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A Combined Experimental and Theoretical Insights into the Synergistic Effect of Cerium Doping and Oxygen Vacancies into BaZrO <sub/>3-δ</sub> Hollow Nanospheres for Efficient Photocatalytic Hydrogen Production
摘要： The long-standing debate over the influence of oxygen vacancies and various dopants has been the center point in perovskite-based compounds for their photocatalytic applications. Hydrothermally synthesized Cerium doped BaZrO3 (BZO) hollow nanospheres has been systematically studied by experimental and theoretical calculations to understand the effect of Cerium doping and oxygen vacancies on the photocatalytic properties. Compounds synthesized by a template-free route were composed of hollow nanospheres generated by Ostwald ripening of spherical nanospheres, which were formed by agglomeration of nanoparticles. The high alkaline condition and high temperature during the hydrothermal condition may lead to the formation of local disorders and oxygen vacancies in the compounds, confirmed by ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) analysis and density functional theoretical (DFT) calculations. Combination of oxygen vacancies and progressive doping of Ce onto BZO, BaZr1–xCexO3 (x = 0.00 – 0.04), creates additional energy levels stipulated by vacancy defects and Ce mixed valance states within the band gap of BZO thereby reducing its band gap. The photocatalytic efficacy of the compounds has been examined by photo-driven H2 generation concomitant with oxidation of a sacrificial donor. In this study, BaZr0.97Ce0.03O3 shows the highest efficiency (823 μmol h-1 g-1) with an apparent quantum yield (AQY) of 6% in photocatalytic H2 production among all five synthesized samples. The data obtained from the UV–Vis DRS, XPS, ESR analysis and DFT calculations, the synergistic effect of decreasing the band gap due to Ce doping and the presence of Ce (III)/Ce (IV) pairs along with oxygen vacancies and lattice distortions could be the reasons behind the enhanced photocatalytic efficacy of BaZr1–xCexO3 (x = 0.00 – 0.04) under UV–Visible light.
关键词： Photocatalytic hydrogen production,Cerium doping,Oxygen vacancies,BaZrO3,Hollow nanospheres
更新于2025-11-21 11:01:37
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dz2 Orbitals Mediated Bound Magnetic Polarons in Ferromagnetic Ce Doped BaTiO3 Nanoparticles and its Enriched Two Photon Absorption Cross Section
摘要： Enriched ferromagnetism and two photon absorption (TPA) cross section of perovskite BaTiO3 nanoparticles are indispensible for magnetic and optical data storage applications. In this work, the hydrothermally synthesized Ce doped BaTiO3 nanoparticles exhibit the maximum room temperature ferromagnetism (4.26×10-3 emu/g) at 4 mol% due to the increase of oxygen vacancies as evidenced by X-ray photoelectron, electron spin resonance spectroscopies and density functional theory (DFT) calculations. Hence, the oxygen vacancy constituted bound magnetic polaron (BMP) model has been invoked to explain the enhancement of ferromagnetism. BMP theoretical model indicates the increase of BMP magnetization (M0, 3.0 to 4.8×10-3 emu/g) and true spontaneous moment per BMP (meff, 4 to 9.88×10-4 emu) on Ce doping. DFT calculations show that BMPs mediate via Ti d orbitals leading to the ferromagnetism. Besides, it is understood that the magnetic moment induced by Ce at Ba site is higher than Ce at Ti site in the presence of oxygen vacancies. Open aperture Z-scan technique displays the highest TPA coefficient β (7.08×10-10 m/W) and TPA cross section σTPA (455×104 GM) at 4 mol% of Ce as a result of robust TPA induced excited state absorption. A large σTPA is attributed to the longer excited state lifetime τ (7.63 ns) of charge carriers created by oxygen vacancies and Ce ions which encounter several electronic transitions in the excited sub-states.
关键词： Ce doping,oxygen vacancies,bound magnetic polarons,two photon absorption,DFT calculations,Z-scan technique,BaTiO3 nanoparticles,ferromagnetism
更新于2025-11-19 16:56:35
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Synthesis, Morphology, Optical and Electrical Properties of Cu <sub/> 1? <i>x</i> </sub> Fe <sub/><i>x</i> </sub> O Nanopowder
摘要： The pure and Fe-doped CuO nanoparticles of the series Cu1?xFexO (x = 0, 0.027, 0.055, 0.097 and 0.125) were synthesized by a simple low temperature sol–gel method. Synthesized samples were characterized by a series of techniques including Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray electron spectroscopy (EDX), Diffuse Reflectance Spectroscopy (DRS), Fourier Transform Infrared Spectroscopy (FTIR), Hall Effect Set-up and Current–Voltage (I–V) characteristics. FESEM analysis shows formation of disc type structure increasing in grain size with Fe concentration in CuO. EDX confirmed the incorporation of iron in CuO. FTIR results of pure and Fe doped CuO samples have confirmed the formation of monoclinic CuO. The optical band gap estimated using Diffuse Reflectance Spectroscopy (DRS) shows the increment in the band gap values with Fe substitution. The Hall measurements show predominantly p-type conduction in all the samples and carrier densities decrease with increased Fe substitution. I–V characteristics of pure and Fe doped CuO nanoparticles show rectification behaviour of Schottky diodes.
