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Electronic Tuning of Metal Nanoparticles for Highly Efficient Photocatalytic Hydrogen Peroxide Production
摘要： We here present an innovative approach to increase the electron density of metallic Pd nanoparticles loaded on TiO2 photocatalysts by coordinating Pd with surface-anchored organic ligands. X-ray photoelectron spectroscopy and X-ray absorption near edge structure measurements confirm the negative charge on the Pd nanoparticle induced by electron donation from amine groups of the ligands. The electronically modified Pd on TiO2 exhibits unprecedentedly high photocatalytic H2O2 production from O2 reduction. Mechanistic investigations suggest that the enhanced performance results from electronic tuning of Pd nanoparticles, leading to enhanced charge separation on TiO2 support, improved activity of Pd nanoparticles as an oxygen reduction center, and improved selectivity for O2 reduction to produce H2O2.
关键词： immobilized organic ligands,oxygen reduction reaction,electronic tuning,hydrogen peroxide,photocatalysis
更新于2025-09-04 15:30:14
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The Development of Cocatalysts for Photoelectrochemical CO <sub/>2</sub> Reduction
摘要： The ever-increasing anthropogenic consumption of fossil fuels and the resulting large emission of CO2 have led to a severe energy crisis and climate change. Photocatalytic reduction of CO2 into fuels using solar energy is considered as a promising way to address these two problems. In particular, photoelectrochemical (PEC) reduction of CO2 can integrate and optimize the advantages of both photocatalysis and electrocatalysis for improved conversion efficiency and selectivity. In addition to the charge generation and separation, the efficient reduction of CO2 on the surface of a semiconductor-based photoelectrode remains a scientifically critical challenge, which can be greatly enhanced by the surface modification of cocatalysts. Herein, the recent developments of cocatalysts in PEC CO2 reduction over semiconductor-based photoelectrodes are described, and the basic principles of PEC CO2 reduction and the function of the cocatalyst in photoelectrocatalysis are discussed. The structure optimization between the photoelectrodes and the cocatalysts is also summarized since the loading of cocatalyst may shield the incident light and hinder charge transfer between them. Furthermore, the challenges and perspectives for PEC reduction of CO2 are also presented.
关键词： CO2 reduction,photoelectrochemical cells,cocatalysts,charge transfer
更新于2025-09-04 15:30:14
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Total Reflection Metasurface with Pure Modulated Signal
摘要： Metasurface has been proposed as one critical platform for orbital angular momentum (OAM) multiplexing. While metasurfaces have unique advantages to achieve light modulation with an ultrathin 2D layer, the relatively low transfer efficiency is a primary drawback. Such weakness leads to the mixing of unmodulated light into the output signal and greatly limits the functionality. A new design strategy is presented to fabricate self-filtering metasurface with pure signal light, which is computationally and experimentally verified on different applications, and it is also insensitive to the incident light polarization. Normal metasurface system requires bulky polarizer and filter, while our ultrathin design paves the way to multifunctional metasurface-based chip-scale circuits to replace the conventional bulky optical components. A proof-of-principle meta-cavity is designed to improve the transfer efficiency by 83%, while theoretical calculation shows 633% enhancement for an upgraded setup. This design can be widely applied to OAM optics, integrated photonics, optical sensing, data processing, and nanoimaging.
关键词： noise reduction,metasurfaces,nanophotonics,efficiency enhancement
更新于2025-09-04 15:30:14
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[IEEE 2018 2nd International Symposium on Multidisciplinary Studies and Innovative Technologies (ISMSIT) - Ankara, Turkey (2018.10.19-2018.10.21)] 2018 2nd International Symposium on Multidisciplinary Studies and Innovative Technologies (ISMSIT) - License Plate Recognition System by Using High Dimensional Model Representation
摘要： In this paper, it is proposed to match characters in content based images from real time scenes and extract the content as a text into the virtual environment by using the special called High Dimensional Model Representation (HDMR) for the system of License Plate Recognition. LPR is used to identify vehicles by reading license plates in image processing. Besides various techniques, a new matching algorithm is developed for the implementation of the LPR technology. LPR process is based on three major stages: Extraction of the license plate region from an image, segmentation of characters from the license plate region and recognition of characters which are segmented from the license plate. HDMR is used for working with high dimensional data based on image, at the stage of recognition of characters. The HDMR algorithm is used for matching the characters.
