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•1D/2D CdS nanorod@Ti3C2 MXene (CdS@Ti3C2) composite was synthesized.•CdS@Ti3C2 composite exhibits photocatalytic H2 production rate of 63.5276 μmol h−1.•CdS@Ti3C2 composite exhibits ...photocatalytic N2 fixation rate of 293.06 μmol L−1 h−1.•The conductive Ti3C2 MXene can significantly promote electron transfer.•The accordion-like multilayers of CdS@Ti3C2 composite can provide more active sites.
In this study, the unique 1D/2D CdS nanorod@Ti3C2 MXene (CdS@Ti3C2) composites photocatalysts are prepared by a hydrothermal strategy. The suitable band structure and superior electronic reduction capability of CdS in CdS@Ti3C2 composites are achieved, efficiently prolong the light absorption range and enhance photocatalytic performance of CdS. Moreover, Ti3C2 MXene NSs with good electronic transfer capability can prevent photoinduced carrier recombination, and the accordion-like multilayer can provide more reactive sites. The best sample of CdS@Ti3C2 with 15 mg Ti3C2 MXene adding amount exhibits super good photocatalytic H2 evolution rate (63.53 μmol h−1), and photocatalytic nitrogen fixation rate of 293.06 μmol L−1 h−1. The corresponding apparent quantum efficiencies (AQE) are 2.28% and 7.88%, respectively, higher than those of pure CdS NRs and CdS@Pt (0.1 wt%). Besides, CdS@Ti3C2-15 composite shows good long-term stability under simulated sunlight irradiation.
Abstract
Transient behavior of a magnetorheological brake excited by step currents under compression-shear mode has been experimentally studied. The results show that the amplitude of the applied ...current had little effect on the rising time of transient torque, while the rising time was significantly affected by the rotational speed, the compressive speed and the compressive strain position. The falling time of transient torque was independent of the amplitude of the applied current, the compressive speed and the compressive strain position, and it was affected by the rotational speed. The falling time of the transient torque was much shorter than the rising time by a step current. The transient process of MR brake applied as a step current was different from a stable process pre-applied at constant current in different particle chain structure forming processes. In addition, the compressive processes applied in one step current and randomly on/off current were compared and experimentally verified: the particle chains in two processes both experienced the same evolutionary of transient torque. The results achieved in this study should be properly considered in the design and control of magnetorheological brake under compression-shear mode.
This work provides a mechanistic insight into the effects of different type of N-doped carbon-supported catalysts on the synthesis of VAc by the acetylene method. The introduction of N-doping can ...enhance the adsorption of acetylene and acetic acid molecules onto the catalyst supports. The N6–3 surface which with three pyridinic-N shows the most adsorption stability for both acetylene and acetic acid molecules, and facilitates the synthesis of VAc efficiently. While the N6 surface which with the pyridinic-N is obstructive to the VAc formation.
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•The N-doping enhances the adsorption of acetylene and acetic acid molecules.•The activation barrier could be effectively lowered by a concerted TS1.•The N6–3 surface facilitates the VAc synthesis by acetylene method efficiently.
TiO2 has been generally studied for photocatalytic sterilization, but its antibacterial activities are limited. Herein, TiO2 nanospheres with rutile/anatase heterophase junctions are prepared by a ...wet chemical/annealing method. The large BET surface area and pore size are beneficial for the absorption of bacteria. The rutile/anatase heterojunctions narrow the bandgap, which enhances light absorption. The rutile/anatase heterojunctions also efficiently promote the photogenerated carriers’ separation, finally producing a high yield of radical oxygen species, such as •O2− and •OH, to sterilize bacteria. As a consequence, the obtained TiO2 nanospheres with rutile/anatase heterojunctions present an improved antibacterial performance against E. coli (98%) within 3 h of simulated solar light irradiation, exceeding that of TiO2 nanospheres without annealing (amorphous) and TiO2 nanospheres annealing at 350 and 550 °C (pure anatase). Furthermore, we design a photocatalytic antibacterial spray to protect the file paper. Our study reveals that the TiO2 nanospheres with rutile/anatase heterojunctions are a potential candidate for maintaining the durability of paper in the process of archival protection.
