Surface modification of tin oxide through reduced graphene oxide as a highly efficient cathode material for magnesium-ion batteries.

Among post-lithium ion technologies, magnesium-ion batteries (MIBs) are receiving great concern in recent years. However, MIBs are mainly restrained by the lack of cathode materials, which may accommodate the fast diffusion kinetics of Mg2+ ions. To overcome this problem, herein we attempt to synthesize a reduced graphene oxide (rGO) encapsulated tin oxide (SnO2) nanoparticles composites through an electrostatic-interaction-induced-self-assembly approach at low temperature. The surface modification of SnO2 via carbonaceous coating enhanced the electrical conductivity of final composites. The SnO2-rGO composites with different weight ratios of rGO and SnO2 are employed as cathode material in magnesium-ion batteries. Experimental results show that MIB exhibits a maximum specific capacity of 222 mAhg-1 at the current density of 20 mAg-1 with a good cycle life (capacity retention of 90%). Unlike Li-ion batteries, no SnO2 nanoparticles expansion is observed during electrochemical cycling in all-phenyl-complex (APC) magnesium electrolytes, which ultimately improves the capacity retention. Furthermore, ex-situ x-ray diffraction and scanning electron microscopy (SEM) studies are used to understand the magnesiation/de-magnesiation mechanisms. At the end, SnO2-rGO composites are tested for Mg2+/Li+ hybrid ion batteries and results reveal a specific capacity of 350 mAhg-1 at the current density of 20 mAg-1. However, hybrid ion battery exhibited sharp decay in capacity owing to volume expansion of SnO2 based cathodes. This work will provide a new insight for synthesis of electrode materials for energy storage devices.

Facile synthesis of N/B-double-doped Mn2O3 and WO3 nanoparticles for dye degradation under visible light.

In the present work, nitrogen-doped and nitrogen-boron-double-doped manganese oxide (Mn2O3) and tungsten oxide (WO3) nanoparticles were synthesized using precipitation-hydrothermal method for methylene blue degradation under visible light. Materials were characterized using X-ray diffraction (XRD) analysis, Scanning electron microscopy, Energy dispersive X-ray spectroscopy and UV-vis spectroscopy. Results showed that N and B were successfully incorporated into the crystal lattices of Mn2O3 and WO3. XRD showed that WO3 was crystallized in the form of a monoclinic lattice, while cubic Mn2O3 was produced in the cubic form. The crystallite size was found to be decreased due to the substitution of N and B elements which reveals their roles to accelerate the crystal nucleation rate resulting in the decreased size. On the other hand, single and double doping has successfully narrowed the band gaps of the as-synthesised metal oxide photocatalysts resulting in better absorption in the visible light. Band gaps obtained were as follows: 3.02, 2.50, 1.73 and 1.77 eV for N-WO3 N/B-WO3, N-Mn2O3 and N/B-Mn2O3 respectively. Photocatalytic experiments showed that all as-synthesised materials exhibited a photocatalytic efficiency under visible light ≥420 nm. The degradation efficiency of methylene blue (MB) was in the following order: N-B-co-doped metal oxides > N-doped metal oxides > metal oxides. The presence of scavenger molecules such as isopropanol, EDTA-2Na and benzoquinone inhibited MB degradation. Finally, the results showed that these materials can be reused several times without a notable decrease in efficiency.

Strategies for Efficient Charge Separation and Transfer in Artificial Photosynthesis of Solar Fuels.

Converting sunlight to solar fuels by artificial photosynthesis is an innovative science and technology for renewable energy. Light harvesting, photogenerated charge separation and transfer (CST), and catalytic reactions are the three primary steps in the processes involved in the conversion of solar energy to chemical energy (SE-CE). Among the processes, CST is the key "energy pump and delivery" step in determining the overall solar-energy conversion efficiency. Efficient CST is always high priority in designing and assembling artificial photosynthesis systems for solar-fuel production. This Review not only introduces the fundamental strategies for CST but also the combinatory application of these strategies to five types of the most-investigated semiconductor-based artificial photosynthesis systems: particulate, Z-scheme, hybrid, photoelectrochemical, and photovoltaics-assisted systems. We show that artificial photosynthesis systems with high SE-CE efficiency can be rationally designed and constructed through combinatory application of these strategies, setting a promising blueprint for the future of solar fuels.