Reduced graphene oxide supported bimetallic Ni-Co nanoparticles as an electrocatalyst for electro oxidation of methanol in alkaline media

Developments of the fuel cells, batteries, and water electrolyzers which are clean energy conversion and storage technologies, is highly interested subjects for researchers. Because, they can resolve current problems associated with energy security and environmental pollution [1]. Fuel cell technology is developing machinery that can efficiently convert chemical energy into electrical energy with a negligible emission of contaminants. Among different types of fuel cells under development, the direct methanol fuel cell (DMFC) is illustrious by its low operational temperature and suitable fuel feeding. These features permit a potential application to portable electronics such as cell phones, laptop computers, and video camcorders [2]. In the electrochemical oxidation of methanol, the electrode material is clearly an important parameter where a high effective electrocatalyst is needed. Different electrocatalysts based on Pt and Pt-binary electrodes were generally used as a catalyst for the electrochemical oxidation of methanol [3]. Nevertheless, the extensive application of Pt catalyst is seriously limited because of its high cost and easy deactivation from the surface adsorption of poisonous intermediates or reaction products. Applying alloys of low cost metals such as (Fe, Co, Ni, and Cu) can partly solve these problems [4]. Many modified electrodes, in which Ni is used as a structure in their manufacture, can be used as a catalyst in fuel cells. Also, using of graphene nano-sheets as a substrate for deposition of bimetallic nanoparticles make a good nanostructure for catalytic goals. In this study, we have successfully demonstrated the possibility of fabrication Ni-Co nanoparticles on reduce graphene oxide/carbon paste electrode (Ni-Co/RGO/CPE). After characterization of obtained electrode, prepared electrocatalyst was used for electrocatalytic oxidation of methanol. The results showed that the presence of Ni-Co in the structure of catalyst and application of RGO/CPE as a substrate greatly enhance the electrocatalytic activity towards the electrooxidation of methanol. Cyclic voltammetric responses of various modified electrodes were obtained in NaOH solution pH 13.0 in the absence and presence of methanol. The anodic peak potential of methanol oxidation at the bare CPE is more than 1.1 V, while the corresponding potential at Ni-Co/RGO/CPE is about 0.65 V. On the other hand, the anodic peak current at the surface of Ni-Co/RGO/CPE is greatly enhanced by addition of methanol to the solution, while its cathodic peak current disappears. The chronoamperometry technique was employed for obtaining the diffusion coefficient of methanol and the value of 8.75×10-8 cm2s-1 is calculated for it which is comparable with other reports. Also the catalytic rate constant was obtained for the reaction between methanol and Ni-Co/RGO/CPE according to method of Galus as 1.05 M-1s-1.