Introducing oxygen vacancies in TiO_(2) lattice through trivalent iron to enhance the photocatalytic removal of indoor NO

The synthesis of oxygen vacancies(OVs)-modified TiO_(2)under mild conditions is attractive.In this work,OVs were easily introduced in TiO_(2)lattice during the hydrothermal doping process of trivalent iron ions.Theoretical calculations based on a novel charge-compensation structure model were employed with experimental methods to reveal the intrinsic photocatalytic mechanism of Fe-doped TiO_(2)(Fe-TiO_(2)).The OVs formation energy in Fe-TiO_(2)(1.12 eV)was only 23.6%of that in TiO_(2)(4.74 eV),explaining why Fe^(3+)doping could introduce OVs in the TiO_(2)lattice.The calculation results also indicated that impurity states introduced by Fe^(3+)and OVs enhanced the light absorption activity of TiO_(2).Additionally,charge carrier transport was investigated through the carrier lifetime and relative mass.The carrier lifetime of Fe-TiO_(2)(4.00,4.10,and 3.34 ns for 1at%,2at%,and 3at%doping contents,respectively)was longer than that of undoped TiO_(2)(3.22 ns),indicating that Fe^(3+) and OVs could promote charge carrier separation,which can be attributed to the larger relative effective mass of electrons and holes.Herein,Fe-TiO_(2)has higher photocatalytic indoor NO removal activity compared with other photocatalysts because it has strong light absorption activity and high carrier separation efficiency.

Enhanced photocatalytic NO removal and toxic NO2 production inhibition over ZIF‐8‐derived ZnO nanoparticles with controllable amount of oxygen vacancies

The controlled introduction of oxygen vacancies(OVs)in photocatalysts has been demonstrated to be an efficient approach for improving the separation of photogenerated charge carriers,and thus,for enhancing the photocatalytic performance of photocatalysts.In this study,a two‐step calcination method where ZIF‐8 was used as the precursor was explored for the synthesis of ZIF‐8‐derived ZnO nanoparticles with gradient distribution of OVs.Electron paramagnetic resonance measurements indicated that the concentration of OVs in the samples depended on the temperature treatment process.Ultraviolet–visible spectra supported that the two‐step calcined samples presented excellent light‐harvesting ability in the ultraviolet‐to‐visible light range.Moreover,it was determined that the two‐step calcined samples presented superior photocatalytic performance for the removal of NO,and inhibited the generation of NO2.These properties could be attributed to the contribution of the OVs present in the two‐step calcined samples to their photocatalytic performance.The electrons confined by the OVs could be transferred to O2 to generate superoxide radicals,which could oxidize NO to the final product,nitrate.In particular,the NO removal efficiency of Z 350‐400(which was a sample first calcined at 350℃ for 2 h,then at 400℃ for 1 h)was 1.5 and 4.6 times higher than that of Z 400(which was one‐step directly calcined at 400℃)and commercial ZnO,respectively.These findings suggested that OV‐containing metal oxides that derived from metal‐organic framework materials hold great promise as highly efficient photocatalysts for the removal of NO.

REMOVAL OF ORGANIC POLLUTANTS USING TITANIUM DIOXIDE MEDIATED PHOTOCATALYTIC OXIDATION

A simple and effective method of removing polluted organics in water is reported here.Titanium dioxide is a catalyst in photo-oxidation of monocrotophos.The mechanism of photocatalytic oxidation and the kinetics of the reaction were studied. This same principle also leads to the construction of instrument of PTR-FIA analysis for monitoring organic phosphorus and phosphate in water.

Earth-Abundant CaCO_(3)-Based Photocatalyst for Enhanced ROS Production,Toxic By-Product Suppression,and Efficient NO Removal

Photoinduced reactive oxygen species(ROS)-based pollutant removal is one of the ideal solutions to achieve the conversion of solar energy into chemical energy and thus to address environmental pollution.Here,earthabundant CaCO_(3)-decorated g-C_(3)N_(4)(g-C_(3)N_(4)labeled as CN,CaCO_(3)-decorated g-C_(3)N_(4)sample labeled as CN-CCO)has been constructed by a facile thermal polymerization method for safe and efficient photocatalytic NO removal.The decorated CaCO_(3)as“transit hub”extends theπbonds of CN to deviate from the planes and steers the random charge carriers,which thus provides extra active sites and expedites spatial charge separation to facilitate adsorption/activation of reactants and promote formation of ROS participating in the removal of pollutant.Furthermore,boosted generation of ROS regulates the photocatalytic NO oxidation pathway and thus increases the selectivity of products.NO prefers to be directly oxidized into final product(nitrate)rather than toxic intermediates(NO_(2)),which is well demonstrated by theoretically simulated ROS-based reaction pathways and experimental characterization.The present work promotes the degradation of pollutant and simultaneously suppresses the formation of toxic by-product,which paves the way for ROS-based pollutant removal.

