Electrocatalytic oxidation of methanol on Ni(II)Salen complex encapsulated with type-Y zeolite

• Zeolite Y–Ni(II)(Salen)–graphite–glassy carbon composite electrode was made.
• The composite electrode showed good redox of Ni(III)(Salen)OOH/Ni(II)OH(Salen).
• The electro-catalytic oxidation of methanol in a 1.0 M NaOH solution was studied.
• A mechanism of electro-catalytic oxidation of methanol was proposed.

Type-Y zeolite modified electrode was prepared with the mixture of high pure graphite and the zeolite-encapsulated Ni(II)(Salen) [Salen: N, N′-bis(salicylidene)ethylenediamine] complex as modifier by physical absorption method on the substrate of glassy carbon (GC). The electrochemical characterization of this modified glassy carbon electrode (Ni(Salen)Y/GCE) shows good redox behavior of Ni(III)(Salen)OOH/Ni(II)OH(Salen) couple from cyclic voltammetric experiments. Moreover, electrocatalytic oxidation of methanol at the surface of the Ni(Salen)Y/GCE was studied in a 1.0 M NaOH solution. Compared to bare GCE, Graphite/GCE, NaY/GCE, NiY/GCE, the Ni(Salen)Y/GCE significantly enhanced the anodic current for catalytic oxidation of methanol. The effects of both scan rate and methanol concentration on the anodic peak height of the methanol oxidation were discussed. Also, the mechanism of electrocatalytic methanol oxidation on this modified electrode was proposed to be ECE’ process, which changes from diffusion control at low concentration to a catalytic reaction between the methanol and Ni(III)(Salen)OOH at higher methanol concentration. In addition, the catalytic current is proportional to the concentration of methanol from 0.005 M to 0.3 M. The detection limit and the sensitivity were obtained to be 9.92 mM and 7.27 μA mM−1 form cyclic voltammetry. Finally, using a chronoamperometric method, the catalytic rate constant (kcat) value for electrocatalytic methanol oxidation was found to be 5.48 × 104 cm3 mol−1 s−1.

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