SURFACE PROPERTIES OF METAL OXIDES AND THEIR ROLE ON ELECTROCHEMICAL HYDROGEN STORAGEOF CARBON NANOTUBES

摘要

Herein, a variety of metal oxides nanoparticles were successfully doped on multi-walled carbon nanotubes (MWCNTs) by incipient-wetness method, and the structure of MWCNTs remained intact as confirmed by XRD data; their surface properties, as well as hydrogen storage were investigated. The data shows a decrease in BET surface area and macroporous volume of NiO, Co3O4 and Fe2O3-MWCNTs composites, as compared to that of acid treated MWCNTs (343.09 m2/g). This is linked with formation of large nanoparticles, that tend to block the MWCNTs passage as revealed by SEM and TEM images. Interestingly the CuO-MWCNTs showed an increase in surface area (558.04 m2/g), and mesoporous volume. This is well linked with small blade-like nanosheet of CuO within and on the surface of acid treated MWCNTs, as revealed by SEM and TEM data. The surface properties of CuO-MWCNTs correlated with high discharge capacity of 159 mAh/g (corresponding to 0.59wt% H2 storage). Although, the discharge capacity values are low, the order of increase correlated with the surface area of the composite as follows: NiO-MWCNTs Co3O4-MWCNTs Fe2O3-MWCNTs CuO-MWCNTs. The discharge capacity of CuO-MWCNTs composite is mainly attributed to the unique surface characteristics and existence of a synergetic interaction between CuO and MWCNTs. The data indicates the need of both mesoporous and macroporous structure of composites for effective hydrogen storage.