A simple, cheap and effective methanol electrocatalyst based of Mn(II)-exchanged clinoptilolite nanoparticles

Abstract

Clinoptilolite nanoparticles (NClin), prepared via ball-mill mechanical method, were ion-exchanged in Mn(II) solutions with different concentrations ranging from 0.1 to 1 mol L−1. After characterization of samples by XRD, TEM and BET techniques, the resulted Mn-exchanged nano-particles (Mn(II)-NClin) (and also Mn-exchanged micronized one: Mn(II)-MClin) were used for modification of carbon paste electrode (Mn(II)-NClin-CPE). These modified electrodes were applied in methanol oxidation reaction as a catalyst in strong basic pHs which caused to a significant decrease (920 mV) in overvoltage of the process with respect to the bare CPE. The best voltammetric response (CV) was obtained for the catalyst ion exchanged in 1 mol L−1 Mn(II) solution and also by using clinoptilolite nanoparticles with respect to micronized one (MClin). In the chronoamperometris studies, the average diffusion coefficients of 8.73 × 10−3 and 8.6 × 10−5 cm2 s−1 and also the mean ks values of 150 M−1 s−1 and 99 M−1 s−1 were obtained for Mn(II)-NClin/CPE and Mn(II)-MClin/CPE, respectively. CV behavior of the modified electrode was a diffusion controlling process in the absence of methanol, while it was controlled by surface confined process in the presence of methanol, confirming the important role of Mn(OH)2/MnOOH system in electrocatalysis of methanol in alkaline solutions.