Preparation and electrochemical hydrogen storage properties of <scp> Co <sub>9</sub> S <sub>8</sub> </scp> alloy coated with cobalt/graphene composite
Heng Liu, Wanqiang Liu, Peng Chen, Jianxun Zhao, Zhong‐Min Su
Abstract
A facile one-pot reduction process is used to obtain the cobalt/graphene composite (CoRGO). The CoRGO materials exhibit unique reticular globular morphology. Co9S8 hydrogen storage alloy is fabricated via mechanical alloying method. Different amounts of CoRGO are coated on the surface of Co9S8 alloy by ball milling. The electrochemical characterizations of the composites are conducted in the standard tri-electrode system. Ultimately, the CoRGO coated Co9S8 electrode shows preferable performance than the RGO modified alloy (603.6 mAh/g) and original alloy (577.3 mAh/g). As the additive content of CoRGO is 6 wt%, a maximum discharge capacity of 637.5 mAh/g is obtained. Furthermore, the cycle stability and high-rate dischargeability of the electrode are also enhanced. The Co particles in the CoRGO participate in the reversible redox reactions and the graphene provides high conductivity. The CoRGO with distinctive structure and morphology can not only improve the electrocatalytic activity but also increase the specific surface area of Co9S8 alloy. The cobalt and graphene species in the CoRGO composite serve a synergistic effect in further facilitating the hydrogen diffusion, expediting the charge transfer in/on the alloy and improving the corrosion resistance, thus enhancing the electrochemical performance and reaction kinetics of Co9S8 alloy.