Abstract
Improvement of the electrocatalytic activity of nickel toward methanol oxidation can be conducted by exploiting the synergetic influence of a co-catalyst and/or utilizing a proper support. In this study, utilizing tin as a co-catalyst and supporting on carbon nanofibers are proposed to enhance methanol oxidation in the alkaline media. Typically, NiSn nano particles alloy-incorporated carbon nanofibers could be prepared by calcination of electrospun nanofibers composed of poly (vinyl alcohol), nickel acetate tetrahydrate and tin chloride under argon atmosphere at a high temperature. The influence of the co-catalyst content and the calcination temperature on the morphology, composition and electrocatalytic activity of the proposed nanofibers was investigated. Smooth electrospun nano fibers can be prepared regardless the tin chloride content up to 35 wt%, and the calcination process did not distinctly affect the nanofibrous morphology. Mostly, Ni3Sn and Ni3Sn2 nanoparticles-incorporated amorphous carbon nanofibers were obtained at all the utilized calcination temperatures (700, 850 and 1000 degrees C) and examined SnCl2 contents. However, at 10 wt% SnCl2 content and 850 degrees C calcination temperature, single metallic compound (Ni3Sn2)-incorporated carbon nanofibers were synthesized. Electrochemical measurements indicated that the electrocatalytic activity depends strongly on the tin content as well as the calcination temperature. The nanofibers obtained from electrospun solution containing 10 wt% SnCl2 and calcined at 850 degrees C showed very good performance compared to the other formulations. Typically, the corresponding onset potential of the methanol oxidation reaction using these nanofibers catalyst is 315 mV (vs. Ag/AgCl) while it was 405 mV for the nanofibers obtained from electrospun solution containing 0, 5, 15, 25 and 35 wt% SnCl2. Moreover, the best nanofibers reveal the highest current density. Kinetic study indicated that the corresponding activation energy is 15.6 kJ/mol. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.