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A New Ag/AgBr/LaAlO3 Plasmonic Composite: Synthesis, Characterization, and Visible-Light Driven Photocatalytic Activity
摘要： In recent years, fabricating the visible-light induced photocatalysts based on the concept of plasmonic photocatalysis provides an efficient way to reduce environmental pollution. Accordingly, the present investigation has been carried out to develop such materials based on lanthanum aluminate (LaAlO3; LAO) and Ag/AgBr. The Ag/AgBr/LAO composite is prepared by deposition of metallic Ag nanoparticles onto the pre-prepared AgBr/LAO heterostructure by visible-light photo-reduction. The characteristic properties of synthesized catalysts were investigated by using a variety of techniques such as XRD, N2 adsorption–desorption, FESEM/EDX/EDS mapping, TEM-HRTEM, UV–Vis DRS, FT-IR, XPS, and PL measurements. The photocatalytic degradation of methylene blue (MB) was used as a probe reaction to evaluate their photocatalytic activity under visible-light irradiation. Because of the higher surface area with vast mesoporous nature, enhanced visible light absorption, and more efficient charge separation after the deposition of Ag/AgBr, the composite Ag/AgBr/LAO showed enhanced photocatalytic activity compared with pristine LAO. The recycling experiment revealed excellent stability (up to five successive cycles) of Ag/AgBr/LAO composite. Furthermore, a photocatalytic mechanism is proposed for the degradation of MB over Ag/AgBr/LAO composite. The composite Ag/AgBr/LAO can be used as a promising catalyst for environmental remediation.
关键词： charge separation,methylene blue,Ag/AgBr,plasmonic Ag nanoparticles,nanocomposite,LaAlO3
更新于2025-09-23 15:19:57
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Analysis of the charge transfer and separation in electrically doped organic semiconductors by electron spin resonance spectroscopy
摘要： We investigated the charge generation mechanism of electrically doped organic semiconductors (OSs) by electron spin resonance (ESR) analysis. ESR spectroscopy was used to successfully evaluate the radical density of p-doped OSs to estimate the charge transfer efficiency (CTE) of various doped systems. The results showed that the CTE is efficient close to 100% if the dopant molecules are homogenously dispersed and the energy difference (?E) between the highest occupied molecular orbital (HOMO) level of the host molecule and lowest unoccupied molecular orbital (LUMO) level of the p-dopant is large. The charge separation efficiency to form free carriers from the radicals is rather low (less than 12% in this study) and is a dominant factor controlling the charge generation efficiency (CGE). An organic dopant molybdenum tris[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] turns out to be an efficient dopant with the CGE of 9.7% due to high CTE originating from homogenous dispersion of the organic p-dopants and low LUMO level, i.e., large ?E.
关键词： charge generation efficiency,p-dopant,charge transfer,electron spin resonance spectroscopy,Organic semiconductors,charge separation
更新于2025-09-19 17:15:36
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Elucidating Charge Separation in Particulate Photocatalysts Using Nearly-Intrinsic Semiconductors with Small Asymmetric Band Bending
摘要： Photocatalytic water splitting using particulate suspensions is a promising approach for achieving large-scale production of renewable hydrogen fuels. Previous studies have hypothesized that band energy levels of such photocatalysts in water are both flat and symmetrical, and the charge separation in such photocatalysts is driven by random charge carrier diffusion. However, it is not well understood how the observed asymmetry of carrier diffusion is achieved during photocatalysis. To fully understand this charge separation process, we used double-side polished, intrinsic silicon as a model light absorber and manipulated the direction of charge-carrier diffusion using combinations of carrier-selective contacts. Degenerately p-type doped and n-type doped silicon, along with as-grown and annealed TiO2 overlayers grown by atomic layer deposition, were used as carrier selective back and front contacts, respectively. The protective TiO2 layers along with nickel oxide co-catalysts enabled bi-functional, stable silicon photoelectrodes for photoelectrochemical hydrogen evolution and water oxidation in alkaline solution. A device simulation was applied to analyse the experimental results and further gain understandings on the charge separation process in photocatalysts involving semiconductor/liquid junctions. Combined experimental and simulation study indicated that the contacts established asymmetric band bending inside the intrinsic silicon layer and drove the directional charge separation, primarily carrier diffusion. By scaling down the thickness of the silicon layer in the simulation, analogies of charge separation in particulate photocatalysts can be drawn. Based on the understandings from intrinsic silicon, we further revealed that photocatalysts generally do require asymmetric band bending to drive diffusional charge separation, and that a small band edge offset of 0.45 eV between reductive and oxidative catalytic sites can build a sufficient, steady-state photovoltage of over 1.23 V for overall water splitting by using a model SrTiO3 absorber. It provides an insightful guidance for designing efficient and stable particulate photocatalysts especially those using Si and III-V semiconductors with protective layers such as TiO2.