关键词： Defect States,Hall Effect,Schottky Diode,Cation Vacancies,Fe-Substituted CuO
更新于2025-11-19 16:56:35
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Resistive switching behavior and mechanism in flexible TiO2@Cf memristor crossbars
摘要： Fiber-based memristors are expected to be one of the most ideal candidates to the future wearable nonvolatile devices. In this work, Carbon fibers coated with rutile TiO2 nanorods (TiO2 NRs) were prepared via hydrothermal method, which were denoted as TiO2@Cf. Flexible TiO2@Cf memristor crossbar was facilely assembled on a polyimide (PI) film. This device exhibited bi-directional threshold switching behavior and a maximum ON/OFF ratio of 105. In addition, the conductance of the memristors can be continuously adjusted by consecutive sweep cycles of bias voltages. The devices also exhibit excellent endurance over 1500 cycles with a negligible shift. The carriers transport and resistance switching of the TiO2@Cf memristor crossbar were explained by the Fowler-Nordheim tunneling model. The oxygen vacancies (OV) in TiO2 drifted to the interface of TiO2/Cf by an applied electric field, thereby reducing the depletion region and enhancing the current. This work provides a profound understanding of the resistive switching behavior and the related mechanism in flexible TiO2@Cf memristor crossbars, and paves a new way for potential applications for memristors in artificial synapses and flexible devices.
关键词： Artificial synapses,Oxygen vacancies,Memristor crossbars,Flexible devices,Carbon fibers
更新于2025-11-14 17:03:37
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Oxygen-vacancies-engaged efficient carrier utilization for the photocatalytic coupling reaction
摘要： Defects can greatly optimize the solar light harvesting capability and electronic structure of oxide materials. However, it remains challenging to achieve a defect engineering strategy under mild conditions. Meanwhile, the simultaneous exploitation of photogenerated holes (h+) and electrons (e?) to promote both photooxidation and photoreduction in a coupled system has rarely been reported. For the first time, we reveal an oxygen-vacancies-mediated photocatalytic strategy in which the electrons and holes are fully utilized for nitrobenzene reduction coupled with benzyl alcohol oxidation. The oxygen vacancies (OVs) generated in situ on the surface of TiO2 greatly extend light absorption into the visible region and promote the photogenerated electron transport for efficient photocatalysis. The experimental and theoretical results together indicate that chemisorption on the TiO2 surface decreases the oxidation potential of benzyl alcohol and causes an upward shift in its HOMO, which facilitates the oxidation reaction of benzyl alcohol to benzaldehyde. The in situ generated surface OVs also act as a bridge to enable the trapping and transferring of the photoinduced electrons to the nitrobenzene. This work provides a new perspective of utilizing the chemisorption between the reactant and catalyst to achieve a defect engineering strategy for synergetic photocatalysis.
关键词： Photocatalysis,Photoreduction,Surface complexation,Oxygen vacancies,Photooxidation
更新于2025-11-14 14:48:53
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Three-in-one oxygen vacancy: whole visible-spectrum absorption, efficient charge separation and surface site activation for robust CO2 photoreduction
摘要： Exploitation of efficient catalysts to realize solar-driven conversion of inert CO2 into useful fuels confronts big challenges owing to the poor photoabsorption, sluggish charge separation and inefficient surface reactive sites of photocatalysts. Herein, we report a facile and controllable in situ reduction strategy to create surface oxygen vacancies (OVs) on Aurivillius-phase Sr2Bi2Nb2TiO12 nanosheets. Sr2Bi2Nb2TiO12 nanosheets are for the first time prepared by a mineralizer-assisted soft-chemical method, and the introduction of OVs on the surface of Sr2Bi2Nb2TiO12 not only extends photo-response region, but also tremendously promotes separation of photo-induced charge carriers. Moreover, the adsorption and activation of CO2 molecules on the surface of the catalyst are largely enhanced. In the gas-solid reaction system without any co-catalysts or sacrificial agents, OVs-abundant Sr2Bi2Nb2TiO12 nanosheets show an outstanding CO2 photoreduction activity in producing CO with a rate of 17.11 μmol g?1 h?1, ~58 times higher than that of the bulk counterpart, surpassing most previously reported state-of-the-art photocatalysts. Our study provides a three-in-one integrated solution to advance the comprehensive performance of photocatalysts for solar-energy conversion and generation of renewable energy.
