G. R. Li

Enhancement of long stability of sulfur cathode by encapsulating sulfur into micropores of carbon spheres

To enhance the long stability of sulfur cathode for a high energy lithium–sulfur battery system, a sulfur–carbon sphere composite was prepared by encapsulating sulfur into micropores of carbon spheres by thermal treatment of a mixture of sublimed sulfur and carbon spheres. The elemental sulfur exists as a highly dispersed state inside the micropores of carbon spheres with a large surface area and a narrow pore distribution, based on the analyses of the X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), thermogravimetry (TG) and local element line-scanning. It is demonstrated from galvanostatic discharge–charge process, cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) that the sulfur–carbon sphere composite has a large reversible capacity and an excellent high rate discharge capability as cathode materials. In particular, the sulfur–carbon sphere composite with 42 wt% sulfur presents a long electrochemical stability up to 500 cycles, based on the constrained electrochemical reaction inside the narrow micropores of carbon spheres due to strong adsorption. Therefore, the electrochemical reaction constrained inside the micropores proposed here would be the dominant factor for the enhanced long stability of the sulfur cathode. The knowledge acquired in this study is important not only for the design of efficient new electrode materials, but also for understanding the effect of the micropores on the electrochemical cycle stability.

Highly Pt-like electrocatalytic activity of transition metal nitrides for dye-sensitized solar cells

Pt-like electrocatalytic activity of MoN, WN, and Fe2N for dye-sensitized solar cells (DSSCs) is demonstrated in this work. Among the transition metal nitrides, MoN has superior electrocatalytic activity and a higher photovoltaic performance. This work presents a new approach for developing low-cost and highly-efficient counter electrodes for DSSCs.

Aluminum storage behavior of anatase TiO2 nanotube arrays in aqueous solution for aluminum ion batteries

The electrochemical aluminum storage of anatase TiO2 nanotube arrays in AlCl3 aqueous solution is investigated. It is firstly demonstrated that aluminum ions can be reversibly inserted/extracted into/from anatase TiO2 nanotube arrays in AlCl3 aqueous solution due to the small radius steric effect of aluminum ions, indicating a potential application in aluminum ion batteries.

One-dimensional hierarchical titania for fast reaction kinetics of photoanode materials of dye-sensitized solar cells

To overcome kinetic limitations of nanoparticles and one-dimensional nanostructures, and enhance fast reaction kinetics of photoanode materials for dye-sensitized solar cells, one-dimensional hierarchical titanate was prepared by coating protonated titanate nanoparticles on one-dimensional protonated titanate nanorods. The one-dimensional hierarchical titania was obtained subsequently after calcination at different temperatures, and was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET). The photoelectrochemical and electrochemical performance of the one-dimensional hierarchical titania was then carried out by photocurrent–voltage curves, electrochemical impedance spectroscopy (EIS), intensity-modulated photovoltage spectroscopy (IMVS) and intensity-modulated photocurrent spectroscopy (IMPS). It is clear that titania nanoparticles grow uniformly on the surface of titania nanorods. The one-dimensional hierarchical titania obtained subsequently can not only provide a matrix similar to the hybrid structure matrix but also avoid forming a large amount of grain boundaries, since the hierarchical structure forms by growth of nanoparticles on nanorods. In particular, the titania with such hierarchical structures after calcination at 600 and 700 °C show optimized fast reaction kinetics: low charge-transfer resistance, fast electron transport and long electron lifetime. The knowledge acquired in this work is important for the design of efficient photoanode materials of dye-sensitized solar cells.