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Partially etched Bi2O2CO3 by metal chloride for enhanced reactive oxygen species generation: A tale of two strategies
摘要： Light-mediated reactive oxygen species generation with water and oxygen is generally regarded as a mild and efficient way for organic pollutants removal. However, it is highly difficult but desirable to construct a photochemical system with increased reactive oxygen species production. Herein, by using Bi2O2CO3 as a prototype, we devise a simple metal chloride-involved etching method to achieve better light absorption and charge carriers separation in a wide-band-gap semiconductor, thus giving rise to improved molecular oxygen activation. The improved photoinduced reactive oxygen species production is further verified by excellent photocatalytic degradation ability of RhB, TC and BPA under visible and ultraviolet light illumination. In addition, the metal chloride-induced strategies—heterojunction formation and cation doping—significantly affect the dynamics and transfer of carriers, which are advantageous to manipulate one-/two-electron pathway for producing reactive oxygen species.
关键词： Metal chloride,Photocatalytic,Bi2O2CO3,Reactive oxygen species,Heterojunction
更新于2025-09-23 15:23:52
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Facet effect on the photoelectrochemical performance of a WO3/BiVO4 heterojunction photoanode
摘要： Different WO3 facets have different surface energies and electronic structures, and exhibit different water oxidation abilities and photocatalytic performance as a result. Because of the material’s limited photoresponse region, loading a narrow bandgap material on WO3 is a generally known method for improving photo-harvesting. In this paper, we have synthesized WO3 films with different crystal facet ratios. After loading BiVO4 on these WO3 films, we measured the photoelectrochemical (PEC) performance to investigate the effects of WO3 facet choice on the heterojunction film electrode’s performance. We found that a high-intensity ratio of the (002) WO3 facet in X-ray diffraction (XRD) leads to a more negative onset potential and higher photocurrents in a lower potential region. The ultraviolet photoelectron spectra show a lower work function for the 002-dominant WO3 film compared to other WO3 films, which may result in a higher quasi-fermi level for the heterojunction electrode. Based on the XRD results, the high-intensity ratio of the (002) WO3 facet preferentially exposes the (020) BiVO4 facet, which may be a reason for the better charge extraction observed at low applied potential and high faradic efficiency on PEC water splitting. Together, this results in a high hole injection efficiency for 002-dominant WO3/BiVO4 films compared with WO3/BiVO4 films favoring other WO3 facet ratios.
关键词： BiVO4,WO3,Photoelectrochemical performance,Facet effect,Heterojunction
更新于2025-09-23 15:23:52
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A novel Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst: Study on the excellent photocatalytic performance and photocatalytic mechanism
摘要： A novel three-dimensional microspheres mediator-free Z-scheme Ag3VO4/BiVO4 heterojunction photocatalyst was successfully obtained for the first time. The photocatalytic performance of the as-prepared photocatalyst was systematically examined via the photocatalytic reduction of Cr6+ and oxidation of Bisphenol S under visible-light irradiation. Among these samples, 0.24-Ag3VO4/BiVO4 exhibits the highest photocatalytic performances, the photocatalytic reduction and oxidation efficiency of 74.9 and 94.8 %, respectively, can be achieved. The enhanced photocatalytic performance is attributed to the build-in electric field assisted charge transfer between the Ag3VO4 and BiVO4, and the increasing lifetime of the charge carrier confirmed by the results of time-resolved fluorescence spectra and photoelectrochemical measures. Moreover, based on the results of free radical scavenging activity test, and EPR experiments, it has been verified that the Ag3VO4/BiVO4 heterostructures follow a typical Z-scheme charge transfer mechanism rather than conventional type-II heterojunction charge transfer mechanism. Furthermore, the theoretical understanding of the underlying mechanism was also supported, while the energy band structure, and Fermi level were systematically calculated using the density functional theory approach. The results show that a built-in electric field directed from Ag3VO4 to BiVO4 surface was established as an equalized Fermi level was reached, which benefits the separation of photogenerated charge carriers in the way of a Z-scheme charge transfer mechanism. The strategy to form the three-dimensional microspheres Z-scheme heterojunction photocatalyst may offer new insight into the Z-scheme charge transfer mechanism for applications in the field of solar energy conversion.
关键词： Bismuth Vanadate,Z-scheme heterojunction photocatalyst,photocatalytic reduction and oxidation.
