Chamunorwa Togo

Applications of polymerized metal tetra-amino phthalocyanines towards hydrogen peroxide detection

This work reports the use of metallo tetra-amino phthalocyanines (MTAPc, M = Co and Mn) polymer thin films on gold and glassy carbon electrode surfaces for the detection and monitoring of hydrogen peroxide (H2O2). The polymer-modified electrodes were characterized using electrochemical and microscopic-based methods. Atomic force microscopy (AFM) was used to study the bare and polymer-modified ITO surfaces. The electrocatalytic reduction of H2O2 with glassy carbon polymer-modified electrodes gave higher current densities compared to their gold counterparts. The electroanalytical properties of H2O2 were obtained using a real-time calibration curve of the amperometric determination in pH 7.4 aqueous solution. The limits of detection (LoD) of the polymer-modified electrodes towards electroreduction of H2O2 were of the order of 10–7 M, with high sensitivity ranging from 6.0–15.4 mA.mM-1.cm-2.

Metallophthalocyanine/carbon nanotube hybrids: extending applications to microbial fuel cells

Pioneering work by Nyokong and others have highlighted the potential benefits for improved electron transfer processes and catalysis of hybrid configurations of metallophthalocyanines with carbon nanotubes. Here we examine the practical application of such hybrid configurations in an Enterobacter cloacae microbial fuel cell. Electrochemical investigations at glassy carbon electrodes (GCEs) showed that FePc and FePc:multiwalled carbon nanotube (MWCNT) hybrid surface modifications display significant oxygen reduction reaction electrocatalytic properties compared to either MWCNT-modified or bare GCE surfaces throughout acidic- to moderately-alkaline pHs. Significant stabilization of the current response at FePc:MWCNT surfaces are notable throughout the pH range, compared to GCE surfaces modified with FePc alone. Corresponding results were obtained for surface modifications of bare carbon paper (BCP) cathodes in a microbial fuel cell where power density increases were observed in the order: Pt > FePc:MWCNT > FePc > MWCNT > BCP. A synergistic combination of simple treatments such as increased ionic strength (300 mM NaCl), temperature (35 °C), and agitation of the anode chamber in this MFC configuration increased the power density to 2.5 times greater than that achieved at platinised cathode configurations under non-optimised conditions, achieving peak power densities of 212 mW.m-2. The long-term stability of the MFC was assessed over 55 days. Surprisingly, the majority of signal loss over extended MFC operation was attributed, in this study, to fouling of the Nafion® PEM membrane rather than either leaching/fouling of the catalysts from the electrodes or nutrient depletion in the anode over the time periods examined.