Enhanced plasmonic photocatalysis by SiO_2@Bi microspheres with hot-electron transportation channels via Bi–O–Si linkages

The semimetal Bi has received increasing interest as an alternative to noble metals for use in plasmonic photocatalysis. To enhance the photocatalytic efficiency of metallic Bi, Bi microspheres modified by SiO2 nanoparticles were fabricated by a facile method. Bi-O-Si bonds were formed between Bi and SiO2, and acted as a transportation channel for hot electrons. The SiO2@Bi microspheres exhibited an enhanced plasmon-mediated photocatalytic activity for the removal of NO in air under 280 nm light irradiation, as a result of the enlarged specific surface areas and the promotion of electron transfer via the Bi-O-Si bonds. The reaction mechanism of photocatalytic oxidation of NO by SiO2@Bi was revealed with electron spin resonance and in situ diffuse reflectance infrared Fourier transform spectroscopy experiments, and involved the chain reaction NO -> NO2 -> NO3- with center dot OH and center dot O-2(-) radicals as the main reactive species. The present work could provide new insights into the in-depth mechanistic understanding of Bi plasmonic photocatalysis and the design of high-performance Bi-based photocatalysts. (C) 2017, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Synthesis of crystalline carbon nitride with enhanced photocatalytic NO removal performance:An experimental and DFT theoretical study

The pristine carbon nitride derived from the thermally-induced polymerization of nitrogen-containing precursors(e.g.cyanamide,dicyanamide,melamine and urea)displays low crystallinity because of the predominantly kinetic hindrance.Herein,we reported a modified molten-salts method to fabricate the crystalline carbon nitride under ambient pressure,which is expected to the large-scale production of crystalline carbon nitride.The obtained crystalline carbon nitride displayed about 3.0 times higher photocatalytic NO removal performance than that of pristine carbon nitride under visible light irradiation(λ<400 nm).Detailed experimental characterization and theoretical calculation revealed the crucial roles of crystallinity in crystalline carbon nitride for the enhanced photocatalytic NO removal performance.This research provided deep insights into the crystallinity of carbon nitride for the enhanced photocatalytic performance.

Self-doped Br in Bi_(5)O_(7)Br ultrathin nanotubes:Efficient photocatalytic NO purification and mechanism investigation

Bismuth-rich Bi_(5)O_(7)Br is a promising photocatalyst for pollutant removal owing to its stability and appropriate band structure in comparison with bismuth oxybromide.However,bulk-phase Bi_(5)O_(7)Br suffers from poor light absorption and high charge recombination rates resulting in poor activity.Elemental doping is a powerful strategy to enhance photocatalytic activity.In this study,we prepared a series of Br autodoped ultrathin Bi_(5)O_(7)Br nanotubes and explored the effect of Br doping on photocatalytic NO removal.The optimal doping content was determined via a photocatalytic NO removal experiment,which revealed the optimal ratio of Bi and Br was approximately 3:1.In situ diffuse reflectance infrared Fourier transform spectroscopy(In situ DRIFT)and density functional theory(DFT)studies revealed that NO removal mechanism catalyzed by Br doped Bi_(5)O_(7)Br.Our work presents a new strategy for the enhancement of photocatalytic pollutant degradation by bismuth oxyhalide photocatalysts.

Hierarchical BiOBr microspheres with oxygen vacancies synthesized via reactable ionic liquids for dyes removal

Hierarchical BiOBr microspheres with oxygen vacancies, which can be used for the dyes removal, have been synthesized successfully in the presence of different kinds of ionic liquids. It was revealed that BiOBr prepared by the ionic liquids with short chain length exhibited higher photocatalytic activity in the degradation of methyl orange （MO） under visible light. The experimental results showed that the phenomenon of the photocatalytic degradation of MO can be explained by the photoluminescence spectra.

Nb_2O_5 nanowires in-situ grown on carbon fiber: A high-efficiency material for the photocatalytic reduction of Cr(Ⅵ)

Niobium oxide nanowire-deposited carbon fiber（CF） samples were prepared using a hydrothermal method with amorphous Nb2O5·nH2O as precursor. The physical properties of the samples were characterized by means of numerous techniques, including X-ray diffraction（XRD）, energy-dispersive spectroscopy（EDS）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, selected-area electron diffraction（SAED）, UV–visible spectroscopy（UV–vis）, N2 adsorption–desorption, Fourier transform infrared spectroscopy（FT-IR）, and X-ray photoelectron spectroscopy. The efficiency for the removal of Cr（VI） was determined.Parameters such as pH value and initial Cr（VI） concentration could influence the Cr（VI） removal efficiency or adsorption capacity of the Nb2O5/carbon fiber sample obtained after hydrothermal treatment at 160°C for 14 hr. The maximal Cr（VI） adsorption capacity of the Nb2O5 nanowire/CF sample was 115 mg/g. This Nb2O5/CF sample also showed excellent photocatalytic activity and stability for the reduction of Cr（Ⅵ） under UV-light irradiation： the Cr（VI） removal efficiency reached 99.9% after UV-light irradiation for 1 hr and there was no significant decrease in photocatalytic performance after the use of the sample for 10 repeated cycles. Such excellent Cr（VI） adsorption capacity and photocatalytic performance was related to its high surface area,abundant surface hydroxyl groups, and good UV-light absorption ability.

InP quantum dots on g-C_(3)N_(4) nanosheets to promote molecular oxygen activation under visible light

Largely limited by the high dissociation energy of the O—O bond,the photocatalytic molecular oxygen activation is highly challenged,which re strains the application of photocatalytic oxidation technology for atmospheric pollutants removal.Herein,we design and fabricate the InP QDs/g-C_(3)N_(4) compounds.The introduction of InP QDs promotes the charge transfer within the interface resulting in the effective separation of photo-generated carriers.Furthermore,InP QDs greatly facilitates the activation of molecular oxygen and promote the formation of O_(2)·under visible-light illuminatio n.These conclusions are identified by experimental and calculation results.Hence,NO can be combined with the O_(2)·to form O—O—N—O intermediate to direct conversion into NO_(3).As a result,the NO removal ratio of g-C_(3)N_(4) has a one fold increase after InP QDs loaded and the generation of NO_(2) is effectively inhibited.This wo rk may provide a strategy to design highly efficient materials for molecular oxygen activation.