial pressures of hydrogen and nitrogen, and a catalyst that loses activity as pressure changes would be difficult to integrate into real processes.

The broader context of this work is a flourishing global effort to reinvent ammonia synthesis. Recent literature includes tandem catalysts pairing ruthenium single atoms with nanoparticles, machine-learning-assisted tuning of ruthenium-nitrogen bonds, electride supports such as calcium aluminide and yttrium silicide that donate electrons to nitrogen, and inverse-structure iron catalysts. Each approach attacks a different link in the chain of nitrogen activation. The contribution of the present study is to show that the support itself, when engineered with abundant Fe-N-C sites derived from a metal-organic framework precursor, can serve double duty: stabilizing ruthenium against sintering while electronically modifying it for better activity. The use of NaFe(III)EDTA as an iron source also suggests a relatively accessible route to controlling the iron content, which the study identifies as a key optimization variable.

There remain, of course, substantial distances between a laboratory result and a green ammonia plant. The reported synthesis rate, while impressive at 1 megapascal, would need to be matched by long-term durability testing, scalability of the metal-organic-framework-derived support, and integration with renewable-powered hydrogen production. The authors note that the data supporting their findings are available on reasonable request, and the work was supported by the Natural Science Foundation of Anhui Provincial Institutions of Higher Education. Still, the study offers a compelling demonstration of a principle that is increasingly central to modern catalysis: that the interface between a metal nanoparticle and its support is not passive real estate but an active design element. By making that interface tunable, researchers can coax even a well-studied metal like ruthenium into performance regimes that bring mild-condition ammonia synthesis closer to practical reality, a step with real implications for fertilizer production and the emerging hydrogen economy alike.

Subject of Research: Ruthenium-based catalysts with tunable metal-support interactions for mild-condition ammonia synthesis

Article Title: Ru-based catalysts with tunable metal–support interactions for efficient ammonia synthesis under mild conditions

Article References: Tan, Z., Peng, X., & Li, L. (2026). Ru-based catalysts with tunable metal–support interactions for efficient ammonia synthesis under mild conditions. Ionics. https://doi.org/10.1007/s11581-026-07536-6

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07536-6

Keywords: ammonia synthesis, ruthenium catalyst, Fe-N-C sites, metal-support interaction, Haber-Bosch process, nitrogen activation, hydrogen storage, heterogeneous catalysis, nitrogen-doped carbon, ZIF-67, green chemistry, catalyst stability