Methanol electrooxidation on glassy carbon electrode modified with bimetallic Ni(II)Co(II)salen complexes encapsulated in mesoporous zeolite A

Nickel and cobalt salen complexes were simultaneously encapsulated in mesoporous zeolite A by flexible ligand method. The prepared catalyst NiCosalenA was investigated for its electrochemical behavior and electrocatalytic activity towards the oxidation of methanol on glassy carbon electrode in 0.1 M NaOH solution. Upon encapsulation in zeolite A, the NiCosalen complex exhibits the typical cyclic voltammetric response, which can be anticipated for the Ni2+Co2+(Salen)(OH)2/Ni3+Co3+(Salen)O(OH) redox couple. It also showed much higher electrocatalytic activity towards the oxidation of methanol than pure NisalenA, due to a synergetic effect that may originate from the interaction of Ni(salen) and Co(salen) and/or the formation of dinuclear salen complexes in adjacent or appropriate sites in a nano-cage through the lattice oxygen of the zeolitic host. The mechanism of electrocatalytic oxidation of methanol on NiCosalenA modified electrode was proposed to be EC process. In both the chronoamperometric and chronocoulometric studies, the reaction of methanol electrooxidation followed a Cottrellian behavior and similar diffusion coefficients (D) of methanol were found to be 3.82 × 10−7 cm2 s−1 and 3.91 × 10−7 cm2 s−1, respectively. The catalytic rate constant (kcat) was also calculated to be 5.52 × 105 cm3 mol−1 s−1 in the range of 0.005–2.0 M of methanol.