关键词： Sr2Bi2Nb2TiO12 nanosheets,charge separation,photocatalytic CO2 reduction,oxygen vacancies
更新于2025-09-23 15:23:52
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Surface Passivation of Perovskite Films via Iodide Salt Coatings for Enhanced Stability of Organic Lead Halide Perovskite Solar Cells
摘要： Organic–inorganic halide perovskite materials have emerged as attractive alternatives to conventional solar cells, but device stability remains a concern. Recent research has demonstrated that the formation of superoxide species under exposure of the perovskite to light and oxygen leads to the degradation of CH3NH3PbI3 perovskites. In particular, it has been revealed that iodide vacancies in the perovskite are key sites in facilitating superoxide formation from oxygen. This paper shows that passivation of CH3NH3PbI3 films with an iodide salt, namely phenylethylammonium iodide (PhEtNH3I) can significantly enhance film and device stability under light and oxygen stress, without compromising power conversion efficiency. These observations are consistent with the iodide salt treatment reducing iodide vacancies and therefore lowers the yield of superoxide formation and improves stability. The present study elucidates a pathway to the future design and optimization of perovskite solar cells with greater stability.
关键词： stability,perovskite solar cells,phenylethylammonium iodide,superoxide,iodide vacancies
更新于2025-09-23 15:23:52
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Photocatalytic Activity of ZnO Nanopowders: The role of production techniques in the formation of structural defects
摘要： The effect of the type of structural defect in zinc oxide on its photocatalytic properties was studied for phenol photodegradation under UV-irradiation. It was shown that the use of different types of precursors (zinc oxalate and zinc hydroxide) for the production of zinc oxide leads to the formation of a material with the same phase composition and equal energy of the forbidden band, but different photocatalytic activities. Simultaneously, the peculiarities of the luminescence and electron spin resonance spectra indicate the formation of different types of defects in the structure of the material, namely, oxygen vacancies (Vo) in the anionic and zinc vacancies (VZn) in the cationic sublattices of zinc oxide synthesised from the zinc oxalate and hydroxide, respectively. Also, the different characteristics of the luminescence decays reveal the different recombination paths for the free charge carriers in the systems synthesised from the different precursors. The different times of the luminescence decay also confirmed the different methods of recombination of free charge carriers in systems synthesised from different precursors. It was shown that the appearance of defects in the cationic sublattice leads to a decrease in the photocatalytic activity of the material relative to phenol degradation.
关键词： vacancies,luminescence.,Photocatalytic activity,structure defects,ZnO
更新于2025-09-23 15:23:52
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Enhanced photocatalytic activity of hydrogenated BiVO4 with rich surface-oxygen-vacancies for remarkable degradation of tetracycline hydrochloride
摘要： In this work, for the first time the hydrogenation treatment was employed to introduce oxygen vacancies on the surface of BiVO4 (BVO) particles, and the influence of hydrogenation on the morphological structure and photocatalytic activity of BVO was explored. Compared to the pristine BVO, a disordered amorphous layer was observed on the surface of the hydrogenated BVO (HBVO) sample. The disordered layer was due to the formation of surface oxygen vacancies in HBVO, as verified by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) spectra. Meanwhile, the band gap of HBVO was slightly narrowed accompanying with a higher optical absorption ability. The photocatalytic measurements demonstrated that under 30 min visible light (λ ≥ 420 nm) illumination the HBVO sample could photocatalytically degrade 98% of tetracycline hydrochloride (TCH), which was much higher than the pristine BVO (~52%), and the calculated pseudo-first-order degradation rate constant (k) of HBVO (~0.118 min?1) was about 5 times that of BVO, confirming that the hydrogenation treatment could significantly improve the photocatalytic activity of BVO. In addition, the photocatalytic mechanism of HBVO for enhanced photocatalytic TCH removal was also discussed. The present work demonstrates the feasibility of employing the hydrogenation treatment to develop highly efficient visible light BVO-based photocatalysts for photocatalytic removal of antibiotics, and also deepens the understanding of the correlation between surface oxygen vacancies and photocatalytic performance of semiconductor photocatalysts.
关键词： BiVO4,Photocatalytic activities,Tetracycline hydrochloride removal,Hydrogenation,Surface oxygen vacancies
更新于2025-09-23 15:23:52
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Efficient Conversion of CO <sub/>2</sub> to Methane Photocatalyzed by Conductive Black Titania
摘要： One of the major challenges encountered in CO2 utilization is the development of available and cost-efficient catalysts with sufficient activity, selectivity, and stability for the generation of useful methane. Here, conductive black titania, TiO2@x, is found to be efficient in photocatalyzing the reduction of CO2 to CH4. This unique material comprises a crystalline core–amorphous shell structure (TiO2@TiO2@x) with numerous surface oxygen vacancies, which facilitates the adsorption and chemical activation of CO2 molecules. Under full solar irradiation, the optimized 500-TiO2@x material with narrowed band gap and intermediate states below the conduction band tail exhibits a high space-time yield of CH4 of 14.3 mmol g@1 h@1, with 74 % selectivity and excellent photostability. The present findings can make a significant contribution, not only to develop the surface electron-modified black TiO2 catalyst to boost photocatalytic efficiency, but also to establish a really viable and convenient CH4 production process for CO2 conversion and renewable solar energy storage.
关键词： oxygen vacancies,photocatalysis,carbon dioxide chemistry,conductive black titania,methane generation
更新于2025-09-23 15:23:52