The team’s starting material was a catalyst the group and others had already explored for synergistic pollutant removal: iron vanadate, FeVO4, dispersed on a titanium dioxide support. This combination is attractive because the vanadium and iron centers can drive both the selective catalytic reduction of NOx with ammonia and the oxidation of VOCs such as toluene, the two reactions that define simultaneous abatement. In laboratory settings, FeVO4/TiO2 performs admirably. But industrial environments are unforgiving. Alkali metals like potassium, released from coal and biomass combustion, and heavy metals like lead, volatilized in sintering plants and waste incinerators, drift onto catalyst surfaces and gradually strangle their activity. A catalyst that works beautifully on a clean feed but dies within months on a real flue gas is of limited practical value.

To quantify that threat, the researchers deliberately exposed their catalysts to potassium and lead species and measured how NO conversion and toluene oxidation responded. The results painted a nuanced picture. Potassium proved to be the more insidious enemy: it aggregated on the catalyst surface, blocking the acidic sites where ammonia must adsorb before it can reduce NOx, and directly poisoning the active sites responsible for the reaction. Lead, by contrast, turned out to be a surprisingly gentle adversary for this particular system. The unmodified FeVO4/TiO2 catalyst showed an intrinsic tolerance to lead, suffering only minor inhibition of NO conversion while actually exhibiting enhanced toluene oxidation, an intriguing case where the poison partially acted as a promoter rather than a killer.

The most sobering finding, however, came when both poisons were present at once. Simultaneous potassium and lead exposure caused far more severe deactivation than either element alone, revealing a synergistic poisoning effect in which the two contaminants compound each other’s damage. This observation matters because real flue gas never delivers its toxins one at a time. Any catalyst destined for industrial service must be evaluated against mixed-poison scenarios, and the study’s demonstration that combined K and Pb exposure is worse than the sum of its parts offers a warning to the field: single-poison laboratory tests may dramatically underestimate the degradation a catalyst will experience in the field.

The researchers’ countermeasure was molybdenum. By doping Mo into the FeVO4/TiO2 framework, they fundamentally changed how the catalyst responds to potassium attack. Spectroscopic and performance analyses showed that Mo modification alleviated the K-induced blockage of acid sites and the poisoning of active sites by suppressing the aggregation of potassium across the catalyst surface. Instead of potassium clustering into deactivating islands, it was held in a more dispersed, less damaging state. This anti-poisoning mechanism builds on a growing body of evidence that molybdenum addition can harden vanadia-based selective catalytic reduction catalysts against alkali metals, and the new work extends that strategy to the dual-function NOx-plus-VOCs setting.

Molybdenum did more than play defense. The doped catalyst also gained offensive advantages that boosted its baseline performance. Mo addition stabilized the high-valence V5+ and Fe3+ species, the redox workhorses that shuttle electrons during both the ammonia-SCR reaction and the oxidation of toluene, and it preserved an abundance of oxygen vacancies on the surface. Oxygen vacancies are critical in oxidation catalysis because they activate molecular oxygen and facilitate the Mars-van-Krevelen cycle through which lattice oxygen participates in breaking carbon-hydrogen bonds in VOC molecules. By keeping more of the vanadium and iron in their catalytically potent oxidation states and maintaining a vacancy-rich surface, the Mo-doped catalyst sustained the redox chemistry that underpins both pollutant-removal reactions.

The structural benefits extended to the pore network as well. Molybdenum incorporation improved the catalyst’s pore structure, providing more acid sites overall and promoting a more uniform and stable distribution of those sites across the surface. In an ammonia-SCR catalyst, acid sites are where the NH3 reagent adsorbs and is activated before reacting with NOx, so their quantity and accessibility directly govern NO conversion. A more even distribution means that incoming poisons cannot wipe out entire neighborhoods of activity in one strike, and a larger population of sites provides redundancy. Together with the stabilized redox species and the suppressed potassium migration, these effects explain why the Mo-doped catalyst retained its dual-function performance under poisoning conditions that crippled the undoped material.

