The team, led by Xiaoxue Liu, Yazhong Chen, Haifeng Wu, Xiaolin Sun, Bing Li, Xueping Wu, and Xianlong Zhang, prepared a family of catalysts labeled Mnx/SFCCC, where x denotes the weight percent of manganese loaded onto the support. The support, SFCCC, is spent fluid catalytic cracking catalyst, the used zeolite-based material that petroleum refineries discard by the ton once it loses activity in cracking units. Rather than letting this spent material go to landfill, the researchers repurposed it as a scaffold for manganese oxide, dramatically cutting the cost of the final catalyst while giving the waste a second life.

Because the way a catalyst is made can matter as much as what it is made of, the group synthesized their materials by three distinct routes: in situ deposition, precipitation-deposition, and incipient wetness impregnation. In situ deposition forms manganese oxide directly on the support surface under reaction conditions, precipitation-deposition builds the oxide through controlled precipitation onto the support, and incipient wetness impregnation soaks the support pores with a precursor solution before drying and calcination. Each technique distributes the manganese differently, and those differences in dispersion, particle size, and surface chemistry translate directly into differences in catalytic behavior.

To understand why one preparation outperformed the others, the researchers characterized their samples with an extensive toolkit. Low-temperature nitrogen adsorption measured surface area and pore structure, X-ray diffraction and scanning electron microscopy probed crystalline phase and morphology, hydrogen temperature-programmed reduction and oxygen temperature-programmed desorption assessed redox behavior and oxygen mobility, and X-ray photoelectron spectroscopy and electron paramagnetic resonance revealed surface oxidation states and defect sites. Inductively coupled plasma optical emission spectrometry confirmed the actual manganese loading in each batch. Together these measurements connected synthetic route, physical structure, and chemical functionality in a single coherent picture.

The performance results were striking. The catalyst prepared by in situ deposition with 14 weight percent manganese, Mn14/SFCCC-SP, delivered the best outcomes of the entire series. In static testing with an initial formaldehyde concentration of 4.5 parts per million, it removed 90.0 percent of the gas within 120 minutes at room temperature. Under dynamic conditions in a fixed-bed reactor, more representative of a real air purification device, it achieved greater than 95 percent removal at a gas hourly space velocity of 34,000 milliliters per gram per hour with an initial formaldehyde concentration of 7.0 parts per million. The catalyst also showed good stability and consistent performance across repeated use cycles, a critical requirement for any practical air-cleaning product.

The characterization data explain this superiority. Mn14/SFCCC-SP possesses a high specific surface area of 158 square meters per gram together with substantial pore volume, providing abundant sites where formaldehyde molecules can adsorb and react. The spent FCC support itself contributes porosity and a chemically heterogeneous surface, while the in situ deposition method deposits manganese oxide in a highly dispersed, well-contacted form rather than in bulky crystalline aggregates that bury active sites. High dispersion means more manganese atoms sit at the interface where gas molecules can reach them.

Even more important is the catalyst’s oxygen chemistry. X-ray photoelectron spectroscopy and electron paramagnetic resonance showed that the best sample carries a high concentration of surface-adsorbed oxygen species and oxygen vacancies, defects in the oxide lattice where an oxygen atom is missing. These vacancies are generated through the Mn4+/Mn3+ redox couple: when manganese cycles between its +4 and +3 oxidation states, lattice oxygen is consumed and replenished, continuously creating and refilling vacancy sites. The redox couple also gives the material good low-temperature reducibility, meaning it can activate oxygen molecules from air and transfer them to adsorbed formaldehyde even without external heating.

This mechanism sits at the heart of why the result matters. In the Mars-van Krevelen-type process that governs manganese oxide catalysts, formaldehyde first adsorbs on the surface, reacts with reactive oxygen to form intermediates such as formate and dioxymethylene species, and is finally oxidized to carbon dioxide and water, while gas-phase oxygen refills the vacancies the reaction consumed. A catalyst rich in vacancies and easily exchanged oxygen keeps this cycle running briskly at ambient temperature. The Hefei team’s evidence that the Mn4+/Mn3+ redox couple generates the vacancies that drive the reaction provides a clear design rule: maximize the interfacial contact between well-dispersed manganese oxide and a porous, defect-friendly support.

The choice of support is what makes the work economically compelling. Spent FCC catalysts are generated worldwide in enormous quantities, and disposal is an ongoing cost and environmental burden for refiners. Previous studies have explored supports ranging from activated carbon and diatomite to palygorskite, halloysite, and montmorillonite, often with excellent catalytic results but at a price that hinders scale-up. Using a pre-existing industrial waste stream as the support flips the cost equation: the raw material is essentially free, widely available, and already engineered to have favorable particle properties from its first life in the refinery. The authors specifically highlight that SFCCC was chosen to significantly reduce the cost of the catalyst, and the strong performance of the in situ deposition route shows that low cost need not come at the expense of activity.