关键词： HDMR,character recognition,image processing,dimension reduction,license plate recognition
更新于2025-09-04 15:30:14
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Facile spraying fabrication of highly flexible and mechanically robust superhydrophobic F-SiO <sub/>2</sub> @PDMS coatings for self-cleaning and drag-reduction applications
摘要： Superhydrophobic coatings treated as surface functional materials are endowed with great application potential with respect to self-cleaning, drag-reduction, anti-icing, etc. In this study, we fabricated a highly flexible and mechanically robust superhydrophobic F-SiO2@PDMS coating through a facile layer-by-layer strategy. It was demonstrated that PDMS played a crucial role of binder for immobilizing the F-SiO2 nanoparticles and improving their adhesion to substrate materials. Meanwhile, the PDMS layer endowed the superhydrophobic coating with superior mechanical flexibility. Finally, the as-constructed superhydrophobic coating exhibited excellent water-repellency with a high water contact angle of 156.5° and low sliding angle of only 2.0°. Furthermore, the water adhesion strength on the superhydrophobic coating was only 2 mN, indicating its ultralow viscous resistance to dynamic moving water droplets. The superhydrophobic F-SiO2@PDMS coating was independent of the substrates without any limitations, and they exhibited high flexibility and mechanical robustness with the elongation ratio reaching 83.3% under the conditions of high superhydrophobicity. Also, the superhydrophobic coating exhibited strong durability under the severe environments of corrosion and mechanical abrasion. Thus, the as-fabricated highly flexible and mechanically robust superhydrophobic F-SiO2@PDMS coating is considered to be an ideal candidate for applications in the fields of self-cleaning and drag-reduction.
关键词： F-SiO2@PDMS,drag-reduction,mechanical robustness,superhydrophobic coatings,self-cleaning
更新于2025-09-04 15:30:14
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Reduced Graphene Oxide Nanostructures by Light: Going Beyond the Diffraction Limit
摘要： Graphene oxide (GO) offers excellent possibilities that are recently demonstrated in many applications ranging from biological sensors to optoelectronic devices. The process of thermal annealing aids in removing the oxygen-containing groups in GO, making GO more graphene-like, or the so-called reduced graphene oxide (rGO). Thermal reduction can also be achieved by intense light. Here, we demonstrate a scalable, inexpensive, and environmentally friendly method to pattern graphene oxide films beyond the diffraction limit of light using a conventional laser. We show that contrary to previous reports, non-linear effects that occur under high intensity conditions of laser irradiation allow the fabrication of highly conductive carbon nanowires with dimensions much smaller than the laser spot size. The potential of this method is illustrated by the fabrication of several devices on flexible and transparent substrates, including hybrid plasmonic/rGO sensors.
关键词： reduced graphene oxide,optoelectronic devices,laser reduction,Graphene oxide,diffraction limit
更新于2025-09-04 15:30:14
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Synthesis and Characterizations of Zinc Oxide on Reduced Graphene Oxide for High Performance Electrocatalytic Reduction of Oxygen
摘要： Electrocatalysts for the oxygen reduction (ORR) reaction play an important role in renewable energy technologies, including fuel cells and metal-air batteries. However, development of cost effective catalyst with high activity remains a great challenge. In this feature article, a hybrid material combining ZnO nanoparticles (NPs) with reduced graphene oxide (rGO) is applied as an efficient oxygen reduction electrocatalyst. It is fabricated through a facile one-step hydrothermal method, in which the formation of ZnO NPs and the reduction of graphene oxide are accomplished simultaneously. Transmission electron microscopy and scanning electron microscopy profiles reveal the uniform distribution of ZnO NPs on rGO sheets. Cyclic voltammograms, rotating disk electrode and rotating ring disk electrode measurements demonstrate that the hierarchical ZnO/rGO hybrid nanomaterial exhibits excellent electrocatalytic activity for ORR in alkaline medium, due to the high cathodic current density (9.21 × 10?5 mA/cm2), positive onset potential (?0.22 V), low H2O2 yield (less than 3%), and high electron transfer numbers (4e from O2 to H2O). The proposed catalyst is also compared with commercial Pt/C catalyst, comparable catalytic performance and better stability are obtained. It is expected that the ZnO/rGO hybrid could be used as promising non-precious metal cathode in alkaline fuel cells.
