Ni(II) decorated nano silicoaluminophosphate molecular sieves-modified carbon paste electrode as an electrocatalyst for electrooxidation of methanol

In this work, we reported a method for the synthesis of nanosized silicoaluminophosphate (SAPO) molecular sieves that are important members of zeolites family. The synthesized SAPO was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) as well as infrared (IR) techniques. Then, the modified carbon paste electrode was prepared by nano SAPO molecular sieves and nickel (II) ion incorporated at this electrode. The electrochemical behaviour of the modified electrode (Ni-SAPO/CPE) towards the oxidation of methanol was investigated by cyclic voltammetry and chronoamperometry methods. It has been found that the oxidation current is extremely increased by using Ni-SAPO/CPE compared to the unmodified Ni-CPE, it seems that Ni2+ inclusion into nano SAPO channels provides the active sites for catalysis of methanol oxidation. The effect of some parameters such as scan rate of potential, concentration of methanol, amount of SAPO was investigated on the oxidation of methanol at the surface of modified electrode. The values of electron transfer coefficient, charge-transfer rate constant and electrode surface coverage for the Ni(II)/Ni(III) couple in the surface of Ni-SAPO/CPE were found to be 0.555, 0.022 s−1 and 5.995 × 10−6 mol cm−2, respectively. Also, the diffusion coefficient and the mean value of catalytic rate constant for methanol and redox sites of modified electrode were obtained to be 1.16 × 10−5 cm2 s−1 and 4.62 × 104 cm3 mol−1 s−1, respectively. The good catalytic activity, high sensitivity, good selectivity and stability and easy in preparation rendered the Ni-SAPO/CPE to be a capable electrode for electrocatalytic oxidation of methanol.