کلیدواژهها
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azo-azomethine, catalyst, complex, electrochemistry, water oxidation
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چکیده
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Nickel, cobalt, and copper complexes were synthesized by the reaction of metal
acetate salts and azo-azomethine-type ligand H2L (H2L = 4-chloro-1,2-bis
[2-hydroxy-5-(phenylazo)benzylideneamino]benzene). The complexes were
characterized by spectroscopic methods, molar conductivity measurements,
and elemental analysis. The complexes were investigated as water oxidizing
catalysts by several electrochemical techniques. Our findings revealed that the
nature of the central metal ion plays an essential role in the stability of the
complexes and their electrocatalytic activity. Although all modified electrodes
with complexes showed good activities for water oxidation compared with
bare carbon paste electrode, nevertheless, NiL showed a much superior
electrocatalytic activity in basic solution in terms of onset potential and Tafel
slope. Experiments indicated that at pH = 11, NiOx is probably a heterogeneous
catalyst for the oxidizing of water in the presence of NiL. However,
about CoL, it was revealed that a high valent cobalt oxo intermediate is active
in the electrocatalytic process. On the other hand, field-emission scanning
electron microscope images showed the formation of nanorods on the
electrode surface. However, upon our observations, it was difficult to
determine the real role of CoL in the water oxidation reaction. Surprisingly,
the results indicated that CuL is not stable under electrochemical conditions,
and after performing the amperometry for a long time, its electrocatalytic
activity decreases.
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