Facile and low-cost synthesis route for graphene deposition over cobalt dendrites for direct methanol fuel cell applications

Abstract

In this work, standalone cobalt dendrites are prepared then doped with graphene flakes by a simple electroplating technique. Microstructural examination using SEM with EDX, as well as Raman spectroscopy measurements, verified the successful formation of graphene. The prepared material exhibit a favorably high electrochemical methanol oxidation activity with an onset oxidation potential of 0.07 V vs. Ag/AgCl, which is significantly lower than that of the Ni (0.35 V vs. Ag/AgCl). The doping process causes a decrease in the ohmic resistance of the material from 3.2 Ohm cm−2 to 2 Ohm cm−2, which consequently resulted in a significant increase in the current density from 35 mA cm−2 to 62 mA cm−2 using 1 M methanol at 0.5 V vs. Ag/AgCl. After two hours of current discharge at 0.5 V vs. Ag/AgCl, the catalyst doped with graphene showed a current density of 62 mA cm−2. This is an eight-times higher than that obtained in the case of the Ni nano-powder. An electrode prepared by depositing the catalyst on the surface of a highly conductive porous Ni foam was successfully used as the anode of a passive air cathode direct methanol fuel cell, demonstrating an open circuit voltage of 0.75 V using 0.25 M methanol in 1 M KOH.