Three-dimensional S-scheme heterojunction by integration of purple tungsten oxide nanowires and cadmium sulfide nanospheres for effective photocatalytic hydrogen generation.

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.

Enhanced Photocatalytic Antibacterial Properties of TiO2 Nanospheres with Rutile/Anatase Heterophase Junctions and the Archival Paper Protection Application.

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.

Transient behavior of compressed magnetorheological brake excited by step currents.

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.

Synthesis of salicylic acid-modified graphite carbon nitride for enhancing photocatalytic nitrogen fixation.

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 â†’ 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.

Two-dimensional/one-dimensional molybdenum sulfide (MoS2) nanoflake/graphitic carbon nitride (g-C3N4) hollow nanotube photocatalyst for enhanced photocatalytic hydrogen production activity.

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.

Gold nanorods/g-C3N4 heterostructures for plasmon-enhanced photocatalytic H2 evolution in visible and near-infrared light.

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.