The broader significance of the work lies in its design philosophy. Rather than chasing record activity numbers on clean feeds, the researchers treated poisoning resistance as a first-order design criterion, systematically evaluating deactivation mechanisms and engineering the catalyst to counter them. Their conclusions offer a theoretical foundation and a practical strategy for developing simultaneous NOx and VOCs removal catalysts with enhanced resistance to K and Pb poisoning. The approach, stabilizing high-valence active species, preserving oxygen vacancies, enriching and homogenizing acid sites, and physically frustrating the aggregation of alkali poisons, is modular and could plausibly be transferred to other catalyst families, including the ceria- and manganese-based systems that many groups are developing for low-temperature applications.

There remain hurdles between laboratory demonstration and industrial deployment. The durability of any catalyst must ultimately be proven over thousands of hours in genuine flue gas, where sulfur dioxide, water vapor, particulate matter, and temperature excursions add further stresses beyond the potassium and lead examined here. Regeneration protocols, mechanical strength, and manufacturing cost will also shape whether Mo-doped FeVO4/TiO2 ever lines the ducts of a working power plant. Yet the study delivers something the field genuinely needs: a mechanistically grounded account of how two common industrial poisons interact with a dual-function catalyst, and a demonstrated doping strategy that blunts their combined assault. As regulators tighten limits on both NOx and VOC emissions, and as industries from steel sintering to waste incineration seek compact end-of-pipe solutions, catalysts that can fight two pollutants at once and keep fighting through the poison will be in growing demand. This work shows that a single well-chosen dopant can tip the balance.

Subject of Research: Mo-doped FeVO4/TiO2 catalysts for simultaneous NOx and VOCs removal with enhanced resistance to potassium and lead poisoning

Article Title: Mo-doped FeVO4/TiO2 catalysts with abundant acidic sites for simultaneous NOx and VOCs abatement: enhanced resistance to K and Pb poisoning

Article References: Wu, Y.-W., Su, X., Li, X.-H., Xu, S., Wu, Z.-L., Zhou, X.-Y., Li, J.-H., & Lu, Q. (2026). Mo-doped FeVO4/TiO2 catalysts with abundant acidic sites for simultaneous NOx and VOCs abatement: enhanced resistance to K and Pb poisoning. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13896-1

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13896-1

Keywords: catalysis, NOx removal, VOCs oxidation, NH3-SCR, molybdenum doping, FeVO4/TiO2, potassium poisoning, lead poisoning, flue gas treatment, oxygen vacancies, acid sites, air pollution control

The research group, led by Lirui Sun and Zhaoyang Chen of the National Synchrotron Radiation Laboratory at the University of Science and Technology of China, together with Lidong Zhang and colleagues, prepared four catalysts under an identical protocol: pristine cerium dioxide, and the same oxide modified with iron, cobalt or nickel. Ceria is a fascinating material in its own right. Its fluorite crystal lattice can easily shed and reabsorb oxygen atoms, cycling between Ce4+ and Ce3+ oxidation states, which makes it a natural oxygen reservoir. In ammonia-SCR, that mobility is a double-edged sword. Lattice oxygen is needed to activate ammonia and nitric oxide, but if the oxygen is too aggressive it oxidises ammonia all the way to nitrogen dioxide or even nitrous oxide, destroying the selectivity that the reaction depends on.

The baseline results were sobering. Untreated cerium dioxide managed a peak nitrogen oxide conversion of just 14.83 percent at 300 degrees Celsius under a realistic oxygen-rich feed containing 0.5 percent NO, 0.5 percent NH3 and 5 percent O2. Worse, when the temperature rose to 350 degrees Celsius, conversion collapsed to 6.12 percent while the yield of nitrogen dioxide climbed to 24.92 percent. In other words, the bare catalyst was not merely inefficient — it was actively converting the desired reaction into over-oxidation, producing the very species that fast SCR chemistry needs only in carefully balanced amounts. Too much NO2 alongside insufficient NO conversion means the ammonia is wasted on side reactions rather than being stitched onto nitrogen oxide to form harmless nitrogen and water.

Adding iron changed the picture dramatically. The iron-modified ceria, dubbed FeCe, reached 79.8 percent nitrogen oxide conversion at 300 degrees Celsius and still delivered 75.7 percent at 350 degrees Celsius, while keeping nitrogen dioxide yield down to just 8.0 percent. That combination is the holy grail of this field: high activity and high over-oxidation resistance at the same time. Most catalysts trade one against the other — push the conversion up and the unwanted oxidation products follow. The FeCe sample broke that trade-off, sustaining strong performance across the temperature window where industrial flue gases typically sit.