In this research work, the 1T phase WS2 NSs decorated Bi5O7Br NSs (named 1T-WS2@Bi5O7Br composites) have narrower band gap, more effective carrier transport efficiency and better light absorption ...ability. After testing, 1T-WS2@Bi5O7Br-5 composites present the best photocatalytic nitrogen fixation performance (8.43 mmol L−1 h−1 g−1) and excellent stability. The probable photocatalytic mechanism of 1T-WS2@Bi5O7Br composites is proposed.
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Recently, widespread attention has been devoted to the typical layered BiOCl or BiOBr because of the suitable nanostructure and band structure. However, owing to the fast carrier recombination, the photocatalytic performance of BiOX materials is not so satisfactory. Loading 1T phase WS2 nanosheets (NSs) onto Bi5O7Br NSs can improve the photocatalytic N2 fixation activity. Among these, the obtained 1T-WS2@Bi5O7Br composites with optimum 5% 1T-WS2 NSs display a significantly improved photocatalytic N2 fixation rate (8.43mmolL−1h−1g−1), 2.51 times higher than pure Bi5O7Br (3.36mmolL−1h−1g−1). And the outstanding stability of 1T-WS2@Bi5O7Br-5 composites is also achieved. Exactly, the photoexcited electrons from Bi5O7Br NSs are quickly transferred to conductive 1T phase WS2 as electron acceptors, which can promote the separation of carriers. In addition, 1T-WS2 NSs can provide abundant active sites on the basal and edge planes, which can promote the efficiency of photocatalytic N2 fixation. This work offers a novel solution to improve the photocatalytic performance of Bi5O7Br NSs.
Our previous experimental report showed a switching behavior from ethylene polymerization to nonselective oligomerization by a novel triphenylsiloxy complex of chromium(II) ...(Ph3SiO)Cr·(THF)2(μ-OSiPh3)2 (1) together with methylaluminoxane (MAO) as a cocatalyst. In this work, combined experimental and computational studies were carried out to shed some light on the nature of the active species and their fascinating switching mechanism. The experimental results and DFT calculations suggested that (i) the chain propagation and chain transfer processes proceed via a Cossee–Arlman mechanism and β-hydrogen transfer to the chromium center, respectively; (ii) the trivalent cationic model (Ph3SiO)CrIIIMe+ and (η6-toluene)CrIIIMe2+, which could be generated by a disproportionation reaction, are the most plausible active species for ethylene polymerization, and the divalent cationic model (η6-toluene)CrIIMe+ might be responsible for ethylene nonselective oligomerization. A switching mechanism from ethylene polymerization to nonselective oligomerization in the 1/MAO catalyst system was proposed on the basis of DFT calculations. These results may have useful implications for studying active species and the mechanism of transition-metal-catalyzed olefin polymerization and oligomerization.
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The graphitic carbon nitride (g-C3N4) hollow nanotubes synthesized via a simple freeze-drying method are used for constructing Two-dimensional (2D)-one-dimensional (1D) molybdenum ...sulfide (MoS2) nanoflake/g-C3N4 hollow nanotube (MoS2/g-C3N4 nanotube) photocatalysts. The MoS2/g-C3N4 nanotube composite with 15 wt% MoS2 shows the highest hydrogen (H2) production rate (1124 μmol·h−1·g−1), much higher than bulk g-C3N4 (64 μmol·h−1·g−1) and g-C3N4 nanotubes (189 μmol·h−1·g−1). The excellent photocatalytic activity of MoS2/g-C3N4 nanotube composites can be ascribed to more exposed active edges of 2D-1D structure, multiple light reflection/scattering channels of 2D nanoflake/1D hollow nanotube composite structure and better carrier transfer and separation by heterojunction interface.
