A new catalyst design could help clean up one of the most stubborn sources of industrial air pollution: nitrogen oxides released from engines, boilers, power plants, and chemical facilities. Researchers led by Guo, Hu, Wu and colleagues report that introducing titanium into a cerium–manganese oxide catalyst creates a form of nanoscale strain that substantially improves low-temperature ammonia-selective catalytic reduction, or NH₃-SCR. The approach is also reported to strengthen the catalyst’s resistance to water vapor and sulfur dioxide, two substances that frequently cripple pollution-control systems in real exhaust streams. Published in Nature Communications, the study focuses on Ce₈MnOₓ, a mixed oxide already recognized for its ability to activate both oxygen and nitrogen-containing molecules. By adding titanium, the researchers aim to transform its atomic structure rather than simply increasing its surface area or loading it with additional active metals.
Nitrogen oxides, commonly grouped as NOₓ, are chemically reactive gases associated with smog, acid deposition, fine-particle formation, and respiratory disease. In many industrial systems, the most established method for removing them is NH₃-SCR. In this process, ammonia reacts with NOₓ over a solid catalyst, ideally converting the pollutants into harmless nitrogen and water. The chemistry is deceptively demanding. A catalyst must work rapidly at temperatures that may fluctuate widely, avoid producing unwanted ammonia emissions, and remain active in the presence of steam, sulfur compounds, dust, and other exhaust contaminants. Conventional catalysts can perform well in a narrow temperature window, but low-temperature operation remains a major challenge because reactants may not adsorb or activate efficiently. Sulfur dioxide can also occupy active sites or generate sulfate species, while water competes with reactants and changes the catalyst’s surface chemistry.
The new work addresses this problem through what the researchers describe as strain engineering. At the atomic scale, strain occurs when the regular arrangement of atoms in a crystal lattice is compressed, stretched, or distorted. Such distortions can alter the distances between neighboring atoms, shift electronic energy levels, and change how strongly molecules bind to the surface. In catalytic materials, these effects can determine whether oxygen is mobile, whether nitrogen oxides can be activated, and whether ammonia reacts along a productive pathway or becomes trapped in an inactive form. Titanium does not merely act as an additional chemical ingredient in the Ce₈MnOₓ structure. Its incorporation changes the local lattice environment, producing defects and distortions that reshape the behavior of cerium and manganese sites—the centers believed to be crucial for redox reactions during NOₓ removal.
Cerium and manganese are particularly valuable in oxidation–reduction catalysis because they can cycle between different electronic states. Cerium can shift between Ce⁴⁺ and Ce³⁺, helping create and replenish oxygen vacancies, while manganese can access several oxidation states and participate in the transfer of electrons needed to activate reactants. Oxygen vacancies are missing oxygen atoms in the lattice, and they often serve as chemically flexible sites where gas molecules can attach, dissociate, or exchange oxygen with the solid. The titanium-induced strain is understood to modify the concentration, distribution, or reactivity of these vacancies. This can improve the movement of lattice oxygen and facilitate the redox cycle required to convert NOₓ into nitrogen. Rather than relying on a single type of active site, the engineered catalyst appears to coordinate several functions: ammonia adsorption, NOₓ activation, oxygen transfer, and regeneration of the surface.
The importance of the material’s low-temperature activity extends beyond laboratory performance. Exhaust-control systems often encounter gases that are too cool for conventional catalysts to operate efficiently, particularly during engine start-up, intermittent industrial operation, and periods of reduced load. Delayed catalyst activation allows NOₓ to escape precisely when emissions can be difficult to control. A catalyst that can drive NH₃-SCR at lower temperatures could reduce this gap and make pollution-control equipment more effective across a broader operating range. The study’s emphasis on Ce₈MnOₓ is also significant because cerium and manganese are generally more accessible and less costly than precious metals. Although practical deployment still depends on durability, manufacturing, reactor design, and full-scale testing, the work points toward a strategy based on controlling atomic structure instead of adding expensive components.