更新于2025-09-23 15:23:52
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The current-voltage characteristics of the ferroelectric p-YMnO3 thin film/bulk p-Si heterojunction over a broad measurement temperature range
摘要： The reverse and forward bias I-V characteristics of the Al/p-YMO/p-Si/Al heterojunction were measured at room temperature (RT) and over temperature range, from 50 to 320 K, and the I-V curves showed Schottky diode-like characteristics. The ideality factor and barrier height values were calculated as 0.81 and 2.62 from the forward bias I-V curve at room temperature (300 K), respectively. The YMO powder was prepared via solid state reaction technique. YMO thin films were grown on front surface of p-Si substrate by radio frequency (rf) magnetron sputtering using a polycrystalline YMO single target. The YMO thin film thickness on Si substrate was measured as ~70 nm via Dektak XT surface profilometer. The XRD, SEM, UV-Vis and XPS measurements of the YMO thin film were also performed. The bandgap energy of YMnO3 thin films was determined as 2.10 eV by UV-vis. The temperature-dependent reverse and forward bias I-V curves were evaluated in terms of thermionic emission (TE), Schottky emission, Fowler-Nordheim (F-N) tunneling and space charge-limited current (SCLC) current theories. Furthermore, it has been seen that the forward bias conduction in the junction at each temperature obeys F-N tunneling because of the linearity in the ln (I/V2) versus V-1 curves.
关键词： Polycrystalline,Heterojunction,Ferroelectric,Al/p-YMO/p-Si/Al,Schottky barrier,YMnO3,Temperature dependent current characteristics
更新于2025-09-23 15:23:52
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Interfacial engineering of Fe2O3@BOC heterojunction for efficient detoxification of toxic metal and dye under visible light illumination
摘要： Recent developments of small band gap semiconductor coupled bismuth carbonate (BOC) heterojunction are advantageous for photocatalysis application because of their improved solar harvesting ability and enhanced charge-carrier collection. In this work, we have developed iron (III) oxide decorated bismuth carbonate (Fe2O3@BOC) heterojunction via a simple two-step process. The developed heterojunction exhibits excellent photocatalytic activity towards reduction of carcinogenic and mutagenic Cr(VI) to nontoxic Cr(III) and degradation of toxic dye [methylene blue (MB)] under visible light illumination. Further investigation revealed that the loading of Fe2O3 nanoparticles had an impact on efficient charge carrier collection at the interface of Fe2O3@BOC heterojunctions. The unprecedented photocatalytic activity for Fe2O3@BOC1 heterojunction at room temperature could be attributed due to the enhancement in light absorption ability and suppression of electron–hole pair recombination at the heterojunction interface. In addition, reduction in efficacy of the heterojunction with increase in loading of Fe2O3 nanoparticles on BOC surface further confirms the role of interface on the modulation of photocatalytic activity. The role of photogenerated electrons and reactive oxygen species involved during photocatalytic reduction of Cr(VI) and degradation of MB was studied in detail. Moreover, recyclability experiment demonstrates that the developed photocatalyst can be reused without decay in performance. Finally, development of inexpensive prototype reactor is demonstrated towards reduction of Cr(VI) and degradation of MB under continuous flow operation. Thus, good efficacy of the developed reactor for cleaning of toxic pollutants in water makes the heterojunction (Fe2O3@BOC1) a promising photocatalyst for water purification in near future.
关键词： photocatalytic activity,charge separation,Heterojunction,toxic pollutants,visible light
更新于2025-09-23 15:23:52
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Ordered mesoporous WO3/ZnO nanocomposites with isotype heterojunctions for sensitive detection of NO2
摘要： Ordered mesoporous WO3 nanocrystals have been successfully synthesized by a hydrothermal method using mesoporous silica of KIT-6 as a template and phosphotungstic acid as a precursor of WO3. The structure, morphology, and specific surface of WO3 nanocrystals were systematically characterized by XRD, SAXS, HR-TEM, and BET. To improve the sensing properties of WO3 to NO2, a series of different ZnO amounts were loaded on the mesoporous WO3 to construct nanocomposites with n–n heterojunction for the fabrication of NO2 sensors. The gas-sensing behaviors show that the sensor based on WO3/5 wt% ZnO composite to 1 ppm of NO2 not only exhibits the high response, but also has good selectivity and stability at operating temperature of 150 oC, which can be contributed to the large specific surface and porous channels provided by mesoporous structures, and the formation of n–n heterojunctions at interface between both oxides.
关键词： NO2 sensor.,ZnO,Mesoporous WO3,n–n isotype heterojunction
更新于2025-09-23 15:23:52
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H2 production by the water splitting reaction using photocatalysts derived from calcined ZnAl LDH
摘要： Photocatalysts based on calcined ZnAl layered double hydroxides were obtained by coprecipitation and the subsequent thermal treatments at different temperatures. The calcined materials were characterized and its photocatalytic behavior was evaluated in the water splitting reaction in presence of UV irradiation. According to the XRD analysis, there was detected the presence of Zn as hexagonal ZnO in all the samples, as well as Al forming ZnAl2O4 and Zn6Al2O9, depending on the temperature of calcination employed. H2 yield was higher as the annealing temperature was increased due to the formation of the heterojunctions of ZnO with the Zn6Al2O9 and ZnAl2O4 oxides, reaching the maximum value in the sample annealed at 600 °C. Some decay in the activity was observed in the sample calcined at 700 °C, probably due to the higher recombination rate of the photo-generated charge carriers in that heterojunction in comparison with that obtained at 600 °C.
