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Electron Diffusion Length and Charge Separation Efficiency in Nanostructured Ternary Metal Vanadate Photoelectrodes
摘要： Ternary metal vanadates have recently emerged as promising photoelectrode materials for sunlight-driven water splitting. Here, we show that highly active nanostructured BiVO4 films can be deposited onto fluorine-doped tin oxide (FTO) substrates by a facile sequential dipping method known as successive ionic layer adsorption and reaction (SILAR). After annealing and deposition of a cobalt phosphate (Co-Pi) co-catalyst, the photoelectrodes produce anodic photocurrents (under 100 mW cm-2 broadband illumination, 1.23 V vs. RHE) in pH 7 phosphate buffer that are on par with the highest reported in the literature for similar materials. To gain insight into the reason for the good performance of the deposited films, and to identify factors limiting their performance, incident photon-to-electron conversion efficiency spectra have been analyzed using a simple diffusion–reaction model to quantify the electron diffusion length (Ln; the average distance travelled before recombination) and charge separation efficiency (ηsep) in the films. The results indicate that ηsep approaches unity at sufficiently positive applied potential but the photocurrent is limited by significant charge collection losses due to a short Ln relative to the film thickness. The Co-Pi catalyst is found to improve ηsep at low potentials as well as increase Ln at all potentials studied. These findings help to clarify the role of the Co-Pi co-catalyst and show that there could be room for improvement of BiVO4 photoanodes deposited by SILAR if Ln can be increased.
关键词： charge separation efficiency,ternary metal vanadates,SILAR,electron diffusion length
更新于2025-09-23 15:22:29
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Role of nitrogen doped carbon quantum dots on CuO nano-leaves as solar induced photo catalyst
摘要： A p-type transition metal oxide, copper oxide (CuO) was modified with nitrogen doped carbon quantum dots (NCQDs) to fabricate an effective CuO/NCQDs solar driven photo catalyst. The fabrication of single phase monoclinic CuO was confirmed by XRD. SEM images showed the leaf like morphology for CuO which appeared rough and densely packed in CuO/NCQDs composites. TEM images of CuO/NCQDs shows slightly distorted nano-leaves with NCQDs dispersed on them. HRTEM of CuO/NCQDs shows fringes with characteristic planes confirming that the addition of NCQDs has not distorted the crystal structure of CuO. SAED of CuO/NCQDs further confirms the crystalline nature of the as synthesized composite photo catalyst by exhibiting bright diffraction rings. These results further supported the XRD data. EDS spectra of NCQDs and CuO/NCQDs confirm the formation of pure nitrogen doped carbon quantum dots and Cu, N, C and O atoms confirming that NCQDs are well incorporated on CuO Nano leaves. UV-Vis spectra showed a slight increase of band gap energies due to quantum confinement effects. PL spectra exhibited decreased photoluminescence intensity indicating suppression of recombination rate. The developed photocatalyst was applied for the degradation of harmful dye methyl orange. The composite catalyst showed superior degradation efficiency as compared to pure CuO nano-leaves attributed to enhanced visible light absorption and better charge separation ability due to introduction of NCQDs.
关键词： solar light catalyst,nitrogen doped quantum dots,charge separation efficiency,quantum confinement effect,CuO nano-leaves
更新于2025-09-19 17:13:59
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Preparation of Nb2O5-decorated hierarchical porous ZnO microspheres with enhanced photocatalytic degradation of palm oil mill effluent
摘要： In the present work, Nb2O5-decorated hierarchical porous ZnO microspheres (ZnO/Nb2O5) were successfully prepared through a facile surfactant-free method. The as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy and Brunauer–Emmett–Teller surface area analyses. Under UV light irradiation, the ZnO/Nb2O5 composites degraded palm oil mill effluent (POME) efficiently and demonstrated much higher photocatalytic activity compared to those of pure ZnO and Nb2O5. The enhanced photocatalytic degradation performance of ZnO/Nb2O5 composites was attributed to the high charge separation efficiency and hydroxyl radical generation ability as verified by the photoluminescence spectra. Phytotoxicity test upon the POME degradation over ZnO/Nb2O5 photocatalysis considerably decreased through the measurement of radicle lengths of Vigna radiata. Moreover, the ZnO/Nb2O5 composites were reused several times without appreciable loss of activity. This work revealed that the as-prepared ZnO/Nb2O5 composites have great potential for practical applications in the field of wastewater treatment.
关键词： Nb2O5-decorated hierarchical porous ZnO microspheres,Photocatalytic degradation,Charge separation efficiency,Palm oil mill effluent,Hydroxyl radical generation
更新于2025-09-10 09:29:36