Real exhaust, however, contains far more than nitrogen oxides and ammonia. Water vapor is almost unavoidable, and its effect can be especially damaging at low temperatures. Water molecules may cover the catalyst surface, block adsorption sites, alter surface acidity, or stabilize inactive intermediates. Sulfur dioxide presents an even more persistent threat. It can react with catalytic surfaces to form sulfites or sulfates, species that may strongly bind to active sites and interfere with the redox cycle. In some systems, sulfur compounds also react with ammonia to produce ammonium sulfate or related deposits that obstruct pores and accelerate deactivation. The reported improvement in H₂O and SO₂ resistance therefore matters as much as the initial increase in NOₓ conversion. A catalyst that performs brilliantly in dry, sulfur-free gas but rapidly fails in realistic exhaust offers little practical advantage.
According to the study, titanium-induced strain helps the Ce₈MnOₓ catalyst preserve its active structure under these hostile conditions. The distorted lattice can influence how water and sulfur-containing species interact with the surface, while the modified electronic environment may prevent them from permanently poisoning the most important reaction sites. Improved oxygen mobility may also help the catalyst recover from temporary inhibition by restoring the oxidation states and vacancies needed for SCR chemistry. This does not mean sulfur and water become chemically irrelevant; rather, the material is designed to tolerate their presence without losing its ability to cycle between active states. Such resistance is a central requirement for long-lived emissions-control systems, where regeneration or replacement can be costly and operationally complicated.
The researchers’ findings also contribute to a broader shift in catalyst development. For decades, scientists often optimized catalysts by changing composition, particle size, porosity, or the amount of active metal. Those variables remain important, but strain engineering offers another level of control: manipulating the internal forces and distortions that govern surface chemistry. The same elemental composition can behave differently depending on how its atoms are arranged and how defects are distributed. Titanium doping demonstrates how a relatively small structural modification can influence several properties at once, including redox capacity, oxygen-vacancy behavior, adsorption strength, and resistance to poisons. The concept could potentially be extended to other mixed oxides and to catalytic reactions involving volatile organic compounds, methane, carbon monoxide, or electrochemical energy conversion, although each application would require its own mechanistic validation.
The study arrives as governments and industries face growing pressure to reduce air pollution without sacrificing reliable energy and transportation. Nitrogen-oxide regulations are becoming stricter, while many facilities must operate under changing temperatures, fuel compositions, and emissions loads. A low-temperature NH₃-SCR catalyst that combines high activity with water and sulfur tolerance could help bridge the gap between controlled laboratory chemistry and the unpredictable conditions of the field. The work does not by itself establish that the material is ready for commercial installation, and long-term tests involving thermal cycling, dust, hydrocarbons, ammonia slip, and complex fuel contaminants will be essential. Even so, the central message is powerful: by deliberately straining a catalyst’s atomic lattice, researchers may be able to make pollution-control chemistry faster, tougher, and more resilient. In the race to clean industrial air, the decisive breakthrough may come not from adding more material, but from persuading the atoms already present to work differently.
Subject of Research: Titanium-induced strain engineering of Ce₈MnOₓ catalysts for low-temperature ammonia-selective catalytic reduction of nitrogen oxides and improved resistance to H₂O and SO₂.
Article Title: Ti doping-induced strain engineering boosts low-temperature NH₃-SCR deNOₓ performance and H₂O/SO₂ resistance of Ce₈MnOₓ
Article References: Guo, X., Hu, Y., Wu, X. et al. “Ti doping-induced strain engineering boosts low-temperature NH₃-SCR deNOₓ performance and H₂O/SO₂ resistance of Ce₈MnOₓ.” Nature Communications (2026). https://doi.org/10.1038/s41467-026-76719-6
Image Credits: AI Generated
DOI: 10.1038/s41467-026-76719-6
Keywords: NH₃-SCR, deNOₓ, titanium doping, strain engineering, Ce₈MnOₓ, cerium–manganese oxide, nitrogen oxides, low-temperature catalysis, H₂O resistance, SO₂ resistance, oxygen vacancies, environmental catalysis