The other two dopants told a more cautionary tale. Nickel modification shifted the activity maximum down to 250 degrees Celsius, where conversion peaked at 54.0 percent, but the catalyst fell off a cliff at higher temperatures, dropping to a mere 0.3 percent conversion at 350 degrees Celsius. Cobalt modification produced only a narrow low-temperature operating window before failing. Perhaps most striking was what the conventional characterisation techniques revealed. By the usual proxies — X-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy — the nickel-modified sample displayed the strongest defect signatures of all three doped materials. By every standard metric of oxygen vacancy abundance, NiCe should have been the star of the show. Instead, it underperformed the iron catalyst above 250 degrees Celsius by a wide margin.

That paradox is the intellectual heart of the study, and the authors resolved it by looking more carefully at dopant speciation — the chemical form each metal actually adopts inside the ceria host. The three transition metals, despite sitting side by side in the periodic table, chose three entirely different fates. Iron dissolved into the ceria lattice, substituting for cerium atoms and generating oxygen vacancies deep in the bulk crystal. Nickel refused to incorporate and instead precipitated as discrete nickel oxide particles, concentrating vacancies at the NiO/CeO2 interface. Cobalt phase-separated into cobalt oxide, a strongly oxidising spinel phase with its own aggressive oxygen chemistry. Three metals, three architectures, three completely different ways of supplying and positioning reactive oxygen.

Density functional theory calculations then explained why location matters more than quantity. The lattice-substituted iron site combined the lowest oxygen vacancy formation energy among the tested configurations with the widest calculated free-energy separation between two competing reaction channels: the selective pathway in which activated ammonia couples with nitric oxide to form nitrogen, and the non-selective pathway in which lattice oxygen strips hydrogen from ammonia, driving over-oxidation. When the vacancy sits in the bulk lattice near an iron centre, the energetic landscape favours N–N coupling and penalises dehydrogenation. When vacancies cluster at an external interface, as in the nickel case, the local oxygen supply becomes too reactive, tipping the balance toward ammonia destruction at elevated temperatures — which is exactly why NiCe, despite its abundant defect signatures, fell apart above 250 degrees Celsius.

The implications reach well beyond this particular reaction. Oxygen vacancies have become the darling of defect engineering across catalysis, energy storage and electronics, and the field has largely operated on the assumption that more vacancies mean better performance. This study delivers a sharp corrective: vacancy concentration is a crude proxy, and vacancy location is the variable that actually governs the activity–selectivity balance. A catalyst bristling with interface vacancies can look superb under spectroscopic scrutiny and still fail in a reactor, while a lattice-doped material with fewer but better-placed defects can dominate. For ceria-based systems, the message is that dopants must be chosen not just for their electronic properties but for their willingness to enter the lattice rather than segregate out of it.

There is also a practical dimension. Vanadium-based SCR catalysts, typically vanadium pentoxide on titania with tungsten or molybdenum promoters, operate effectively only above roughly 300 degrees Celsius and suffer from vanadium toxicity and ammonia slip issues. A ceria–iron system that sustains nearly 80 percent conversion at 300 degrees Celsius with strong resistance to over-oxidation points toward vanadium-free formulations that could work closer to the source of emissions, where flue gases are cooler, reducing reheating costs. The work was supported by the National Natural Science Foundation of China and the Natural Science Foundation of Anhui Province, and the authors included collaborators from the China Automotive Technology and Research Center, suggesting an eye toward mobile-source applications where low-temperature operation is especially valuable.

What makes this study resonate is its methodological discipline. By preparing all four catalysts under one identical protocol and evaluating them under one identical feed, the team eliminated the confounding variables that plague much of the comparative catalysis literature. The combination of structural characterisation, careful activity testing and first-principles energetics produced a self-consistent story in which every observation — the collapse of bare ceria, the triumph of iron, the paradox of nickel, the narrow window of cobalt — follows from a single principle. Oxygen vacancies are not interchangeable widgets to be counted; they are positional players whose placement in the crystal determines whether they supply oxygen gently enough to build nitrogen bonds or aggressively enough to burn the reductant. As researchers pursue next-generation environmental catalysts, that distinction may prove to be the difference between a promising material and a deployable one.

