Here we report a highly scalable yet flexible triple-layer structured porous C/SiO2 membrane via a facile phase inversion method for advancing Li–sulfur battery technology. As a multifunctional current-collector-free cathode, the conductive dense layer of the C/SiO2 membrane offers hierarchical macropores as an ideal sulfur host to alleviate the volume expansion of sulfur species and facilitate ion/electrolyte transport for fast kinetics, as well as spongelike pores to enable high sulfur loading. The triple-layer structured membrane cathode enables the filling of most sulfur species in the macropores and additional loading of a thin sulfur slurry on the membrane surface, which facilitates ion/electrolyte transport with faster kinetics than the conventional S/C slurry-based cathode. Furthermore, density functional theory simulations and visual adsorption measurements confirm the critical role of the doped SiO2 nanoparticles (∼10 nm) in the asymmetric C membrane in suppressing the shuttle effect of polysulfides via chemisorption and electrocatalysis. The rationally designed C/SiO2 membrane cathodes demonstrate long-term cycling stability of 300 cycles at a high sulfur loading of 2.8 mg cm–2 with a sulfur content of ∼75%. This scalable yet flexible self-supporting cathode design presents a useful strategy for realizing practical applications of high-performance Li–S batteries.

A novel amphoteric membrane was designed by blending triple tertiary amine-grafted poly(2,6-dimethyl-1,4-phenylene oxide) (PPO-TTA) with sulfonated poly(ether ether ketone) (SPEEK) for vanadium redox flow batteries. An "acid−base pair" effect is formed by the combination of the tertiary amine group and sulfonic group, and extra nonbonding amine groups could be protonated. Both of them constitute a hydrogen bond network, which facilitates proton conduction and also hinders vanadium permeability because of the lowered swelling ratio and Donnan effect. All these contribute to improve the ion selectivity of the membrane while maintaining ionic conductivity. Compared with other amphoteric and SPEEK-based membranes, the membrane exhibits an excellent performance. The amphoteric membrane containing 15% PPO-TTA exhibits an ultralow vanadium permeability of 3.4 × 10 −9 cm 2 s −1 and a low area resistance of 0.39 Ω cm −2 . Consequently, the cell assembled with this membrane shows excellent performances far superior to SPEEK and Nafion 212. The Coulombic efficiency and energy efficiency of the cell are 94.3−98.3 and 90.3−77.1% at 40−200 mA cm −2 , respectively, and have no significant reductions after 200 cycles. This performance is at a high level among the amphoteric and SPEEK-based membranes reported in recent years. The cell's open circuit voltage is maintained for up to 165 h. In addition, the membrane's chemical stability is improved by the effective barrier to the vanadium ion.

No abstract

No abstract

No abstract

No abstract

TiO 2 nanoparticles with controlled morphology and high photoactivity were prepared using a microemulsion-mediated hydrothermal method in this study, and the particles were characterized by means of TEM, XRD, BET, and BJH analysis. As the hydrothermal temperature is elevated, mean pore diameter, crystalline size, and crystallinity of the particles increase gradually, while the surface area decreases significantly, and the morphology changes from a spherical into a rod-like shape. The morphology transition mechanism of the TiO 2 crystal has been put forward based on a decrease in intensity of the microemulsion interface and an increase in collision efficiency between droplets with increasing the hydrothermal temperature. The photocatalytic activity of the TiO 2 particles synthesized at 120−200 °C is relatively low due to their weak crystallinity, though they have high surface area of 146−225 m 2 /g and small crystalline size of 6−10 nm. However, the TiO 2 samples prepared at 250−350 °C with low surface area (28−90 m 2 /g) exhibit high activity on the degradation of Rhodamine B (RhB), which is comparable or higher than that of the commercial P-25. The reason is ascribed to their high crystallinity that determines material activity in this temperature region. This study reveals that the effects of the surface area, crystallinity, and crystalline size on TiO 2 activity are interdependent, and the balance between these factors is important for improving the photoactivity of the catalyst.

No abstract