Joongpyo Shim

Preparation and characterization of electrospun LaCoO3 fibers for oxygen reduction and evolution in rechargeable Zn–air batteries

LaCoO3 fibers were synthesized through the calcination of an electrospun polymer-metal precursor fiber. The electrochemical performance of these fibers for oxygen reduction and evolution reactions was characterized in a KOH solution. Additionally, the electrochemical properties were compared with those of a conventional PtRu/C catalyst and a LaCoO3 powder, which was synthesized using the Pechini method. The LaCoO3 fibers had a greater surface area compared with the powder, whereas the crystal structures of the fibers and powder were notably similar. The LaCoO3 fibers demonstrated better electrochemical properties compared with the LaCoO3 powder, which was attributed to the increased surface area and number of active sites in the fibers.

Preparation of Elastic Bipolar Plate for Polymer Electrolyte Fuel Cells

Highly conductive bipolar plate for polymer electrolyte membrane fuel cell (PEMFC) was prepared using phenol novolac-type epoxy/graphite powder (GP)/carbon fiber filament (CFF) composite, and a rubber-modified epoxy resin was introduced to the phenol novolac-type epoxy resin in order to give elasticity to the bipolar plate. The cure condition of the neat epoxy system, differential scanning calorimetry (DSC) was carried out and the DSC data were introduced to Kissinger equation. And tensile and flexural tests were carried out using universal testing machine (UTM) and the surface morphology of the fractured specimen and the interfacial bonding between epoxy matrix and CFF were observed by a scanning electron microscopy (SEM). Kissinger expression showed that the activation energy for the cure kinetics of novolac epoxy (9.3g)/rubber epoxy (1.0g)/curing agent (9.6g)/accelerator (0.1g) system was 76.8 kJ/mol and the pre-exponential factor was 1.73 × 1010 min−1. As was expected, electrical conductivity increased with increasing total carbon content, and the value increased with increasing CFF content at the same carbon content. Tensile strength and flexural strength linearly decreased with increasing epoxy content, however at the same carbon content, these values increased with increasing CFF content. It was because the CFF acted as electrical conductive pass and the good effect on the mechanical properties was due to the strong bonding between CFF and epoxy resin, which was confirmed by the SEM.Copyright