Surface modification of Mg3MnNi2 hydrogen storage electrode alloy with polyaniline

Abstract In this paper, polyaniline (PANI) has been adopted to modify the surface of Mg 3 MnNi 2 hydrogen storage electrode alloy prepared by induction melting via chemical deposition. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) tests were performed to investigate the phase composition and microstructure. The comprehensive analysis based on the results of XRD, SEM, TEM and FT-IR indicates that PANI with a thickness of about 10 nm has been successfully polymerized on the surface of Mg 3 MnNi 2 alloy. The discharge capacity retention ( R 20 ) of the Mg 3 MnNi 2 alloy has been increased from 13.5% to 36.2% after modification with PANI, indicating better cycling stability. The Tafel polarization curves reveal that the surface modification of Mg 3 MnNi 2 alloy with PANI can enhance its anti-corrosion ability. The increase of the exchange current density ( I o ) indicates that the surface activity of Mg 3 MnNi 2 alloy can be improved through the surface modification with PANI. However, the high rate discharge ability (HRD) test shows that the kinetic property of Mg 3 MnNi 2 alloy after the surface modification is declined, which is mainly due to the decline of the hydrogen diffusion in PANI, evidenced by the decreased limit current density ( I L ) obtained from the anodic polarization curves.