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Characterization and Analytical Application of Cobalt Pyridinoporfyrazinate as a Non-Platinum Mediator in Hydrogen Electrocatalysis
Klusáčková, Monika
This work reports on the cobalt pyridinoporphyrazinate (CoTmtppa) as a platinum-group metal-free catalyst for hydrogen evolution and oxidation reactions with the possibility of use in hydrogen energy and hydrogen potentiometric sensing. A different interaction of CoTmtppa with various electrode substrates, highly oriented pyrolytic graphite (HOPG) and annealed gold (Au(111)), affects its electrocatalytic behaviour in hydrogen reactions. The formation of a hydride-type complex with the bonding of hydrogen atoms to cobalt centre is supposed to be the rate-determining step. In the case of hydrogen evolution, the maximum catalytic activity of mediator was reached at pH = 11,0, when the HOPG/CoTmtppa showed overpotential decrease by 300 mV and an almost 60-fold increase of current densities compared to HOPG. The electrocatalytic activity of Au(111)/CoTmtppa resulted in a further decrease of overpotential by 175 mV in comparison with HOPG/Co(I)Tmtppa. The electrochemical oxidation of hydrogen was found to depend on hydrogen source which was electrochemically generated on-site or molecular hydrogen supplied from an external source. In the case of electrochemically generated hydrogen, the maximum activity of HOPG/CoTmtppa was reached at pH = 2.1 and an additional it was observed 50 % increase in current...
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Characterization and Analytical Application of Cobalt Pyridinoporfyrazinate as a Non-Platinum Mediator in Hydrogen Electrocatalysis
Klusáčková, Monika
This work reports on the cobalt pyridinoporphyrazinate (CoTmtppa) as a platinum-group metal-free catalyst for hydrogen evolution and oxidation reactions with the possibility of use in hydrogen energy and hydrogen potentiometric sensing. A different interaction of CoTmtppa with various electrode substrates, highly oriented pyrolytic graphite (HOPG) and annealed gold (Au(111)), affects its electrocatalytic behaviour in hydrogen reactions. The formation of a hydride-type complex with the bonding of hydrogen atoms to cobalt centre is supposed to be the rate-determining step. In the case of hydrogen evolution, the maximum catalytic activity of mediator was reached at pH = 11,0, when the HOPG/CoTmtppa showed overpotential decrease by 300 mV and an almost 60-fold increase of current densities compared to HOPG. The electrocatalytic activity of Au(111)/CoTmtppa resulted in a further decrease of overpotential by 175 mV in comparison with HOPG/Co(I)Tmtppa. The electrochemical oxidation of hydrogen was found to depend on hydrogen source which was electrochemically generated on-site or molecular hydrogen supplied from an external source. In the case of electrochemically generated hydrogen, the maximum activity of HOPG/CoTmtppa was reached at pH = 2.1 and an additional it was observed 50 % increase in current...
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Characterization and Analytical Application of Cobalt Pyridinoporfyrazinate as a Non-Platinum Mediator in Hydrogen Electrocatalysis
Klusáčková, Monika ; Nesměrák, Karel (advisor) ; Opekar, František (referee) ; Gál, Miroslav (referee)
This work reports on the cobalt pyridinoporphyrazinate (CoTmtppa) as a platinum-group metal-free catalyst for hydrogen evolution and oxidation reactions with the possibility of use in hydrogen energy and hydrogen potentiometric sensing. A different interaction of CoTmtppa with various electrode substrates, highly oriented pyrolytic graphite (HOPG) and annealed gold (Au(111)), affects its electrocatalytic behaviour in hydrogen reactions. The formation of a hydride-type complex with the bonding of hydrogen atoms to cobalt centre is supposed to be the rate-determining step. In the case of hydrogen evolution, the maximum catalytic activity of mediator was reached at pH = 11,0, when the HOPG/CoTmtppa showed overpotential decrease by 300 mV and an almost 60-fold increase of current densities compared to HOPG. The electrocatalytic activity of Au(111)/CoTmtppa resulted in a further decrease of overpotential by 175 mV in comparison with HOPG/Co(I)Tmtppa. The electrochemical oxidation of hydrogen was found to depend on hydrogen source which was electrochemically generated on-site or molecular hydrogen supplied from an external source. In the case of electrochemically generated hydrogen, the maximum activity of HOPG/CoTmtppa was reached at pH = 2.1 and an additional it was observed 50 % increase in current...
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Characterization of electrode modified by pyridineporphyrazinate film and its utilization in electrochemical sensor
Klusáčková, Monika ; Nesměrák, Karel (advisor) ; Hromadová, Magdaléna (referee)
In the diploma thesis the charge transfer reaction on thin layer N,N',N'',N'''-tetramethyl-tetra-3,4-pyridinoporphyrazinocobalt mediator is studied. The mediator is deposited on electrode surface formed by basal plane of highly ordered pyrolytic graphite. The modified electrode, which displays electrocatalytic activity to oxidation of propylene, has been characterized by cyclic voltammetry, backscattering spectroscopy and atomic force microscopy.
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