Combination of porous Co9S8-NC derived from Prussian blue analogue and RGO as effective electrochemical hydrogen storage material

Precipitation method is used to prepare the Prussian blue analogue Co3[Co(CN)6]2 (CoCo-PBA) nanoparticles with three-dimensional cubic structure and uniform size. The porous Co9S8/N-doped carbon (Co9S8-NC) nanostructure is fabricated via heat treatment and sulfidation processes employing CoCo-PBA as the precursor. The porous Co9S8-NC is mixed with RGO by ball milling to further improve the conductivity and electrocatalytic activity. For comparison, the conventional Co9S8 material is synthesized via hydrothermal process. During the electrochemical hydrogen storage test, the porous Co9S8-NC exhibit higher discharge capacity than conventional Co9S8. The conductivity of Co9S8 is enhanced due to the existence of N-doped carbon. The special porous structure and large specific surface area derived from CoCo-PBA provide more electrochemical active sites. Moreover, the electrochemical properties further improve after RGO modification because of the outstanding characteristics of RGO. A highest discharge capacity of 640.8 mAh/g is obtained for the Co9S8-NC/RGO electrode. Additionally, the cycling stability, HRD and kinetic properties are also enhanced with the addition of RGO. As a consequence, Co9S8-NC/RGO can be regarded as a promising material for electrochemical hydrogen storage.