查看更多>>摘要：A straightforward approach for preparing a hierarchical carbon nanofiber (CNF) electrode through surface engineering of a stainless steel microwire mesh (SS) current collector is developed. Surface-engineering is achieved via controlled chemical etching SS and subsequent flame depsotion of a CNF coating. In contrast to pristine SS, the surface-engineered SS do not only comprise a unique surface texture but also a higher catalytic activity facilitating the direct growth of CNFs in an ethanol flame. Therefore, the as-fabricated electrode exhibits a high specific capacitance of 2988 F/g at 25 mA/cm(2) in a redox active electrolyte containing Fe2+/(3+) optimized for this electrode/electrolyte system. To maximize their capacitive performance, supercapacitors in a newly designed dual-asymmetric electrode/electrolyte (DASCs) configuration are assembled. Both the CNF positive electrode and the alpha-molybdenum oxide (MoO3) nanobelt negative electrode are capable to operate in their most suitable electrolyte. Consequently, the DASCs deliver an ultrahigh energy density of 96 Wh/kg at 114 W/Kg and a remarkable capacitance retention. Our results demonstrate the effectiveness of this surface engineering approach for fabricating electrodes, the redox activity modulation of the electrolyte, and the newly designed configuration of the capacitors, on enhancing their performance.
查看更多>>摘要：The growth processes of trivalent chromium-based conversion (TCC) coatings on galvanized steel at room temperature (298.15 K) were studied using the potential-time curve, polarization curves, electrochemical impedance spectroscopy and scanning electron microscopy. Results display the integrity of bi-layers at stage II around 50 s causes enhanced corrosion resistance and film compactness. The protection of surficial film, dominated by inner Cr(III)-rich barrier layer, is weakened after stage III, where it presents defective bi-layers with the mixed kinetic-diffusion control. Thermodynamic stability, layer growth and structural evolution of the film formation above Zn are discussed by the Pourbaix diagrams, molecular dynamics and schematic models, respectively.
NSTL
Elsevier