Subject of Research: Dopant speciation and oxygen-vacancy location in Fe-, Co- and Ni-modified CeO2 catalysts for low-temperature NH3-SCR of nitrogen oxides

Article Title: Unraveling the Role of Dopant Speciation in Oxygen-Vacancy Location and Lattice-Oxygen Supply over Fe-, Co- and Ni-Modified CeO2 NH3-SCR Catalysts

Article References: Sun, L., Chen, Z., Xu, W., Zhang, L., & Li, Z. (2026). Unraveling the Role of Dopant Speciation in Oxygen-Vacancy Location and Lattice-Oxygen Supply over Fe-, Co- and Ni-Modified CeO2 NH3-SCR Catalysts. Catalysis Letters, 156(10), Article 288. https://doi.org/10.1007/s10562-026-05532-z

Image Credits: AI Generated

DOI: 10.1007/s10562-026-05532-z

Keywords: NH3-SCR, ceria, oxygen vacancies, dopant speciation, lattice oxygen, iron doping, nickel oxide, cobalt oxide, DFT calculations, nitrogen oxides, over-oxidation resistance, vanadium-free catalysts

The conventional way of making manganese-cerium mixed oxides starts with soluble metal salts, typically nitrates, which are combined through coprecipitation or impregnation. Those routes carry real drawbacks: the procedures are multi-step and difficult to control, the salt solutions generate their own pollutant streams, and the active metal loading on the final support tends to be low. The research team, led by Min Kang and Jian Yu with collaborators at several Chinese institutions, sidestepped the problem by starting from manganese carbonate and cerium carbonate, cheap and stable crystalline solids that are already produced at industrial scale. The trick was finding a way to persuade two stubbornly insoluble carbonates to mix intimately at the molecular level, and the answer turned out to be a humble kitchen-adjacent chemical: oxalic acid.

When the powdered carbonate precursors are treated with oxalic acid, a remarkable transformation occurs. The crystalline carbonates dissolve and reprecipitate as viscous, amorphous oxalate species in which manganese and cerium are chemically intermingled rather than merely sitting side by side as separate grains. This chemical mixing, which the authors distinguish from simple physical blending, is the heart of the method. Structural characterization by X-ray diffraction showed that the oxalate intermediates lose their long-range order, while thermogravimetric analysis revealed a second crucial benefit: the homogeneous oxalate precursors decompose at a lower temperature, between 250 and 300 degrees Celsius, compared with physically mixed carbonates. During that decomposition they also release more carbon dioxide gas, and it is this escaping gas that does the sculpting.

As the oxalate precursor breaks down and CO2 streams out of the shrinking solid, it leaves behind a porous manganese-cerium oxide framework riddled with voids. Measurements of surface area and pore volume using the Brunauer-Emmett-Teller method confirmed that the chemically mixed catalyst possesses a significantly larger specific surface area and pore volume than material made by physically mixing the same carbonates. The morphology that emerges is strip-shaped, a form the authors highlight as suitable for industrial catalyst bodies, which are often shaped into pellets, plates, or honeycombs that must withstand gas flow without excessive pressure drop. Large pores matter in real flue gas service because they allow molecules to diffuse quickly to active sites and are less prone to clogging by dust and aerosols.

Why does intimate mixing of manganese and cerium matter so much for the catalysis itself? The answer lies in the electronic handshake between the two oxides. When manganese oxide domains and cerium oxide domains are finely interspersed, the interface generates abundant defect sites, including oxygen vacancies where an oxygen atom is missing from the crystal lattice. These vacancies, together with highly mobile surface active oxygen species, form the reactive heart of the catalyst. X-ray photoelectron spectroscopy indicated a higher proportion of surface active oxygen in the chemically mixed sample, and the manganese and cerium atoms engage in a facile redox cycle, shuttling electrons back and forth as the reaction proceeds. Ammonia temperature-programmed desorption experiments showed an increased density of acid sites, which anchor the ammonia reductant molecules needed for the selective catalytic reduction reaction.

In the selective catalytic reduction process, ammonia is injected into the flue gas and reacts with nitric oxide over the catalyst surface to produce harmless nitrogen and water. The performance figures reported for the carbonate-derived MnCeOx catalyst are striking. At 150 degrees Celsius, a temperature at which many commercial vanadia-based catalysts are essentially dormant, the material achieved close to 100 percent denitrification efficiency. More important for any real installation, the catalyst held its activity over a 168-hour continuous test, maintaining conversion above 94 percent even under demanding conditions: 30 volume percent water vapor, a level typical of wet flue gases, and a sulfur dioxide concentration of 50 milligrams per normal cubic meter. Sulfur and water resistance has historically been the Achilles heel of manganese-based low-temperature catalysts, because sulfur dioxide reacts with surface sites to form stable sulfates and water competes with ammonia for adsorption.

