Prussian blue and its analogues as advanced supercapacitor electrodes

Remarkable attention has been directed to Prussian blue(PB) and its analogues(PBA) as one of the most widely used metal-organic frameworks(MOFs) especially in the field of energy storage devices due to their fabulous features such as 3D open framework, high surface area, controllable distribution of pores and the low cost. Nevertheless, their depressed conductivity causes some insulation when being used as an electrode for supercapacitors leading to be restricted in further applications particularly the electronics. To the best of our knowledge, our review aimed primarily to give a total picture of the research that was done on utilizing PB and PBA for fabricating the electrodes of supercapacitor, studying their synthesis approaches in addition to the hybridization with other materials such as graphene, CNTs and conducting polymer. It also addresses the transformation of PB or PBA into other interesting nanostructures such as oxides, sulfides, and bicomponent of graphitic carbon nitride/metal oxides, as well. Furthermore,It exhibits various avenues for overcoming their disadvantages of bad cycle life, retention rate and not achieving the desired values of energy/power densities opening the door for enlarging the number of researches on their application as supercapacitors.

Study on Quantitative Relationship between Surface Wettability and Frictional Coefficient of Liquid Flowing in a Turbulent Horizontal Pipe

This paper had investigated the effects of surface wettability on the frictional resistance of turbulent horizontal flow for tap water in five pipes made of various materials and four kinds of liquids in a polytetrafluoroethylene(PTFE) pipe,with the same inner diameter of 14 mm. Pressure drops were measured under different flow rates through an experimental flow loop. The contact angles and adhesion work of liquids in contact with pipe surfaces were determined using a contact angle meter. Based on the dimension and regression analyses, two kinds of modified relationships between the frictional coefficient and the surface wettability were established according to the measured results corresponding to tap water in five pipes and four liquids in PTFE pipe. The experimental results show that the surface wettability has some influence on frictional coefficient of the studied liquids flowing in macroscale pipes, and the frictional coefficient decreases with the increase of the contact angle at the same Reynolds number. Meanwhile the effect of wettability on the hydrophobic surface is greater than that on the hydrophilic one. The frictional coefficients predicted by the modified formulas have verified to be in good agreement with the experimental values, the relative errors of which are within ±6% and ±3% for the tap water flowing in five different pipes and four kinds of liquids flowing in PTFE pipe, respectively.

One-pot hydrothermal preparation of hierarchical manganese oxide nanorods for high-performance symmetric supercapacitors

An eco-friendly,new,and controllable approach for the preparation of manganese oxide(a-MnO_(2))nanorods has been introduced using hydrothermal reaction for supercapacitor application.The in-depth crystal structure analysis ofα-MnO_(2) is analyzed by X-ray Rietveld refinement by using Full Prof program with the help of pseudo-Voigt profile function.The developed a-MnO_(2) electrode attains a remarkable capacitance of 577.7 F/g recorded at a current density value of 1 A/g with an excellent cycle life when is used for 10,000 repeated cycles due to the porous nanorod-morphology assisting the ease penetration of electrolyte ions into the electroactive sites.The diffusive and capacitive contributions of the electrode have been estimated by considering standard numerical packages in Python.After successfully assembling the aqueous symmetric supercapacitor(SSC)cell by utilizing the as-preparedα-MnO_(2),an excellent capacitance of 163.5 F/g and energy density of 58.1 Wh/kg at the constant current density of 0.5 A/g are obtained with an expanded potential frame of 1.6 V.Moreover,the cell has exceptionally withstood up to 10,000 cycles with an ultimate capacitance retention of 94.1%including the ability to light an LED for 18 s.Such findings recommend the developed a-MnO_(2) electrode to be a highly felicitous electrode for the field of energy storage.