关键词： reduced graphene oxide,zinc oxide,non-precious-metal catalyst,oxygen reduction reaction
更新于2025-09-04 15:30:14
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Graphene Based Poly(Vinyl Alcohol) Nanocomposites Prepared by In Situ Green Reduction of Graphene Oxide by Ascorbic Acid: Influence of Graphene Content and Glycerol Plasticizer on Properties
摘要： The enhanced properties of polymer nanocomposites as compared with pure polymers are only achieved in the presence of well-dispersed nano?llers and strong interfacial adhesion. In this study, we report the preparation of nanocomposite ?lms based on poly(vinyl alcohol) (PVA) ?lled with well dispersed graphene sheets (GS) by in situ reduction of graphene oxide (GO) dispersed in PVA solution using ascorbic acid (L-AA) as environmentally friendly reductant. The combined effect of GS content and glycerol as plasticizer on the structure, thermal, mechanical, water absorption, and water barrier properties of PVA/GS nanocomposite ?lms is studied for the ?rst time. Higher glass transition temperature, lower crystallinity, melting, and crystallization temperature, higher mechanical properties, and remarkable improvement in the thermal stability compared to neat PVA are obtained as a result of strong interfacial interactions between GS and PVA by hydrogen bonding. PVA/GS composite ?lm prepared by ex situ process is more brittle than its in situ prepared counterpart. The presence of GS improves the water barrier and water resistance properties of nanocomposite ?lms by decreasing water vapor permeability and water absorption of PVA. This work demonstrates that the tailoring of PVA/GS nanocomposite properties is enabled by controlling GS and glycerol content. The new developed materials, particularly those containing plasticizer, could be potential carriers for transdermal drug delivery.
关键词： nanocomposites,graphene oxide green reduction,glycerol,graphene,poly(vinyl alcohol)
更新于2025-09-04 15:30:14
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Ultrathin Co0.85Se nanosheet cocatalyst for visible-light CO2 photoreduction
摘要： Ultrathin Co0.85Se nanosheets were prepared via a facile solvothermal method, which successfully overcome the disadvantage of insu?cient active sites in bulk Co0.85Se by reducing its thickness into the atomic scale. Co0.85Se nanosheets have been found to be e?cient cocatalysts for photocatalytic CO2 reduction with TON as high as 58 in 1 h reaction under visible-light irradiation. Compared with bulk Co0.85Se blocks, the ultrathin nanosheet samples exhibited nearly 2.5 times higher activity in CO2 photoreduction. The metal-like character and ultrathin 2D structure of Co0.85Se nanosheets support the superb charges transfer and rich CO2 adsorption sites exposure for surface catalysis. A relationship between the surface structure and the cocatalytic activity was established. These results not only demonstrate the potential of a notable, a?ordable and earth-abundant CO2 photoreduction cocatalyst based on ultrathin Co0.85Se nanosheets but also provide a guidance in the exploration of excellent active and durable cocatalysts/catalysts to replace noble metals for arti?cial photosynthesis.
关键词： Photocatalysis,Cocatalyst,Co0.85Se nanosheets,CO2 reduction
更新于2025-09-04 15:30:14
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Revisiting structural and photocatalytic properties of g-C3N4/TiO2: Is surface modification of TiO2 by calcination with urea an effective route to “solar” photocatalyst?
摘要： g-C3N4/TiO2 derived from the surface modification of TiO2 by calcination with urea has been widely studied as a “visible-light-active” photocatalyst for environmental purification applications. However, few attentions have been paid to the structure characterization and the photocatalytic properties of the resultant nanocomposite photocatalysts under a practical sunlight irradiation. Here we employ various characterization techniques, including TGA, XRD, TEM, XPS, UV-Vis spectrum, and N2-sorption analysis to characterize the evolutions in phase crystal structure, microstructure and optical properties of g-C3N4/TiO2 nanohybrids synthesized through calcining a mechanical mixture of urea and Evonik Aeroxide P-25 TiO2 (P25) at 350-500 oC. The thermal pyrolysis of urea leads to the surface decoration of TiO2 with graphitic carbon nitrate (g-C3N4) at temperatures above 400 oC. The photocatalytic properties of the resultant g-C3N4/TiO2 nanoparticles are evaluated through photocatalytic decoloration of methylene blue (MB) and reduction of Cr(VI) to Cr(III) under visible (420 nm), UV (365 nm), and simulated solar light irradiations. The nanohybrid photocatalysts, as most previous studies reported, show much higher photocatalytic activity under visible light irradiation than the single-component counterparts, i.e. P25 or g-C3N4. However, under solar and UV irradiation, no considerable improvements are found, which is caused by the decrease in redox potential upon interfacial charge carrier transfer between g-C3N4 and TiO2. Moreover, g-C3N4/TiO2 shows an ultralow photocatalytic activity in Cr(VI) reduction. The surface modification with organic g-C3N4 is assumed to tune the surface properties (e.g. hydrophilicity) of TiO2. Our results demonstrate that photocatalytic activity in UV range is as important as that in visible range, and developing efficient “solar” photocatalysts should balance both since they might be incompatible with each other.
关键词： graphitic carbon nitrate,dye degradation,TiO2 nanoparticles,Cr (VI) reduction,semiconductor photocatalysis,Aeroxide P25,charge carrier transfer
更新于2025-09-04 15:30:14