Kee Shyuan Loh

Synthesis and characterization of modified κ-carrageenan for enhanced proton conductivity as polymer electrolyte membrane

Polymer electrolyte membranes based on the natural polymer κ-carrageenan were modified and characterized for application in electrochemical devices. In general, pure κ-carrageenan membranes show a low ionic conductivity. New membranes were developed by chemically modifying κ-carrageenan via phosphorylation to produce O-methylene phosphonic κ-carrageenan (OMPC), which showed enhanced membrane conductivity. The membranes were prepared by a solution casting method. The chemical structure of OMPC samples were characterized using Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1H NMR) spectroscopy and 31P nuclear magnetic resonance (31P NMR) spectroscopy. The conductivity properties of the membranes were investigated by electrochemical impedance spectroscopy (EIS). The characterization demonstrated that the membranes had been successfully produced. The ionic conductivity of κ-carrageenan and OMPC were 2.79 × 10−6 S cm-1 and 1.54 × 10−5 S cm-1, respectively. The hydrated membranes showed a two orders of magnitude higher ionic conductivity than the dried membranes.

Synthesis and Characterization of Sulfonated Graphene Oxide Nanofiller for Polymer Electrolyte Membrane

In this study, sulfonated graphene oxide (SGO) nanocomposite were produced as potential nanofiller to improve the properties of polymer electrolyte membrane (PEM) for fuel cell applications. The GO is produced by modified Hummerss method and the as-synthesized GO was used to prepare SGO with three distinctive precursors, namely 3- mercaptomethoxysilane (MPTMS), sulfanilic acid (SA) and butane sultone (BS). The SGO samples were characterized with several physical characterization techniques (XRD, FTIR, SEM-EDX and XPS) to provide the insights into the morphology; the state of homogenization; the crystallography and the functional groups. The experimental result indicated that the sulfonic acid group has been successfully incorporated with GO and can be used as filler in PEM.

Cobalt-doped carbon xerogel with different initial pH values toward oxygen reduction

In this study, cobalt-doped carbon xerogel (Co-CX) was synthesized via sol-gel polymerization resorcinol-formaldehyde, catalyzed with cobalt nitrate, followed by drying and carbonization process under nitrogen gas flow. The effect of initial pH value (5.5, 6.5 and 7.5) and the type of carbon precursors on the morphology of Co-CX have been investigated with Field Emission-Transmission Electron Microscopy (FESEM). The catalytic activity of Co-CX for the oxygen reduction reaction (ORR) in 0.1 M KOH has been studied by using a rotating ring-disk electrode (RRDE) technique. FESEM revealed that Co doping promotes the formation of more pores. While the conditions allow obtaining xerogel with higher porosity at pH 7.5. The RRDE result display that Co-CX exhibited good catalytic activity tends to favor two electrons pathway.

Effect of nitrogen-doping concentration in carbon nanotubes on cathodic performance for proton exchange membrane fuel cell

Electrode fabricated by N-doped carbon nanotubes has been identified as a potential catalyst for proton exchange membrane fuel cell (PEMFC) application. N-doped carbon nanotubes have shown their ability in electro-reduction of oxygen at the fuel cell cathode. This paper presents a study on the effect of nitrogen-doping level in carbon nanotubes towards the reduction of oxygen. The half cell test studied using cyclic voltammetry analysis has shown a linear relationship between the nitrogen-doping degree in CNT and the cathodic activity. The sample which exhibited the highest cathodic activity was character by its higher structural defects on the surface that is responsible to serve as the active sites for cathodic oxygen reduction reaction.