关键词： Carrier-selective contact,Particulate photocatalyst,Charge separation
更新于2025-09-19 17:15:36
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Ferrocene Linkage Facilitated Charge Separation in Conjugated Microporous Polymers
摘要： Conjugated microporous polymers (CMPs) have full access to the organic synthesis toolbox and feature-rich functionality, structural diversity, and high surface area. We incorporated ferrocene (Fc) into the backbones of CMPs and systematically engineered their optical energy gaps. Compared with the CMPs without Fc units yet adopting similar molecular orbital level, Fc-based CMPs can sufficiently generate reactive oxygen species (ROS) under visible light. The resultant ROS are able to effectively decompose the absorbed pollutants, including organic dyes and chemical warfare agents. Specifically, Fc-based CMPs significantly outperform commercial TiO2 (P25) in the degradation of methylene blue and are capable of converting 2-chloroethyl ethyl sulfide (a mustard gas simulant) into completely nontoxic product.
关键词： conjugated microporous polymer,charge separation,photocatalytic degradation,ferrocene,reactive oxygen species
更新于2025-09-19 17:15:36
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Significant enhancement of stability for visible photocatalytic overall water splitting by assembling ultra-thin layer of NiO over Zn1-xCdxSX
摘要： Solar light driven water splitting into hydrogen and oxygen using visible light active photocatalyst has been considered as a clean, green, and renewable route to solar energy conversion and storage. Although Zn1-xCdxS catalyst shows comparatively higher activity for photocatalytic hydrogen generation under visible light irradiation, it suffers serious photocorrosion during the photocatalytic reaction. Deposition of protection layer over Zn1-xCdxS catalyst is believed to be an effective way to inhibit such photocorrosion. Nevertheless, seldom of protection layer exhibits satisfied catalytic properties for hydrogen evolution while presents good protection ability. In this work, a new Zn1-xCdxS photocatalyst has been developed for water splitting under visible light illumination by assembled an ultra-thin NiO layer over Zn0.8Cd0.2S via in-situ photodeposition method. By this strategy, NiO/Zn0.8Cd0.2S showed significant higher activity than Pt/Zn0.8Cd0.2S under same conditions without photocorrosion. The AQE of 0.66% for hydrogen evolution at 430 nm has been achieved and multi-cycle stability has been accomplished up to 12 hours without significant decay. Moreover, the strong electronic coupling between NiO layer and Zn1-xCdxS promoted efficient charge separation and migration.
关键词： Overall water splitting,sulfide semiconductor photocatalyst with thin NiO catalytic layer,enhanced charge separation and migration,significant enhanced stability,anti-photocorrosion
更新于2025-09-19 17:15:36
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A Type II n-n staggered orthorhombic V2O5/monoclinic clinobisvanite BiVO4 heterojunction photoanode for photoelectrochemical water oxidation: Fabrication, characterisation and experimental validation
摘要： Conventional photoanode using a singular semiconductor material is not technically viable for photoelectrochemical (PEC) water oxidation owing to the properties relating to its wide band gap, sluggish charge mobility, as well as poor separation and rapid recombination of photogenerated charge carriers. The main aim of this study was to fabricate an n-n heterojunction photoanode of V2O5/BiVO4 via a facile electrodeposition synthesis method in order to overcome the technical bottlenecks encountered in conventional singular photoanode structures. Additionally, the synergistic effect of band potentials matching and conductivity difference between BiVO4 and V2O5 were studied using LSV, IMPS, EIS, HR-TEM, XRD, XPS, Raman and ultraviolet-visible spectroscopies. This was followed by the performance evaluation of the light-induced water splitting using a standard three-electrode assembly PEC cell under 1.5 AM solar simulator. Results showed that the V2O5/BiVO4 heterojunction photoanode achieved a significantly improved photocurrent density of 1.53 mA/cm2 at 1.5 V vs Ag/AgCl, which was a 6.9-fold and a 7.3-fold improvement over the individual pristine BiVO4 (0.22 mA/cm2) and V2O5 (0.21 mA/cm2), respectively. The improvement was attributed to the lower charge resistances at the FTO/semiconductor, semiconductor/FTO and semiconductor/electrolyte interfaces as well as the fast transit time (τ) of 6.4 millisecond for photo-injected electrons in the V2O5/BiVO4 heterojunction photoanode. Finally, the experimental results were used to reconstruct a theoretical band diagram in validating the heterojunction alignment between V2O5 and BiVO4 as well as in elucidating the photogenerated charge carriers transfer mechanism in the V2O5/BiVO4 heterojunction photoanode.
