A general confinement co-assembly strategy enabling cross-dimensional supraspheres for boosting electrochemical performance

The bottom-up assembly utilizing nanocrystals (NCs) as building blocks is a highly anticipated approach to access novel metamaterials. Limited by the library of binary spherical assembly, colloidal components of building blocks are necessarily extended for targeting the desired assembled-superstructure with emergent properties. Here, a generalized approach is presented that carbon nanotubes (CNTs) capped with long-chain hydrocarbon ligands, as creative colloidal components, can be compatibly co-assembled with various NCs into binary supraspheres based on a confinement microemulsion environment. Such cross-dimensional assemblies possess the structural merits of excellent conductivity, abundant voids and high stability, thus synergistically boosting its electrochemical performance. As a proof of concept, the co-assembled CoFe 2 O 4 /CNTs supraspheres exhibit extraordinary capacity (890 mAh g −1 at 0.5 A g −1 ), rate capability (318 mAh g −1 at 20 A g −1 ), and structural stability (458 mAh g −1 at 5 A g −1 after 1000 cycles) relative to pure CoFe 2 O 4 when evaluated in Li-ion battery. Beyond that, its derived phosphides CoFeP/CNTs assemblies outperform most of the state-of-art electrodes when acting as electrocatalysts for hydrogen evolution reactions (HER). This work provides a new perspective for constructing superstructures of NCs for potential applications in energy storage devices.