Improved electrochemical properties of Co0.9Cu0.1Si hydrogen storage alloy by covering with Co/rGO composite

摘要

Co0.9Cu0.1Si hydrogen storage alloy is fabricated by mechanical alloying method. The cobalt/graphene composite (Co/rGO) is obtained via a facile one-pot reduction process. The Co/rGO materials exhibit unique reticular globular morphology. After ball milling, Co/rGO particles are covered on the Co0.9Cu0.1Si alloy surface. For comparison, Co0.9Cu0.1Si coated with reduced graphene oxide (rGO) is also fabricated. The Co0.9Cu0.1Si + Co/rGO composite exhibits higher discharge capacity than rGO coated alloy (541.6 mAh/g) and matrix Co0.9Cu0.1Si (516.8 mAh/g). A C-max of 582.9 mAh/g is achieved for Co0.9Cu0.1Si + Co/rGO. Electrochemical measurements also show that the high-rate dischargeability and cycle stability are improved. The graphene can provide high conductivity and Co particles in the Co/rGO may participate in the reversible redox reactions. The special structure of Co/rGO may enhance the electrocatalytic activity of the Co0.9Cu0.1Si surface. A synergistic effect between graphene and cobalt species in the Co/rGO composite may be favorable for expediting the charge transfer and facilitating the hydrogen diffusion, thus improving the electrochemical and kinetic properties of Co0.9Cu0.1Si alloy.