Evanescent waves modulate energy efficiency of photocatalysis within TiO2 coated optical fibers illuminated using LEDs

Abstract

Coupling photocatalyst-coated optical fibers (P-OFs) with LEDs shows potential in environmental applications. Here we report a strategy to maximize P-OF light usage and quantify interactions between two forms of light energy (refracted light and evanescent waves) and surface-coated photocatalysts. Different TiO2-coated quartz optical fibers (TiO2-QOFs) are synthesized and characterized. An energy balance model is then developed by correlating different nano-size TiO2 coating structures with light propagation modes in TiO2-QOFs. By reducing TiO2 patchiness on optical fibers to 0.034 cm2/cm2 and increasing the average interspace distance between fiber surfaces and TiO2 coating layers to 114.3 nm, refraction is largely reduced when light is launched into TiO2-QOFs, and 91% of light propagated on the fiber surface is evanescent waves. 24% of the generated evanescent waves are not absorbed by nano-TiO2 and returned to optical fibers, thus increasing the quantum yield during degradation of a refractory pollutant (carbamazepine) in water by 32%. Our model also predicts that extending the TiO2-QOF length could fully use the returned light to double the carbamazepine degradation and quantum yield. Therefore, maximizing evanescent waves to activate photocatalysts by controlling photocatalyst coating structures emerges as an effective strategy to improve light usage in photocatalysis.

Near-Ultraviolet Light-Driven Photocatalytic Chlorine Activation Process with Novel Chlorine Activation Mechanisms

“…We recently reported a visible-light-driven graphitic carbon nitride (g-C 3 N 4 ) photocatalytic chlorine activation process (Vis/g-C 3 N 4 /chlorine process) that degraded carbamazepine (CBZ) at a rate constant 16 and 7 times higher than that without g-C 3 N 4 and HOCl/ClO – , respectively. The Vis/g-C 3 N 4 /chlorine process possessed a CBZ degradation quantum yield of 0.1%, which is comparable with those of the UVC/chlorine and UV/H 2 O 2 AOPs. , Compared with O 3 , H 2 O 2 , PMS, and PDS, chlorine is a better alternative, because it has been widely used in drinking water treatment as a low-cost disinfectant. The unreacted chlorine after the process provides residual protection in the drinking water distribution system.…”

“…The Vis/g-C 3 N 4 /chlorine process possessed a CBZ degradation quantum yield of 0.1%, which is comparable with those of the UVC/chlorine and UV/ H 2 O 2 AOPs. 6,7 Compared with O 3 , H 2 O 2 , PMS, and PDS, chlorine is a better alternative, because it has been widely used in drinking water treatment as a low-cost disinfectant. The unreacted chlorine after the process provides residual protection in the drinking water distribution system.…”

Upconversion under Photon Trapping in ZnO/BN Nanoarray: An Ultrahigh Responsivity Solar‐Blind Photodetecting Paper

“…As we know, in principle, the penetration depth of light in a matter is proportional to the photon wavelength. [ 37 ] Here the abnormal propagation depth could be understood as following. The bandgap of wurtzite ZnO is 3.4 eV (365 nm).…”

Application of Spinel and Hexagonal Ferrites in Heterogeneous Photocatalysis

“…This review presents all the aspects, focusing on the newest trends, applied for the use of spinel and hexagonal ferrites (selected groups of ferromagnets) in heterogeneous photocatalysis, as an efficient method for semiconductor recycling. Of course, other types of separation/recycling have been proposed and investigated, such as sedimentation, coagulation, (ultra)filtration, immobilization of photocatalysts on elements of photoreactors (walls [16], quartz protecting tubes of lamps and LEDs [17,18], and optical fibers [19]) or additional supporters (glass beads [16], microspheres [20], balls [21], mesh [22], cloth [22], rings [23], membranes [24][25][26], and plates/films/foils [27][28][29][30]) [31].…”