Yolk-Shell Carbon Nanospheres with Controlled Structure and Composition by Self-Activation and Air Activation

Yolk-shell carbon nanospheres (YSCNs) have raised a great deal of interest due to the synergistic advantages over their counterparts. However, it is still difficult to precisely regulate the morphology, porosity, and composition of YSCNs. Here, N-doped porous YSCNs were synthesized via an in situ self-activation by pyrolysis of polypyrrole encapsulated hyper-cross-linked polystyrene (HPS@PPy) core-shell nanospheres, followed by a mild air activation treatment. During the self-activation process, the polypyrrole shell of HPS@PPy provided a confinement effect for the morphology transformation from the core-shell to the yolk-shell structure. The air activation exhibited simultaneous control over porosity and composition. The preparation parameters, such as shell thickness and air activation conditions, were modified to optimize the structure and surface composition of YSCNs to achieve optimal electrochemical performances.

Rational design of asymmetric supercapacitors via a hierarchical core–shell nanocomposite cathode and biochar anode

Hierarchical MnO₂ nanosheets attached on hollow NiO microspheres have been designed by a facile hydrothermal process. The core–shell structure is achieved by decorating an MnO₂ nanosheet shell on a hollow NiO sphere core. The highly hollow and porous structure exhibits a high surface area, shortened ion diffusion length, outstanding electrochemical properties (558 F g⁻¹ at a current density of 5 mA cm⁻²), and excellent cycling stability (83% retention after 5000 cycles). To further evaluate the NiO/MnO₂ core–shell composite electrode for real applications, three asymmetric supercapacitors (NiO/MnO₂//pomelo peel (PPC), NiO/MnO₂//buckwheat hull (BHC), and NiO/MnO₂//activated carbon (AC)) are assembled. The results demonstrated that NiO/MnO₂//BHC delivered a substantial energy density (20.37 W h kg⁻¹ at a power density of 133.3 W kg⁻¹) and high cycling stability (88% retention after 5000 cycles) within a broad operating potential window of 1.6 V.

Hierarchical MnO₂ nanosheets standing on hollow NiO microspheres have been designed by a facile hydrothermal process. Furthermore, asymmetric supercapacitors via core/shell NiO/MnO₂ cathode and biochar anode were assembled.

Unique 1D/3D K2Ti6O13/TiO2 micro-nano heteroarchitectures: controlled hydrothermal crystal growth and enhanced photocatalytic performance for water purification

Unique 1D/3D K₂Ti₆O₁₃/TiO₂ micro-nano heteroarchitectures with enhanced photocatalytic performance for pollutant degradation were successfully fabricated through a controlled hydrothermal route.

Hybrid paper–TiO2 coupled with a Cu2O heterojunction: an efficient photocatalyst under sun-light irradiation

Hybrid paper–TiO₂, paper–Cu₂O–TiO₂ and paper–TiO₂–Cu₂O photocatalysts were prepared via a non-hydrolytic sol–gel process followed by mild hydrothermal treatment to generate the TiO₂ layer, and a reduction process to form the Cu₂O nanoparticles.