Cu(OH)2 and CuO nanotube networks from hexaoxacyclooctadecane-like posnjakite microplates: Synthesis and electrochemical hydrogen storage

Our recent progress shows that Cu(OH)2 and CuO nanoribbon arrays exhibit notable electrochemical hydrogen storage capacities of 180 and 160 mAh/g, respectively, which also suggests that porous or tubular nanostructures can have a higher ability of hydrogen uptake. Two dimensional (2D) networks consisting of crossed Cu(OH)2 nanotubes were prepared by a simple topotactic transformation process, including the fabrication of hexaoxacyclooctadecane-like intermediate posnjakite microplates and their subsequent chemical transformation into Cu(OH)2 nanotube networks, which further dehydrated to produce CuO nanotube networks with partial morphological preservation. The formation of half-tube and half-ribbon structures, nanoribbons, and nanotubes during the transformation processes revealed that the deformations of corrugated posnjakite sheets to give lamellar Cu(OH)2 with rolling into tubular structures could be responsible for the growth of Cu(OH)2 nanotube networks from posnjakite microplates. The Cu(OH)2 and CuO nanotube networks could electrochemically charge and discharge with higher hydrogen storage capacities of 220 and 188 mAh/g than the Cu(OH)2 and CuO nanoribbon arrays at room temperature, respectively, which made them promising candidates for hydrogen storage, high-energy batteries and catalytic fields. Based on the rolling mechanism of layered structural materials, this simple topotactic transformation route might be extendable to the preparation of novel nanotube networks with higher capacities of hydrogen storage if appropriate precursors of numerous materials with layered structures were treated in solution.