Xing Ding

Light-Switchable Oxygen Vacancies in Ultrafine Bi5O7Br Nanotubes for Boosting Solar-Driven Nitrogen Fixation in Pure Water

Solar-driven reduction of dinitrogen (N2 ) to ammonia (NH3 ) is severely hampered by the kinetically complex and energetically challenging multielectron reaction. Oxygen vacancies (OVs) with abundant localized electrons on the surface of bismuth oxybromide-based semiconductors are demonstrated to have the ability to capture and activate N2 , providing an alternative pathway to overcome such limitations. However, bismuth oxybromide materials are susceptible to photocorrosion, and the surface OVs are easily oxidized and therefore lose their activities. For realistic photocatalytic N2 fixation, fabricating and enhancing the stability of sustainable OVs on semiconductors is indispensable. This study shows the first synthesis of self-assembled 5 nm diameter Bi5 O7 Br nanotubes with strong nanotube structure, suitable absorption edge, and many exposed surface sites, which are favorable for furnishing sufficient visible light-induced OVs to realize excellent and stable photoreduction of atmospheric N2 into NH3 in pure water. The NH3 generation rate is as high as 1.38 mmol h-1 g-1 , accompanied by an apparent quantum efficiency over 2.3% at 420 nm. The results presented herein provide new insights into rational design and engineering for the creation of highly active catalysts with light-switchable OVs toward efficient, stable, and sustainable visible light N2 fixation in mild conditions.

Highly efficient visible light induced photocatalytic activity of a novel in situ synthesized conjugated microporous poly(benzothiadiazole)–C3N4 composite

In this study, a novel π-conjugated microporous poly(benzothiadiazole)–graphitic carbon nitride (BBT–C3N4) photocatalyst was synthesized through a facile in situ palladium-catalyzed Sonogashira–Hagihara cross-coupling polycondensation of 4,7-dibromobenzo[c][1,2,5]thiadiazole with 1,3,5-triethynylbenzene in the presence of evenly dispersed g-C3N4 using mixed DMF/TEA as solvent at 80 °C. Systematic characterization results revealed that BBT was equally dispersed on the surface of C3N4 with chemical bonds. The photocatalytic tests showed that this BBT–C3N4 composite exhibited enhanced photocatalytic removal of both sulfathiazole and Cr(VI) in comparison with the pure BBT and C3N4 as well as a mechanical mixture of BBT and C3N4, indicating that the oxidation and reduction abilities of BBT–C3N4 were simultaneously enhanced after composition under visible light irradiation. This was subsequently confirmed by radical detection, PL analysis and scavenger experiments as well. Holes and photoelectrons were demonstrated to be the main active species during the photocatalytic removal of sulfathiazole and Cr(VI), respectively. A possible photoelectron transfer mechanism for efficient photoinduced electron–hole separation of BBT–C3N4 composites is proposed based on all the results. This study provides new insight into the design of highly efficient visible light-driven photocatalysts with superior redox ability for wastewater treatment.

Surface plasmon resonance-induced visible-light photocatalytic performance of silver/silver molybdate composites

Abstract Novel silver/silver molybdate (Ag/Ag2MoO4) composites with surface plasmon resonance (SPR)-enhanced photocatalytic performance were successfully fabricated via a facile one-pot hydrothermal route with the presence of sodium dodecyl sulfate (SDS) in this study. The as prepared silver/silver molybdate (Ag/Ag2MoO4) composites were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible diffuse reflectance absorption spectroscopy (DRS) in order to investigate their crystal structure, morphology and optical property as well. The photocatalytic activities of the composites were subsequently evaluated by their ability to degrade rhodamine B (RhB) under visible-light irradiation. Varies of controlled experiments were then carefully operated to gain a deep insight into the assembling of Ag/Ag2MoO4 composites. It was found that preparation conditions such as pH, reaction time, and the amount of surfactant played important roles in the formation of composites with octahedral microstructures. And the composite obtained at 160 °C using 0.5 g of sodium dodecyl sulfate exhibited the highest photocatalytic performance under visible-light irradiation. Capture experiments were also conducted to clarify the function of different active species generated on the surface of Ag/Ag2MoO4 during the photocatalytic process, in which both holes and •OH radicals were found to play crucial role in photocatalytic removal of RhB under visible light irradiation. A possible photocatalytic mechanism of Ag/Ag2MoO4 was finally proposed on the basis of all the results to explain the higher photocatalytic activity of the octahedral Ag/Ag2MoO4 composites. It was inferred that the photoinduced “hot” electrons can quickly transfer from the Ag NPs to the conduction band of Ag2MoO4 and react with oxygen and H2O to generate a large quality of active radicals such as •OH and •O2− because of the SPR effects. Besides, this SPR effects of Ag nanoparticles deposited on the surface of Ag2MoO4 can not only dramatically amplify its light absorption, especially in the visible region, but also promote the separation of photoexcited electron-hole pairs and effectively decrease electron-hole recombination.

