Binder-Free Immobilization of Photocatalyst on Membrane Surface for Efficient Photocatalytic H2O2 Production and Water Decontamination

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Binder-Free Immobilization of Photocatalyst on Membrane Surface for Efficient Photocatalytic H2O2 Production and Water Decontamination
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Binder-Free Immobilization of Photocatalyst on Membrane Surface for Efficient Photocatalytic H2O2 Production and Water Decontamination - Nano-Micro Letters

In photocatalytic water treatment processes, the particulate photocatalysts are typically immobilized on membrane, through either chemical/physical loading onto the surface or directly embedding in the membrane matrix. However, these immobilization strategies inevitably compromise the interfacial mass diffusion and cause activity decline relative to the suspended catalyst. Here, we propose a binder-free surface immobilization strategy for fabrication of high-activity photocatalytic membrane. Through a simple dimethylformamide (DMF) treatment, the nanofibers of polyvinylidene fluoride membrane were softened and stretched, creating enlarged micropores to efficiently capture the photocatalyst. Subsequently, the nanofibers underwent shrinking during DMF evaporation, thus firmly strapping the photocatalyst microparticles on the membrane surface. This surface self-bounded photocatalytic membrane, with firmly bounded yet highly exposed photocatalyst, exhibited 4.2-fold higher efficiency in hydrogen peroxide (H2O2) photosynthesis than the matrix-embedded control, due to improved O2 accessibility and H2O2 diffusion. It even outperformed the suspension photocatalytic system attributed to alleviated H2O2 decomposition at the hydrophobic surface. When adopted for UV-based water treatment, the photocatalytic system exhibited tenfold faster micropollutants photodegradation than the catalyst-free control and demonstrated superior robustness for treating contaminated tap water, lake water and secondary wastewater effluent. This immobilization strategy can also be extended to the fabrication of other photocatalytic membranes with diverse catalyst types and membrane substrate. Overall, our work opens a facile avenue for fabrication of high-performance photocatalytic membranes, which may benefit advanced oxidation water purification application and beyond.

A multi-institute team led by Professors Tian Liu, Alicia Kyoungjin An and Wen-Wei Li has unveiled a binder-free “surface self-bounded photocatalytic membrane” (SSPM) that simultaneously produces green H2O2 and annihilates antibiotics in water. Published in Nano-Micro Letters, the work converts a simple PVDF nanofiber sheet into a high-activity reactor—no glue, no embedding, no energy-intensive steps.

Why Binder-Free Wins

  • Instant Catalyst Fixation: A 2-minute dimethylformamide (DMF) bath softens PVDF fibers, allowing 1.6-μm CoOx/Mo:BiVO4/Pd particles to slip into freshly opened micropores; solvent evaporation then shrinks the fibers, mechanically clamping the catalyst with <5 % loss after 20 cycles.
  • Mass-Transfer Leap: Surface-bound particles enjoy 4.2× faster O2 access and 19× higher H2O2 diffusion than matrix-embedded controls, pushing production to 7,700 μmol g-1 h-1—outpacing 90 % of reported catalysts.
  • Hydrophobic Shield: The 120.9° water-contact-angle surface limits H2O2 back-decomposition, yielding 0.53 mM in 2 h versus 0.12 mM for embedded designs.
  • Universal Toolkit: The same stretch-shrink protocol immobilized 800 nm RF523 spheres and hydrophilic variants, cutting fabrication cost by 39 %.

Real-World Validation

  • Micropollutant Blitz: Under 254 nm UV (1.08 mW cm-2), the membrane erased 95 % of 10 mg L-1 tetracycline or bisphenol A in 60 min—10× faster than UV alone—while mineralizing 70 % of total organic carbon.
  • Lake-to-Tap Resilience: Tests on lake water, tap water and secondary effluent all exceeded 90 % pollutant removal, with negligible activity loss in 5 mM Cl-, NO3- or humic acid.
  • Continuous-Flow Ready: A flow-by reactor (0.2 mL min-1) sustained 82 % tetracycline and 93 % BPA removal for 10 h with self-cleaning antifouling action.

Mechanistic Insights

  • Multi-Physics Modeling: Oxygen concentration profiles show severe starvation inside embedded catalyst layers, whereas SSPM maintains >0.8 mM O2 at the surface—critical for sustaining the 2-electron O2 reduction pathway.
  • ROS Mapping: Scavenger tests reveal ·OH and 1O2 dominate degradation; LC-MS identified 10 BPA and 9 TC intermediates, all eventually mineralized to CO2 and H2O.
  • Self-Defouling: In situ H2O2 continuously oxidizes membrane foulants, maintaining 95 % flux after 40 h of operation.

Economic & Regulatory Edge

  • Cost Model: At 10,000 m2 yr-1 production, SSPM is projected at $9.95 m-2—39 % cheaper than matrix-embedded equivalents and competitive with commercial PVDF.
  • Dry-Storage Advantage: Unlike embedded membranes that lose 40 % activity after 30 days dry storage, SSPM retains >95 % performance, simplifying logistics.
  • Regulatory Alignment: All materials are REACH-compliant, and the process uses only DMF and ethanol—solvents already approved for membrane manufacturing.

Scale-Up & Next Steps

  • Roll-to-Roll Pilot: A 1 m2 module under construction will integrate SSPM into a skid-mounted UV/H2O2 reactor for 10 m3 day-1 municipal pilot trials in Suzhou.
  • Hybrid AOPs: Coupling SSPM with low-pressure UV lamps enables on-site H2O2 generation + micropollutant destruction, eliminating chemical dosing and storage hazards.
  • Beyond Water: The stretch-shrink concept is being adapted for gas-phase VOC filters and self-sterilizing air-conditioning meshes.

By transforming passive membranes into active, self-armored reactors, the Li team delivers a plug-and-play upgrade for next-generation UV/H2O2 plants—cleaner water, lower cost, zero binders.

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Catalysis
Physical Sciences > Chemistry > Physical Chemistry > Catalysis
Materials for Energy and Catalysis
Physical Sciences > Materials Science > Materials for Energy and Catalysis
Photocatalysis
Physical Sciences > Materials Science > Materials for Energy and Catalysis > Photocatalysis
Nanoscale Design, Synthesis and Processing
Physical Sciences > Materials Science > Nanotechnology > Nanoscale Design, Synthesis and Processing
Chemical Synthesis
Physical Sciences > Chemistry > Chemical Synthesis
  • Nano-Micro Letters Nano-Micro Letters

    Nano-Micro Letters is a peer-reviewed, international, interdisciplinary and open-access journal that focus on science, experiments, engineering, technologies and applications of nano- or microscale structure and system in physics, chemistry, biology, material science, and pharmacy.