关键词： Hydrogen,Calcined LDH,ZnAl mixed oxides,Photocatalyst,Heterojunction,Water splitting
更新于2025-09-23 15:23:52
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Effects of Ge substrate on the structural and optical conductivity parameters of Bi2O3 thin films
摘要： In this article the structural, optical and dielectric properties of a 200 nm thick Bi2O3 thin films which are deposited onto amorphous germanium substrate are reported. Both of the Ge and Bi2O3 thin films are prepared by the thermal evaporation technique under vacuum pressure of 10^-5 mbar. Bi2O3 thin films are found to prefer the monoclinic nature of structure with larger values of microstrain, dislocation density, stacking faults and smaller grain sizes upon replacement of the glass substrate by germanium. Optically, significant redshift in the energy band gap is observed when the films are grown onto Ge. The Ge/Bi2O3 heterojunctions exhibit a conduction and valence band offsets of value of 0.81 and 1.38 eV, respectively. In addition to the enhancement in the dielectric constant near the IR region, the Drude-Lorentz modeling of the Ge/Bi2O3 heterojunctions has shown remarkable effect of the Ge substrate on the optical conductivity parameters of Bi2O3. Particularly, the drift mobility increased by about one order of magnitude, the free hole density decreased by ~24 times and the plasmon frequency ranges extended from 5.21 to 11.0 GHz to 2.59–12.80 GHz when germanium substrate is used. The optical features of the heterojunction nominate it for visible light communication technology.
关键词： Ge/Bi2O3,Band offsets,X-ray,Heterojunction,Plasmon,Dielectric
更新于2025-09-23 15:23:52
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Construction of Pt-decorated g-C3N4/Bi2WO6 Z-scheme composite with superior solar photocatalytic activity toward rhodamine B degradation
摘要： Highly efficient visible-light-driven Pt-decorated g-C3N4/Bi2WO6 hybrid photocatalysts were successfully prepared via a photodeposition method. The microstructures and optical properties of the prepared samples were characterized by transient photocurrent experiments, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV-vis diffused reflectance spectra (DRS), photoluminescence (PL), electron spin resonance (ESR) spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. FESEM and TEM images show that metallic Pt particles disperse on the surface of g-C3N4/Bi2WO6 hybrid. Pt-decorated g-C3N4/Bi2WO6 compsites exhibited excellent DRS attribute to the surface plasmonic resonance (SPR) of Pt particles and g-C3N4/Bi2WO6. The PL results verified that the suitable band potential of g-C3N4 and Bi2WO6 for construction of Z-type photocatalytic system. In the photocatalytic experiment, results showed that Pt(1%)-g-C3N4/Bi2WO6 photocatalysts displayed higher photocatalytic activity than either pure g-C3N4 or Bi2WO6 for the degradation of Rhodamine B (RhB). Additionally, the free-radical trapping experiments and ESR disclose that the hole (h+), superoxide radical (·O2-) and hydroxyl radical (·OH) acted as reactive species. Based on above, a possible plasmonic Z-scheme mechanism for organics degradation over Pt-decorated g-C3N4/Bi2WO6 was proposed.
关键词： g-C3N4/Bi2WO6,Visible light irradiation,Z-scheme heterojunction,Pt-decorated
更新于2025-09-23 15:23:52
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A novel silicon heterojunction IBC process flow using partial etching of doped a-Si:H to switch from hole contact to electron contact <i>in situ</i> with efficiencies close to 23%
摘要： We present a novel process sequence to simplify the rear‐side patterning of the silicon heterojunction interdigitated back contact (HJ IBC) cells. In this approach, interdigitated strips of a‐Si:H (i/p+) hole contact and a‐Si:H (i/n+) electron contact are achieved by partially etching a blanket a‐Si:H (i/p+) stack through an SiOx hard mask to remove only the p+ a‐Si:H layer and replace it with an n+ a‐Si:H layer, thereby switching from a hole contact to an electron contact in situ, without having to remove the entire passivation. This eliminates the ex situ wet clean after dry etching and also prevents re‐exposure of the crystalline silicon surface during rear‐side processing. Using a well‐controlled process, high‐quality passivation is maintained throughout the rear‐side process sequence leading to high open‐circuit voltages (VOC). A slightly higher contact resistance at the electron contact leads to a slightly higher fill factor (FF) loss due to series resistance for cells from the partial etch route, but the FF loss due to J02‐type recombination is lower, compared with reference cells. As a result, the best cell from the partial etch route has an efficiency of 22.9% and a VOC of 729 mV, nearly identical to the best reference cell, demonstrating that the developed partial etch process can be successfully implemented to achieve cell performance comparable with reference, but with a simpler, cheaper, and faster process sequence.
关键词： interdigitated back contact (IBC),H2 plasma,amorphous silicon,heterojunction,dry etch,process simplification,NF3/Ar plasma,in situ processing
更新于2025-09-23 15:23:52