3D porous carbon conductive network with highly dispersed Fe-Nxsites catalysts for oxygen reduction reaction.

Intrinsic activity and reactive numbers are considered two important factors in oxygen reduction reaction (ORR) catalysts. Herein, we report the rational design and synthesis of a strongly coupled hybrid material comprising of FeZn nanoparticles (FeZn NPs) supported by a three-dimensional carbon conductive network (FeZn NPs@3D-CN) for increased ORR performance. Fe-N-C sites can offer high intrinsic activity owing to the unique bonding and oxygen vacancies, and the carbon conductive network facilitating the exposure to active sites, and increasing electron transport. Because of the synergetic effect of the conductive networks containing Fe-N-C and polyaniline, the catalysts exhibited ORR activity in an alkaline medium via a four-electron transfer process. FeZn NPs@3D-CN exhibited outstanding performance with a limited current density (6.2 mA cm-2), the Tafel slope (81.19 mV dec-1), and stability (23 mV negative shift after 2000 cycles), which were superior to those of 20% Pt/C (5.7 mA cm-2, 75.1 mV dec-1, 36 mV negative shift after 2000 cycles). This research highlights the effect of conductive networks expanding pathways and reducing the resistance of mass transport, which is a facile method to generate superior ORR electrocatalysts.

Increased dielectric performance of PVDF-based composites by electrochemical exfoliated graphite additives.

Adding conductive graphene into polyvinyliden1 fluoride (PVDF) is an effective method to improve the dielectric properties. However, the high conductivity and uniform distribution of graphene in PVDF matrix still meet challenges. In this work, electrochemical exfoliated graphite (EEG) with good conductivity and solution dispersion is used to prepare PVDF/EEG films. By this method no specific conditions are needed such as reduction or hot press. The dielectric properties and flexibility of PVDF/EEG films of different concentrations of EEG are investigated. Especially, when EEG content is 2.6 wt%, composite film has a high dielectric constant of 86 and a low dielectric loss of 0.9 (100 Hz). Simultaneously, the tensile strength of the film was up to 55.1 MPa. The preparation method is simple and convenient, and the obtained material has high dielectric constant and tensile strength. This method paves the way for the application of flexible electronic sensing equipment.