High-Efficiency Photocatalytic H₂O₂ Production in a Dual Optical– and Membrane–Fiber System

Abstract

Hydrogen peroxide (H 2 O 2 ) is widely used for industrial applications. Currently, ∼95% of H 2 O 2 production employs the energyand chemical-intensive anthraquinone oxidation process. Photocatalytic H 2 O 2 production is an emerging alternative process. While advanced material discovery has been a primary focus of photocatalysis, breakthroughs in reactor designs capable of supporting novel materials are lacking. To enable low-energy and chemical-free photocatalytic production of H 2 O 2 , we integrated visible-light-emitting diodes (41 mW cm −2 ), optical fibers, and O 2 -delivering hollow-fiber membranes. A stable iron-based metal−organic framework photocatalyst (MIL-101(Fe)) activated by visible light was permanently affixed to the optical fiber, resulting in a uniform and high specific surface area (2650 m 2 g −1 ). The combination of photocatalytic optical fiber and O 2permeable hollow-fiber membranes is a novel architecture for improving light utilization, photocatalyst reuse, and O 2 supply. The H 2 O 2 production rate in pure water was as high as 290 mM h −1 catalyst-g −1 , which is as much as 60-fold greater than the bestreported values using photocatalytic slurries. The efficient delivery of light also achieved a low energy cost for H 2 O 2 production (2.3 kWh kgH 2 O Hd 2 Od 2 −1), and its production rate could be sustained for at least five repeated cycles (2 h per cycle). Energy-efficient H 2 O 2 production without chemical inputs makes the dual-fiber system a more sustainable option for H 2 O 2 production.

Boosting Hydrogen Production via Water Splitting: An ITO Plus g-C3N4 Nanomaterial Enabled Polymer Optical Fiber Design

“…This configuration achieves a remarkable space density of 2,670 m 2 m –3 , which is >25 times greater than that of a conventional PEC reactor with a plate-shaped electrode (3 cm width ×30 cm length ×1 cm thickness), and approximately 70 times greater than a recently commercialized hydrogen production plant using a solar-driven photocatalyst-immobilized design for water splitting . Beyond the competitive space efficiency, our PEC–POF design offers additional benefits such as the low cost of POF (less than $0.10 USD per meter) versus glass plates, low cost ITO nanoparticles versus chemical-vapor deposition on flat plates, physical flexibility of POF allowing easy bending, and compatibility with various light sources and photocatalysts. ,,− These features make it a highly competitive alternative for large-scale hydrogen production.…”

“…The application of ITO plus g-C 3 N 4 coatings significantly improves the side-emission capabilities of bare POFs, leading to enhanced light utilization efficiency within the nanomaterial cladding layer. As demonstrated in Figure a, the total light input ( I 0 , μW cm –2 ) at the proximal end of the fiber entering the optoelectrode can be represented according to the following formula: , I 0 = I Abs + I S + I U + I T where I Abs is light irradiance absorbed by bare POF materials (PMMA/PVDF), I S is the side-emitted light due to scattering, I U is the light irradiance absorbed and utilized by the nanomaterials within the polymer cladding, and I T is the transmitted light irradiance from the distal end of the optoelectrode. The light intensity measurement method is detailed in Appendix S5.…”

“…However, by utilizing bundles of many parallel optoelectrodes, we could potentially amplify hydrogen production several-fold by increasing the irradiated surface area (m 2 ) while maintaining low packing geometry requirements for a large-scale reactor (m 3 ). This geometric packing density (m 2 fiber surface area per m 3 reactor volume) is used in other optical fiber designs as well as flat-sheet or hollow-fiber membrane separation processes. , As demonstrated in Figure , our prototype uses a single optoelectrode (1.5 mm diameter, 20 cm length), which could readily be scaled up to a bundle of 400 optoelectrodes in a tubular reactor (15 cm diameter, 20 cm length). This configuration achieves a remarkable space density of 2,670 m 2 m –3 , which is >25 times greater than that of a conventional PEC reactor with a plate-shaped electrode (3 cm width ×30 cm length ×1 cm thickness), and approximately 70 times greater than a recently commercialized hydrogen production plant using a solar-driven photocatalyst-immobilized design for water splitting .…”

Ligand Functionalization of Metal‐Organic Frameworks for Photocatalytic H2O2 Production

“…Based on the relative studies, the water/benzyl alcohol two-phase system, [18] membranes in a gas-membrane-gas mode, [14] all-in-one photocatalysis device with bilayer structure [31] and architecture with dual-fiber system deserve to be learned. [32] In all, ligand functionalization of MOFs highly deserves to be continually and deeply studied for photocatalytic H 2 O 2 production, and we hoped that this concept could offer insight and guidance for both MOF design and H 2 O 2 production.…”

Large‐Scale Continuous and In Situ Photosynthesis of Hydrogen Peroxide by Sulfur‐Functionalized Polymer Catalyst for Water Treatment

“…In addition to the catalyst design, the development of the photocatalytic reactor is another crucial factor limiting the practical application of photocatalytic H 2 O 2 production. Although laboratory‐scale H 2 O 2 production using suspension system, [13] fluid triphase system, [14] and dual‐fiber reactor [15] have been reported, these reactors still face obstacles such as catalyst recovery, continuous oxygen bubbling, high cost, and difficult to scale up [16] . The use of panel reactor for sunlight‐driven scale‐up H 2 O 2 production becomes a promising trend.…”