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•The Au NRs/g-C3N4 heterostructure with Au nanorods on the surface of g-C3N4 is synthesized successfully.•The Au NRs/g-C3N4 heterostructure exhibits the best photocatalytic activity ...under visible and NIR light irradiation.•Au nanorods are excited in visible and NIR regions to serve as plasmonic photosensitizers.•Au nanorods offer hot electrons to g-C3N4 and reduce the recombination of excited charges.
Recently, broad spectrum (visible and near-infrared (NIR)) light utilization has aroused widespread attention in the research of photocatalysis. While g-C3N4, highly stable, cheap and easily synthesized, shows H2 evolution activity under visible light irradiation, it doesn’t perform under NIR light irradiation. Here we report an Au nanorods (NRs)/g-C3N4 heterostructure with Au nanorods on g-C3N4’s surface. The most exciting feature of designed Au NRs/g-C3N4 heterostructures is that Au nanorods themselves are excited by visible and NIR light, which produce hot electrons and inject into g-C3N4. The photocatalytic H2 evolution rate of Au NRs/g-C3N4 heterostructures (350.6 μmol g−1 h−1) is nearly 4 times higher than that of g-C3N4 with Pt as cocatalyst (68.9 μmol g−1 h−1) under visible light illumination. The improved photocatalytic activity is ascribed to the increasing visible light-absorbing capacity of transverse surface plasmon resonance (TSPR) of Au nanorods and improved charge separation of Au NRs/g-C3N4 heterostructure. Even more important, Au NRs/g-C3N4 heterostructures achieve NIR photocatalytic H2 evolution performance (63.1 μmol g−1 h−1), owing to the longitudinal SPR (LSPR) effect of Au nanorods induced NIR light harvesting ability.
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Finding an efficient and environment-friendly photocatalyst is significant for photocatalysis. In this research, a simple calcination with urea and salicylic acid (SA) is created for ...constructing a SA-modified graphite carbon nitride (g-C3N4-SA) photocatalyst. Compared to pure g-C3N4, g-C3N4-SA presents broadened light absorption, due to n → π* transition at nitrogen atoms. Interestingly, SA modification can strongly affect chemical and physical properties of g-C3N4, including increasing Brunauer-Emmett-Teller (BET) specific area, forming porous structure, improving optical absorption and promoting carrier separation, thus achieving the improved photocatalytic activity of g-C3N4-SA. The optimum g-C3N4-SA with the mass of SA 0.05 g (g-C3N4-SA-0.05) presents a high ammonia evolution rate of 7.92 mmol L−1h−1 g−1, 2.5 and 1.4 times than g-C3N4 (3.2 mmol L−1h−1 g−1) and g-C3N4 loaded with Pt (5.47 mmol L−1h−1 g−1). Furthermore, the excellent photostability of g-C3N4-SA is also achieved.
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The practical photocatalytic application of cadmium sulfide (CdS) has been significantly constrained by fast carrier recombination and significant photocorrosion. Therefore, we ...developed a three-dimensional (3D) step-by-step (S-scheme) heterojunction using the coupling interface between purple tungsten oxide (W18O49) nanowires and CdS nanospheres. The photocatalytic hydrogen evolution rate of optimized W18O49/CdS 3D S-scheme heterojunction can reach 9.7 mmol·h−1·g−1, 7.5 and 16.2 times greater than pure CdS (1.3 mmol·h−1·g−1) and 10 wt%-W18O49/CdS (mechanical mixing, 0.6 mmol·h−1·g−1), proving that the tight S-scheme heterojunction constructed by the hydrothermal method can efficiently enhance the carrier separation. Notably, the apparent quantum efficiency (AQE) of W18O49/CdS 3D S-scheme heterojunction approaches 7.5% and 3.5% at 370 nm and 456 nm, respectively, which is 7.5 and 8.8 times than pure CdS (1.0% and 0.4%). The produced W18O49/CdS catalyst also has relative stability of structure and hydrogen production. Additionally, the H2 evolution rate of W18O49/CdS 3D S-scheme heterojunction is 1.2 times greater than 1 wt%-platinum (Pt)/CdS (8.2 mmol·h−1·g−1), which indicates that the W18O49 can effectively replace the precious metal for boosting the hydrogen production rate.
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