Photo-rechargeable batteries and supercapacitors:Critical roles of carbon-based functional materials

As a clean and renewable energy source,solar energy is a competitive alternative to replace conventional fossil fuels.Nevertheless,its serious fluctuating nature usually leads to a poor alignment with the actual energy demand.To solve this problem,the direct solar-to-electrochemical energy conversion and storage have been regarded as a feasible strategy.In this context,the development of high-performance integrated devices based on solar energy conversion parts(i.e.,solar cells or photoelectrodes)and electrochemical energy storage units(i.e.,rechargeable batteries or supercapacitors[SCs])has become increasingly necessary and urgent,in which carbon and carbon-based functional materials play a fundamental role in determining their energy conversion/storage performances.Herein,we summarize the latest progress on these integrated devices for solar electricity energy conversion and storage,with special emphasis on the critical role of carbon-based functional materials.First,principles of integrated devices are introduced,especially roles of carbon-based materials in these hybrid energy devices.Then,two major types of important integrated devices,including photovoltaic and photoelectrochemicalrechargeable batteries or SCs,are discussed in detail.Finally,key challenges and opportunities in the future development are also discussed.By this review,we hope to pave an avenue toward the development of stable and efficient devices for solar energy conversion and storage.

Clustering behavior of solid particles in two-dimensional liquid-solid fluidized-beds

In this paper, the clustering behavior of solid particles in a two-dimensional （2D） liquid-solid fluidized-bed was studied by using the charge coupled devices （CCD） imaging measuring and processing technique and was characterized by fractal analysis. CCD images show that the distribution of solid particles in the 2D liquid-solid fluidised-bed is not uniform and self-organization behavior of solid particles was observed under the present experimental conditions. The solid particles move up in the 2D fluidized-bed in groups or clusters whose configurations are often in the form of horizontal strands. The box fractal dimension of the cluster images in the 2D liquid-solid fluidized-bed increases with the rising of solid holdup and reduces with the increment of solid particle diameter and superficial liquid velocity. At given solid holdup and solid particle size, the lighter particles show smaller fractal dimensions.