Influence of Sn Content, Nanostructural Morphology, and Synthesis Temperature on the Electrochemical Active Area of Ni-Sn/C Nanocomposite: Verification of Methanol and Urea Electrooxidation

Abstract

In contrast to precious metals (e.g., Pt), which possess their electro catalytic activities due to their surface electronic structure, the activity of the Ni-based electrocatalysts depends on formation of an electroactive surface area (ESA) from the oxyhydroxide layer (NiOOH). In this study, the influences of Sn content, nanostructural morphology, and synthesis temperature on the ESA of Sn-incorporated Ni/C nanostructures were studied. To investigate the effect of the nanostructural, Sn-incorporated Ni/C nanostructures, nanofibers were synthesized by electrospinning a tin chloride/nickel acetate/poly (vinyl alcohol) solution, followed by calcination under inert atmosphere at high temperatures (700, 850, and 1000 °C). On the other hand, the same composite was formulated in nanoparticulate form by a sol-gel procedure. The electrochemical measurements indicated that the nanofibrous morphology strongly enhanced formation of the ESA. Investigation of the tin content concluded that the optimum co-catalyst content depends on the synthesis temperature. Typically, the maximum ESA was observed at 10 and 15 wt % of the co-catalyst for the nanofibers prepared at 700 and 850 °C, respectively. Study of the effect of synthesis temperature concluded that at the same tin content, 850 °C calcination temperature reveals the best activity compared to 700 and 1000 °C. Practical verification was achieved by investigation of the electrocatalytic activity toward methanol and urea oxidation. The results confirmed that the activity is directly proportionate to the ESA, especially in the case of urea oxidation. Moreover, beside the distinct increase in the current density, at the optimum calcination temperature and co-catalyst content, a distinguished decrease in the onset potential of both urea and methanol oxidation was observed.