Carbon-supported Co-phthalocyanine modified with pyridine, 2-acid pyridine and 2-methyl pyridine as novel cathode catalysts for alkaline PEM fuel cells

Simultaneous determination of theophylline and caffeine on novel [Tetra-(5-chloroquinolin-8-yloxy) phthalocyanato] manganese(III)-Carbon nanotubes composite electrode

This work reports the synthesis of new symmetrically substituted manganese(III) phthalocyanine (2eOHMnPc) (2) containing tetra 5-chloroquinolin-8-yloxy group at the peripheral position for the first time. Manganese(III) phthalocyanine (2) was synthesized by cyclotetramerization of 4-(5-chloroquinolin-8-yloxy)phthalonitrile (1) in the presence of corresponding metal salt (manganese(II) chloride). This peripherally substituted phthalocyanine complex (2) was purified by column chromatography and characterized by several techniques such as IR, mass and UV-Visible spectral data. This novel synthesized phthalocyanine was mixed with multiwalled carbon nanotubes in order to prepare the novel catalytic surface on glassy carbon electrode for theophylline and caffeine detection in acidic medium. The novel composite electrode surfaces were characterized by scanning electron microscopy and electrochemical impedance spectroscopy. Individual and simultaneous determination of theophylline and caffeine were studied by differential pulse voltammetry. The detection limits were individually calculated for theophylline and caffeine as 6.6 × 10^-9 M and 5.0 × 10^-8 M, respectively. In simultaneous determination, LODs were calculated for theophylline and caffeine as 8.1 × 10^-9 M and 3.0 × 10^-7 M, respectively. The practical applicability of the proposed modified electrode was tested for the determination of theophylline and caffeine in green tea, cola and theophylline serum.

Polymer coordination promotes selective CO2 reduction by cobalt phthalocyanine

Cobalt phthalocyanine (CoPc) is a known electrocatalyst for the carbon dioxide reduction reaction (CO2RR) that, when adsorbed onto edge-plane graphite (EPG) electrodes, shows modest activity and selectivity for CO production along with co-generation of H2. In contrast, electrodes modified with CoPc immobilized in a poly-4-vinylpridine (P4VP) film show dramatically enhanced activity and selectivity compared to those modified with CoPc alone. CoPc-P4VP films display a faradaic efficiency of ∼90% for CO, with a turnover frequency of 4.8 s-1 at just -0.75 V vs. RHE. Two properties of P4VP contribute to enhancing the activity of CoPc: (1) the ability of individual pyridine residues to coordinate to CoPc and (2) the high concentration of uncoordinated pyridine residues throughout the film which may enhance the catalytic activity of CoPc through secondary and other outer coordination sphere effects. Electrodes modified with polymer-free, five-coordinate CoPc(py) films (py = pyridine) and with CoPc catalysts immobilized in non-coordinating poly-2-vinylpyridine films were prepared to independently investigate the role that each property plays in enhancing CO2RR performance of CoPc-P4VP. These studies show that a synergistic relationship between the primary and outer coordination sphere effects is responsible for the enhanced catalytic activity of CoPc when embedded in the P4VP membrane.