Electrospinning Equipment: Electrospinning M/TiO₂ Nanofibers for VOC Removal via Photothermal Catalysis

Volatile Organic Compounds (VOCs) are organic compounds that, as atmospheric pollutants, contribute to the greenhouse effect and pose risks to human health. Among the technologies for reducing VOCs, catalytic oxidation technology has garnered broad attention due to its ability to convert VOCs into harmless products such as CO₂ and H₂O. However, traditional catalytic oxidation requires high reaction temperatures to completely destroy VOCs. Although photocatalytic oxidation can oxidize low concentrations of VOCs at low temperatures, it suffers from low removal efficiency and catalyst deactivation. The synergistic effect of thermal catalysis and photocatalysis can maximize catalytic activity at lower temperatures, making photothermal catalysis a promising technology for VOC treatment.

A team led by Dr. Ye Qing from the College of Environmental Science and Engineering at Beijing University of Technology has published their latest research findings on the "Photothermal synergistic effect of M/TiO₂ nanofiber catalysts prepared by electrospinning in removing VOCs" in the journal Journal of Environmental Chemical Engineering. The team successfully prepared a series of M/TiO₂ (M = Cu, Mn, Co, Ni) nanofiber catalysts via electrospinning and elucidated the photothermal synergistic mechanism in toluene oxidation. This achievement offers a new technological approach for the efficient low-temperature treatment of VOCs and lays a theoretical foundation for the development of novel and highly efficient catalysts.

The team prepared a series of M/TiO₂ (M = Cu, Mn, Co, Ni) nanofiber catalysts using the electrospinning technique. They first mixed tetrabutyl titanate (TBT), ethanol, acetic acid, and polyvinylpyrrolidone (PVP) to form a uniform and transparent spinning precursor solution. For catalysts doped with different metals, the corresponding metal acetates (such as Cu(CH₃COO)₂, Mn(CH₃COO)₂, Co(CH₃COO)₂, and Ni(CH₃COO)₂) were added to the solution, which was then stirred until completely dissolved. The solution was subsequently spun into fibers using an electrospinning device. During the spinning process, the voltage was controlled at 15–18 kV, and the solution feeding rate was maintained at 2.0–2.5 mL/h. The fibers were calcined in air at a heating rate of 2℃/min to 500℃ and held for 1 hour to obtain the final M/TiO₂ nanofiber catalysts. This preparation method achieved uniform doping of metal ions, and the resulting nanofibers exhibited good dispersibility and high specific surface area, significantly enhancing the catalyst's activity and stability.

The catalytic performance of the different metal-doped TiO₂ catalysts in toluene oxidation was tested through thermal and photothermal catalytic experiments. The results showed that the Cu/TiO₂ catalyst exhibited the highest catalytic activity under both thermal and photothermal catalytic conditions, followed by Mn/TiO₂, TiO₂, Co/TiO₂, and Ni/TiO₂. Specifically, the temperatures required for the Cu/TiO₂ catalyst to achieve 10%, 50%, and 90% toluene conversion under photothermal catalytic conditions were 188℃, 229℃, and 267℃, respectively, which were significantly lower than those of the other catalysts.

The H₂-TPR experiment revealed that the Cu/TiO₂ catalyst had the lowest reduction peak temperature (241℃), indicating good low-temperature reducibility. This allows the Cu/TiO₂ catalyst to more easily activate reactants at low temperatures, thereby enhancing catalytic activity (Figure 4G). The CO-TPR results showed that the Cu/TiO₂ catalyst had the lowest lattice oxygen mobility temperature (100℃), indicating high lattice oxygen mobility. The high mobility of lattice oxygen helps to quickly replenish oxygen vacancies during the reaction, thereby maintaining the catalyst's high activity (Figure 4H).

In-situ DRIFTS revealed the reaction pathway of photothermal catalytic oxidation of toluene on Cu/TiO₂: Toluene and O₂ first react with photogenerated holes and electrons to form benzyl radicals and superoxide radicals (•O₂⁻). These benzyl radicals and superoxide radicals then combine with protons to form hydroperoxide intermediates. The hydroperoxide intermediates dehydrate to form benzaldehyde, which is further oxidized by O⁻ ions to yield benzoic acid. Finally, benzoic acid is completely oxidized to CO₂ and H₂O. In this process, adsorbed oxygen promotes the formation of benzaldehyde, while lattice oxygen mainly promotes the further decomposition of benzaldehyde.

Source of article: https://doi.org/10.1016/j.jece.2025.116261