For consumers, the implications are tangible. A room-temperature formaldehyde oxidation catalyst that maintains over 95 percent removal under demanding flow conditions could be integrated into air purifiers, ventilation systems, and building materials, continuously eliminating a carcinogenic pollutant rather than temporarily trapping it. Because the active component is abundant manganese rather than precious platinum, silver, or gold, the materials cost of deployment falls by orders of magnitude. And because the support is recycled refinery waste, the catalyst’s own footprint shrinks, turning one industrial waste problem into a solution for another environmental one. The study, published in Catalysis Letters, demonstrates that careful attention to preparation method, manganese loading, and support chemistry can transform a discarded powder into a high-performing environmental catalyst. As indoor air quality gains attention as a public health issue, such cheap, stable, and efficient room-temperature catalysts may soon move from the laboratory bench into the devices quietly cleaning the air in homes, offices, and schools.

Subject of Research: Room-temperature catalytic oxidation of formaldehyde using manganese oxides supported on spent FCC catalyst

Article Title: Room-Temperature Catalytic Oxidation of Formaldehyde Over Manganese Oxides Supported on SFCCC Prepared via Different Methods

Article References: Liu, X., Chen, Y., Wu, H., Sun, X., Li, B., Wu, X., & Zhang, X. (2026). Room-Temperature Catalytic Oxidation of Formaldehyde Over Manganese Oxides Supported on SFCCC Prepared via Different Methods. Catalysis Letters, 156(10), Article 279. https://doi.org/10.1007/s10562-026-05513-2

Image Credits: AI Generated

DOI: 10.1007/s10562-026-05513-2

Keywords: formaldehyde, manganese oxides, spent FCC catalyst, room temperature catalysis, oxygen vacancies, indoor air purification, catalyst preparation, redox couple, waste recycling, Catalysis Letters, Room-Temperature, Catalytic

The material at the heart of the work is a lithium manganese oxide cathode with the formula Li1.27Mn1.73O4, a composition typical of spent lithium-ion batteries from the lithium-manganese-oxide family. Instead of dismantling the chemistry and rebuilding the catalyst from purified metal salts — the conventional, energy-hungry approach — the team treated the spent cathode powder itself as the precursor. After removing the residual lithium using a deep eutectic solvent system based on choline chloride and lactic acid, they were left with a manganese-rich oxide framework ready to be activated. This lithium-extraction step proved critical, because the removal of lithium ions from the host lattice destabilizes the crystal structure and opens the door to defect formation on a scale that ordinary synthesis routes rarely achieve.

The second ingredient in the recipe is the heating method. Rather than ramping up a muffle furnace over hours, the researchers employed flash Joule heating, a technique in which a large electrical current is passed directly through the sample, generating intense heat within the material itself in seconds. The team systematically varied the applied current, producing a series of catalysts labeled FMn-aA, where the current ranged up to 25 amperes. For comparison, they also prepared catalysts from the same battery-derived material using conventional muffle-furnace calcination, and from analytical-grade metal salts processed both ways. This four-way comparison allowed them to isolate the individual and combined effects of the precursor source and the heating regime.

The results were striking. The optimized catalyst, designated FMn-25A, achieved more than 90 percent conversion of benzene at only 208 degrees Celsius. In the catalytic oxidation of VOCs, the temperature at which 90 percent of the pollutant is converted — known as T90 — is a key benchmark, because lower operating temperatures translate directly into lower energy costs and reduced risk of unwanted byproduct formation. Manganese oxides are well known catalysts for this chemistry, but reaching such low light-off temperatures typically requires careful doping, composite formation or noble metal promotion. Here, the researchers obtained the performance simply by choosing a waste-derived precursor and heating it in the right way.

The reason for the enhanced activity lies in the defect chemistry of the material. Detailed characterization combining X-ray diffraction, electron microscopy, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, oxygen temperature-programmed desorption and electron paramagnetic resonance showed that flash Joule heating combined with lithium-ion removal generated an unusually high density of oxygen vacancies — atomic-scale holes in the oxide lattice where an oxygen atom is missing. These vacancies are not passive imperfections. They are chemically active sites that change the electronic environment of neighboring manganese atoms, making the lattice easier to reduce and reoxidize, and they create anchoring points where gas-phase oxygen can adsorb and be converted into reactive oxygen species.

