Journal of the Serbian Chemical Society 2013 Volume 78, Issue 12, Pages: 2039-2052
https://doi.org/10.2298/JSC131024123Z
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Unusual behaviour of perflurorinated cobalt phthalocyanine compared to unsubstituted cobalt phthalocyanine for the electrocatalytic oxidation of hydrazine. Effect of the surface concentration of the catalyst on the graphite surface
Zagal José H. (Facultad de Química y Biología, Departamento de Química de los Materiales Universidad de Santiago de Chile, Casilla, Correo, Sucursal Matucana, Santiago, Chile)
Geraldo Daniela A. (Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andrés Bello. República, Santiago, Chile)
Sancy Mamie (Fuerza Aérea de Chile, Academia Politécnica Aeronáutica, José Miguel Carrera, El Bosque, Santiago, Chile)
Paez Maritza A. (Facultad de Química y Biología, Departamento de Química de los Materiales Universidad de Santiago de Chile, Casilla, Correo, Sucursal Matucana, Santiago, Chile)
We have found that CoPc and 16(F)CoPc when adsorbed on graphite electrode
exhibit voltammograms in alkaline solution (0.2M NaOH) that show the typical
redox peaks attributed to the Co(II)/(I) reversible. The peak potential for
CoPc is independent of surface concentration of the catalyst. In contrast,
for 16(F)CoPc the Co(II)/(I) redox process shifts to more negative potentials
when the surface concentration of the catalyst increases. In a volcano
correlation of log (i/G)E (activity per active site) versus Co (II)/(I)
formal potential of catalyst (using several CoN4 chelates) CoPc appears in
the ascending portion (activity increases with the Co (II)/(I) redox
potential) whereas 16(F)CoPc appears in the region where activity decreases
with the redox potential. In a plot of log (i/G)E versus the Co(II)/(I)
formal potential of 16(F)CoPc the declining portion of the volcano is
reproduced for one single complex. So 16(F)CoPc at different surface
concentrations behaves as Co complexes having different redox potential in
the declining portion of the volcano plot, when the activity is normalized
for the surface concentration. This is not observed for CoPc.
Keywords: cobalt phthalocyanine, cobalt-hexadecafluoro-phthalocyanine, surface concentration-dependent redox potential, hydrazine oxidation, electrocatalysis