Molybdenum Boosts Catalyst That Scrubs Two Pollutants at Once and Shrugs Off Poisoning

Industrial flue gas is a notoriously dirty cocktail, carrying nitrogen oxides that seed smog and acid rain alongside volatile organic compounds that threaten human health. Cleaning both streams at once has long been a dream of catalysis researchers, because a single catalyst that handles NOx and VOCs simultaneously could replace two separate treatment stages, slashing cost, space, and complexity inside power plants and factories. A new study published in the Journal of Materials Science by Yang-wen Wu, Qiang Lu, and colleagues at North China Electric Power University brings that dream closer to reality, and its central insight is as much about resilience as it is about raw activity: a catalyst for the real world must survive the poisons that industrial exhaust throws at it.

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