Preparation of porous polyaniline/RGO composite and its application in improving the electrochemical properties of Co9S8 hydrogen storage alloy

The sea urchin-like porous polyaniline (PPANI) is prepared by a facile saturated solution synthetic route. The porous polyaniline/reduced graphene oxide composite (PPANI/RGO) is synthesized via a solution-assisted self-assembly method. Mechanical alloying is used to obtain the Co9S8 alloy. Composites of Co9S8 mixed with PPANI and PPANI/RGO are fabricated through ball-milling to improve the electrochemical performance of Co9S8 alloy. The structures and morphologies of the composite alloys are studied by XRD, SEM and BET. The electrochemical properties of alloys are tested as negative electrodes of Ni-MH batteries by the LAND CT2001A tester and three-electrode system. For comparison, Co9S8 alloys doped with conventional polyaniline (CPANI) and RGO are also prepared. Ultimately, the Co9S8 + PPANI composite shows preferable discharge capacity compared with CPANI modified Co9S8 and matrix alloy. In addition, the PPANI/RGO composite modified Co9S8 electrode exhibits superior discharge capacity than separate PPANI and RGO coated alloys. A maximum discharge capacity (701.4 mAh/g) is achieved for Co9S8 + PPANI/RGO electrode. Furthermore, the Co9S8 + PPANI/RGO composite materials exhibit preferable high-rate dischargeability, improved corrosion and oxidation resistance and excellent kinetics properties. The PPANI material with special porous structure and unique morphology displays better performance than CPANI. Moreover, a synergistic effect between PPANI and RGO species in the PPANI/RGO material may provide a rapid passageway for charge transfer and accelerate the hydrogen transmission. Accordingly, the electrochemical activity and kinetic properties are improved for Co9S8 + PPANI/RGO composite electrode.