Oxygen Vacancy Boosted Photocatalytic Decomposition of Ciprofloxacin over Bi2MoO6: Oxygen Vacancy Engineering, Biotoxicity Evaluation and Mechanism Study

Herein, efficient visible light driven photocatalytic degradation of ciprofloxacin was realized over Bi2MoO6 with oxygen vacancies (OVs) which can be tunably introduced through a facile solvothermal method via the modulation of tetramethylethylenediamine (TMEDA). The optimal Bi2MoO6 with OVs possessed the highest CIP degradation rate of 1.799 mg min-1 m-1, about 8.4 times than that of the pristine Bi2MoO6. And more than half of CIP was mineralized in only 2 h. The biotoxicity of ciprofloxacin and its byproducts to E. coli K-12 and saccharomyces cerevisiae was thoroughly eliminated after 6 hs photocatalytic treatment. Characterization methods revealed the rich oxygen vacancies in Bi2MoO6 not only endowed it with broader visible light absorption and faster transfer of photogenerated carriers, but also provided abundant absorption sites of surface oxygen for efficient molecular oxygen activation. Correspondingly, plentiful active species were produced and participated in the photocatalytic process, thereby efficiently promoting the ciprofloxacin degradation. Based on the HPLC-MS analysis, a possible decomposition pathway of CIP was finally proposed with the first decomposition step of pipetazine ring oxidation and breakage. This work might open up new avenues for superior visible light driven photocatalysts design to deal with pharmaceutical compounds contamination via tunable OVs Engineering.

Simple fabrication of Fe3O4/C/g-C3N4 two-dimensional composite by hydrothermal carbonization approach with enhanced photocatalytic performance under visible light

The construction of a multifunctional two-dimensional (2D) composite photocatalyst is of great significance because such a composite can exhibit enhanced catalytic performance and improved practical usability in contrast to a single component catalyst. Herein, a ternary photocatalyst composed of g-C3N4, a carbon layer (C), and Fe3O4 nanoparticles was successfully synthesized by a facile one-pot hydrothermal carbonization (HTC) method from g-C3N4, glucose, and FeCl3. The resultant composite, Fe3O4/C/g-C3N4, had an ordered 2D heterostructure and exhibited enhanced visible-light-driven photocatalytic performances and good magnetic recyclability. The kobs for Cr(VI) photoreduction (or dimethoate photodegradation) over Fe3O4/C/g-C3N4 was 20.9-fold (or 2.1-fold) of that over g-C3N4. Comparative study of Fe3O4/C/g-C3N4, C/g-C3N4, and g-C3N4 on their optoelectronic properties revealed that this enhanced photocatalytic activity was mainly due to rapid photogenerated electron transport from the g-C3N4 component to carbon and/or Fe3O4, which effectively suppressed the recombination of photogenerated electrons and holes. In addition, the good surface adsorption capacity of the carbon component towards Cr(VI) also contributed to Cr(VI) photoreduction over Fe3O4/C/g-C3N4. Finally, a reasonable photocatalytic reaction mechanism of Fe3O4/C/g-C3N4 was proposed based on the results of trapping experiments. This study is not only limited to developing a high-performance g-C3N4 based photocatalyst, but also expected to provide a green, facile, and cost-efficient strategy to combine 2D materials with a carbonaceous layer and other functional components for a multifunctional system.