No abstract

Cuprous oxide (Cu 2 O) with controlled morphology was synthesized via a hydrothermal method by reducing copper nitrate with formic acid. Reactant concentration, reaction temperature, and time show strong effects on the phase formation and morphology of the products. The products were characterized by X-ray power diffraction (XRD), scanning electron microscope (SEM), and UV-vis diffuse reflectance spectroscopy. The possible crystal growth processes have been proposed. The band gap versus different morphology was also studied.

We synthesized a series of pyrrolidinium based dicationic ionic crystals with high melting point and good thermal stability. Research on the crystal structure shows that there are ordered three-dimensional ionic channels in these crystals which is favorable for the ionic conductor to achieve high conductivity and diffusion coefficient. These ionic crystals are applied to electrolyte as matrix in dye sensitized solar cells, and the influence of crystal structure (including the alkylene chain separating two pyrrolidinium rings and anion) versus the device performances are studied by steady-state voltammography, current-voltage trace, and electrochemical impedance spectroscopy. As the solid state electrolyte, an optimized efficiency of 6.02% have achieved under full sunlight irradiation using ionic crystal [C6BEP][TFSI]2. And the device based on this solid electrolyte shows the excellent long-term stability, maintaining 92% of the initial efficiency after 960 h. This study elucidates fundamental the structure of dicationic crystal and provide useful clues for further improvement of solid-state electrolytes in DSSC.

Sulfur was impregnated into hyper-cross-linked porous polymer (HCP) with a high specific area and unique porous structure. Compared to its inorganic or carbon counterparts, the HCP has a relatively high specific surface area of 1980 m g with a total pore volume of 2.61 cm g, resulting in sulfur content in HCP/S of as high as 80 wt %. As a benefit of the unique HCP structure, the HCP/S composite exhibits a high initial discharge specific capacity (1333 mA h g at 0.2 C), high-rate property, and good cycling stability (658 mA h g after 120 cycles at 0.5 C and 604 mA h g after 80 cycles at 1 C). Furthermore, the capacity of cells loses less than 1% after the first 20 charge/discharge cycles, while the HCP/S cathode can be cycled with an excellent Coulombic efficiency of above 94% after 120 cycles. Compared with pristine sulfur, the superior electrochemical performance of HCP/S composite is related to the cross-linked porous framework. Such structure could provide short ionic/electronic conduction pathways and suppress the polysulfide shuttle during the discharge process.

SnO2 shells with micromesopores are synthesized using the template sacrifice method from silica sphere templates. The pores and specific surface area are characterized with SEM, TEM, and BET absorptions. Sulfur is introduced into the SnO2 shells up to 66 wt % according to TGA results. Extra sulfur can only be located at the outer surface of SnO2, resulting in a drastically reduced specific surface area. Because of the unique structure, the S/SnO2 composites with 66 wt % sulfur content exhibit a high initial capacity of 1517 mA·h·g–1 at a current density of 0.2 C, and 1176 mA·h·g–1 at 0.5 C, and remaining capacity of 1176 and 736.6 mA·h·g–1 after 50 cycles, respectively. The performance is much better than that of pure sulfur or S/SnO2 at higher sulfur content. Better performance of S/SnO2 at 66 wt % is attributed to the micromesopores and the shell framework of SnO2, while the performance fading at higher sulfur content is owing to the coating of extra sulfur on the outer surface of SnO2 shells.