关键词： Bismuth vanadate,n-n heterojunction,Charge separation,Photoelectrocatalysis
更新于2025-09-19 17:15:36
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Extending the ?-electron conjugation in 2D planar graphitic carbon nitride: Efficient charge separation for overall water splitting
摘要： We report the direct overall pure water splitting by visible light excited graphitic carbon nitride incorporated with conjugated aromatic rings without using sacrificial agents. We fabricated the modified graphitic carbon nitride polymer samples by copolymerization of melamine with 2,4,6-triaminopyrimidine and 1,3,5-triaminobenzene, containing a few-carbon (pyrimidine) to all-carbon (benzene) aromatic rings. Solid state 13C NMR shows that the core molecular skeleton of g-C3N4 remained intact even after the incorporation of benzene and pyrimidine aromatic rings into g-C3N4 chemical structure. Upon substitution of benzene aromatic ring in the place of triazine ring, the optical band gap energy of g-C3N4 is narrowed down from 2.8 eV to 2.1 eV with negative shifts of valence and conduction bands and due to the formation of defects like nitrogen vacancies. The DFT calculations predict that the benzene doped carbon nitride polymer has localized charge densities over valence band maxima and conduction band minima in different parts of heptazine rings, which assist in reducing the recombination rate of the charge carriers. The benzene ring incorporated carbon nitride photoelectrode shows higher photocurrent with lesser charge transfer resistance than the parent g-C3N4 and pyrimidine doped g-C3N4 polymers. This demonstrates the importance of the extended conjugation in g-C3N4 due to the presence of aromatic benzene rings. This is further corroborated by photoluminescence and electron paramagnetic resonance measurements. As a result, the benzene ring incorporated carbon nitride is more active than the pyrimidine ring incorporated carbon nitride for solar water splitting. The benzene ring incorporated carbon nitride polymer directly splits water and generates about 7 μmol h-1 of hydrogen with apparent quantum yield of 1.6% at 450 nm in the absence of sacrificial reagents, achieving turnover number of 1.6.
关键词： turnover number,benzene,DFT calculations,Carbon nitride,apparent quantum yield,charge separation,pyrimidine,water splitting
更新于2025-09-19 17:15:36
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Rectifying Behaviour and Photocatalytic Activity in ZnO Nanorods Array/Ag/CuSe Heterostructure
摘要： Ag incorporated vertically aligned ZnO nanorods array/CuSe thin film (ZnO NRs/CuSe TF) have been fabricated via a solution route, thermal evaporation and magnetron sputtering process. Ternary ZnO nanorods/Ag/CuSe heterostructure was studied by X-ray diffractometry, field emission-scanning electron microscopy/energy dispersive X ray spectroscopy, current–voltage measurement and a UV–Vis–near IR spectrophotometer. The photocatalytic performance was estimated by the degradation of Rhodamine B solution under UV–Vis light irradiation. The photocatalytic efficiency of the ZnO NRs/Ag/CuSe heterostructure is higher than that of ZnO NRs/Ag and ZnO NRs/CuSe counterparts due to the robust effects of the three functional components coupling. The localized surface plasmon resonance and two Schottky junctions (e.g. Ag/ZnO and Ag/CuSe) motivates photogenerated electron–hole separation and transfer. This work presents an artificial manipulated system to enhance light harvesting, efficient charge separation and transfer, and low recombination rate in solar energy conversion.
关键词： Photocatalytic activity,Localized surface plasmon resonance (LSPR),Charge separation,ZnO nanorods array/Ag/CuSe heterostructure
更新于2025-09-19 17:15:36
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Radial Nanowire Assemblies under Rotating Magnetic Field Enabled Efficient Charge Separation
摘要： Developing efficient charge separation strategies is essential to achieve high power conversion efficiency in fields of chemistry, biology and material science. Herein, we develop a facile strategy for fabrication of unique wafer-scale radial nanowire assemblies by exploiting shear force in rotary solution. The assembling mechanism can be well revealed by the large-scale stochastic dynamics simulation. Free electrons can be rapidly generated to produce quantitatively tunable current output when the radial nanowire assemblies rotating under the magnetic field. Moreover, the photoconductive performance of the radial semiconductor nanowire assemblies can be remarkably enhanced as the electron-hole recombination was retrained by the efficient charge separation under the rotating magnetic field. Such large-scale unique nanowire assemblies will facilitate the design of efficient charge separation process in bio-system, sensors and photocatalysis.
关键词： nanowires,charge separation,stochastic dynamics simulation,assembly,magnetic field
更新于2025-09-19 17:13:59
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Photoinduced Chirality Switching of Metal-Inorganic Plasmonic Nanostructures
摘要： Chiral plasmonic nanodevices whose handedness can be switched reversibly between right and left by external stimulation have attracted much attention. However, they require delicate DNA nanostructures and/or continuous external stimulation. In this study, those issues are addressed by using metal-inorganic nanostructures and photoinduced reversible redox reactions at the nanostructures, namely site-selective oxidation due to plasmon-induced charge separation (PICS) under circularly polarized visible light (CPL) and reduction by UV-induced TiO2 photocatalysis. We irradiate gold nanorods (AuNRs) supported on TiO2 with right- or left-CPL to generate electric fields with chiral distribution around each AuNR, and to deposit PbO2 at the sites where the electric fields are localized, for fixing the chirality to the AuNR. The nanostructures thus prepared exhibit circular dichroism (CD) based on longitudinal and transverse plasmon modes of the AuNRs. Their chirality given by right-CPL (or left-CPL) is locked until PbO2 is re-reduced under UV light. After unlocking by UV, the chirality can be switched by left-CPL (or right-CPL) irradiation, resulting in reversed CD signals and locking the switch again. The handedness of the chiral plasmonic nanodevice can be switched reversibly and repeatedly.
关键词： plasmon-induced charge separation,circular dichroism,chiral plasmonic nanodevice,nanofabrication,circularly polarized light
更新于2025-09-19 17:13:59