Fabrication of porous polyaniline/MWCNTs coated Co9S8 composite for electrochemical hydrogen storage application

Abstract

Mechanical alloying is used to obtain the Co9S8 hydrogen storage material. The porous polyaniline (PPANI) with sea urchin-like morphology is synthesized via a facile saturated solution synthetic route. The porous polyaniline/multi-walled carbon nanotubes (PPANI/MWCNTs) composite is prepared by a solution-assisted self-assembly route. In order to improve the electrochemical performance of Co9S8, composites of Co9S8 doped with PPANI, MWCNTs and PPANI/MWCNTs are fabricated by ball-milling. As the negative electrodes of Ni-MH batteries, the electrochemical properties of samples are measured utilizing a three-electrode system with the LAND CT2001A tester. Eventually, the composites exhibit superior discharge capacities than original Co9S8 material. Moreover, PPANI/MWCNTs coated Co9S8 electrode shows preferable discharge capacity compared with single MWCNTs or PPANI modified Co9S8. The Co9S8 + PPANI/MWCNTs electrode obtains a maximum discharge capacity of 689.2 mAh/g. In addition, the better high-rate dischargeability, enhanced corrosion resistance and preferable kinetic performance are also obtained for Co9S8 + PPANI/MWCNTs. The improved electrochemical activity and kinetic properties of Co9S8 are attributed to the synergistic effect between PPANI and MWCNTS species, which may further accelerate the hydrogen transmission and promote the charge transfer during the charge/discharge process.