To trace exactly how benzene is destroyed on these surfaces, the team turned to in-situ diffuse reflectance infrared Fourier transform spectroscopy, or DRIFTS. This technique monitors the chemical species present on a catalyst surface while the actual reaction is running. The spectra revealed that the abundant oxygen vacancies promoted the formation of active oxygen species, which then attacked the benzene ring and its partially oxidized intermediates, accelerating the entire oxidation cascade toward complete conversion to carbon dioxide and water. In essence, the vacancies act as continuous suppliers of the reactive oxygen that drives the chemistry, explaining why the defect-rich battery-derived catalysts outperformed their conventionally prepared counterparts, including the CMn-MS sample made from metal salts in a muffle furnace and the salt-derived catalyst heated by flash Joule heating.

The study also underscores a broader lesson about how synthesis conditions shape catalytic materials. Conventional furnace calcination proceeds slowly and at relatively moderate temperatures, allowing the oxide lattice to relax into well-ordered, defect-poor configurations. Flash Joule heating, by contrast, delivers an extreme thermal shock followed by rapid cooling, freezing in a metastable, defect-rich structure. When applied to a lithium-depleted battery cathode — a lattice already destabilized by the extraction of lithium ions — this thermal shock produces exactly the kind of oxygen-deficient, highly reducible surface that low-temperature oxidation catalysis demands. The finding aligns with a growing body of literature on rapid Joule heating for catalyst preparation, which has shown that ultrafast thermal processing can create single-atom sites, defective graphenes and nanostructured electrocatalysts that are difficult or impossible to obtain through conventional routes.

The environmental logic of the approach is twofold. On the waste side, recycling strategies for spent lithium-ion batteries have so far concentrated on recovering lithium, cobalt and nickel from high-value ternary cathodes, while manganese-based cathodes have attracted less commercial attention and often end up in lower-value applications or landfill. Converting this material directly into environmental catalysts gives it a productive second life without demanding the purity levels required for new battery manufacturing. Earlier work by the same research group and others has already demonstrated that spent battery materials can serve as precursors for ammonia-selective catalytic reduction catalysts and for catalysts that simultaneously remove nitrogen oxides and VOCs. The present study extends that concept to lithium manganese oxide chemistry and, crucially, combines it with ultrafast electrified heating rather than energy-intensive furnace treatment.

On the pollution side, catalytic oxidation is one of the most effective technologies for destroying VOC emissions, but its industrial adoption has been constrained by the high temperatures — often above 300 degrees Celsius — that conventional catalysts require to achieve complete conversion. Every hundred degrees saved is a meaningful cut in operating energy and cost, particularly for dilute emission streams from painting, printing, petrochemical and smelting operations, sectors that are significant VOC sources and the focus of tightening regulation. A catalyst that reaches 90 percent benzene conversion at 208 degrees Celsius, made from waste rather than fresh chemicals and activated without prolonged furnace heating, addresses the economic and sustainability dimensions of the problem simultaneously. The authors describe the work as a sustainable strategy for green industrial VOC abatement, and the research was supported by China’s National Science and Technology Major Project on regional environmental improvement in the Beijing-Tianjin-Hebei area.

Significant steps remain before the concept reaches industrial deployment. Real emission streams contain water vapor, sulfur compounds and mixtures of VOCs that can poison or deactivate catalysts, and the long-term stability of a defect-rich structure under continuous operation must be demonstrated. Scaling flash Joule heating from laboratory powder samples to the throughput of a working air-cleaning unit is another engineering challenge, although the process is inherently fast and electrically driven, which favors energy efficiency and compatibility with renewable power. Nevertheless, the study offers a compelling proof of principle: the defective, highly reactive materials that catalyst designers usually struggle to engineer can emerge naturally — and almost instantly — from the wreckage of yesterday’s batteries. In turning one environmental liability into the cure for another, the work captures the kind of cross-cutting chemistry that may define the next generation of sustainable pollution control.

Subject of Research: Flash Joule heating fabrication of defect-rich manganese oxide catalysts from spent lithium-ion battery cathodes for low-temperature VOC oxidation

Article Title: Flash Joule Heating–Driven Fabrication of Defect-Rich Catalysts Derived from Spent Li1.27Mn1.73O4 Batteries for Low-Temperature VOCs Oxidation

Article References: Wang, X., Zheng, Y., Guo, H. Y., Duan, X. H., Gong, C., & Xue, G. (2026). Flash Joule Heating–Driven Fabrication of Defect-Rich Catalysts Derived from Spent Li1.27Mn1.73O4 Batteries for Low-Temperature VOCs Oxidation. Catalysis Letters, 156(10), Article 283. https://doi.org/10.1007/s10562-026-05527-w

Image Credits: AI Generated

DOI: 10.1007/s10562-026-05527-w

Keywords: flash Joule heating, oxygen vacancies, spent lithium-ion batteries, benzene catalytic oxidation, manganese oxides, volatile organic compounds, low-temperature catalysis, lithium-ion removal, deep eutectic solvents, DRIFTS, catalyst recycling, VOC abatement