Nickel/graphene/polyaniline composites prepared by one-step electrodeposition as catalysts for methanol oxidation

The traditional catalyst for direct methanol fuel cells (DMFC) is usually platinum, but the high price of noble metals limits the commercialization of DMFC. To develop a non-noble metals catalyst with low cost, simple process and high efficiency for DMFC, the nickel/graphene/polyaniline (NGP) composites were synthesized by one-step electrochemical method under a deposition voltage of 0.5 V for the deposition time ranged from 50 to 250 s. The NGP composite materials was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). The XRD result showed that the crystal peaks of Ni appeared as NGP composite electrodeposited at 0.5 V for 100 s, and the FTIR result indicated that polyaniline has been successfully prepared by electrodeposition at 0.5 V for 100 s. Large Ni crystals with diameters ranging from 1 to 2 μm, which was embedded in graphene sheets coated by polyaniline, can be observed from SEM. Furthermore, their catalytic performance for the oxidation of methanol in an alkaline medium were investigated. The result showed that the NGP composite material prepared under a deposition voltage of 0.5 V and a deposition time of 200 s exhibited excellent catalytic effects for the methanol oxidation reaction. The peak current density of catalytic methanol oxidation reached 5.01 mA/cm². According to chronoamperometric analysis, the current density was stable during 1000 s and finally remained 12.5% of the initial current density, it demonstrated the remarkable stability.