The authors attribute the exceptional sulfur tolerance to the same structural features that drive the high activity. The large pore volume gives sulfur species less opportunity to block the network of channels, and the sheer abundance of exposed active sites means that even if some are deactivated by sulfate formation, plenty remain available to keep the reaction going. The strong Mn-Ce interaction also appears to moderate the severity of sulfation on the manganese sites themselves, a phenomenon that previous studies of Mn-Ce systems have linked to cerium’s oxygen storage and release capacity. Cerium oxide is famous as an oxygen buffer, absorbing and releasing oxygen as conditions fluctuate, and that buffering stabilizes the redox state of neighboring manganese atoms under the reducing and oxidizing swings of a working flue gas stream.

The comparative experiments in the study sharpen the message about preparation chemistry. Samples made by physically mixing the two carbonates and calcining them at either 300 or 400 degrees Celsius performed markedly worse than the chemically mixed counterparts calcined at the same temperatures. The difference traces back to the precursor stage: physical mixing leaves manganese and cerium in separate crystalline carbonate grains, so even after decomposition the two oxides remain poorly interleaved, with fewer interface sites, fewer defects, and less active oxygen. The oxalic acid route effectively performs the mixing at the molecular scale before any heat is applied, which is why the resulting oxide inherits such a favorable architecture. Calcination temperature mattered as well, with the 300-degree samples retaining the fine dispersion that higher temperatures begin to erode through sintering.

There is also a green-chemistry dimension to the work that extends beyond the catalyst’s performance. By replacing soluble metal salts with carbonates, the synthesis avoids nitrate-containing waste streams and the corrosive, fuming solutions that industrial plants must handle and treat. Oxalic acid is inexpensive, widely available, and acts here as a chemical molding additive that shapes the precursor into workable strips. The lower decomposition temperature of the oxalate route, 250 to 300 degrees Celsius rather than the higher temperatures often needed to fully break down carbonates, translates directly into lower energy consumption during the calcination step, which for a catalyst produced in tonnage quantities is a meaningful cost and emissions saving. The released carbon dioxide is the only major gaseous byproduct of the precursor transformation.

The broader context makes the advance timely. Low-temperature denitrification is increasingly demanded by industries such as coking, cement, glass, and steel, where exhaust gases leave stacks at temperatures far below the window in which conventional catalysts operate, and where reheating the gas is economically prohibitive. Manganese-based catalysts have long been recognized as the most promising family for sub-200-degree operation, but translating laboratory powders into durable industrial bodies has remained the bottleneck. By demonstrating a route that starts from cheap carbonates, uses a simple acid treatment, yields a strip-shaped body suited to industrial forming, and delivers near-complete NOx conversion with robust resistance to water and sulfur, the researchers have addressed several of those bottlenecks at once. If the approach scales as its chemistry suggests it should, the humble carbonate, long treated as a dull industrial commodity, may find a new starring role in cleaning the air above the world’s heaviest industries.

Subject of Research: Carbonate-derived MnCeOx catalysts for low-temperature selective catalytic reduction of NOx in flue gas

Article Title: The Fabrication of Strip-Shaped Industrial MnCeOx Catalyst Derived from Carbonates for Flue Gas Denitrification

Article References: Kang, M., Xu, M., Xiao, P., Xiao, Y., Li, C., Fu, W., Xu, Y., Yu, Z., & Yu, J. (2026). The Fabrication of Strip-Shaped Industrial MnCeOx Catalyst Derived from Carbonates for Flue Gas Denitrification. Catalysis Letters, 156(9), Article 268. https://doi.org/10.1007/s10562-026-05520-3

Image Credits: AI Generated

DOI: 10.1007/s10562-026-05520-3

Keywords: MnCeOx catalyst, flue gas denitrification, NH3-SCR, carbonate precursors, oxalic acid, low-temperature catalysis, nitrogen oxides, sulfur resistance, oxygen vacancies, industrial catalysts, manganese oxide, cerium oxide