Self-ordered Mo-oxide Nanotube Arrays as Precursor for Aligned MoOx/MoS2 Core-Shell Nanotubular Structures with a High Density of Reactive Sites

In the present work we demonstrate the self-organized formation of anodic Mo-oxide nanotube arrays grown on a Mo sheet under suitable electrochemical conditions in glycerol/NH4F electrolytes. The resulting amorphous tubes can be crystallized by annealing to MoO2 or MoO3. The tube walls then can be further sulfurized fully or partially to Mo-sulfide to form well-ordered arrays of vertically aligned MoOx/MoS2 nanotubes. Under optimized conditions, defined MoS2 sheets form on the oxide walls in a layer by layer low angle zig-zag arrangement that provide a high density of reactive stacking faults. These core-shell nanotube arrays, consisting of tubes with a conductive suboxide core and a functional high defect density MoS2 coating, are highly promising for applications such as electrocatalysis (hydrogen evolution) or ion insertion devices.