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Hollow carbon nanocages (HCNCs) consisting of sp2 carbon shells featured by a hollow interior cavity with defective microchannels (or customized mesopores) across the carbon shells, high specific surface area, and tunable electronic structure, are quilt different from the other nanocarbons such as carbon nanotubes and graphene. These structural and morphological characteristics make HCNCs a new platform for advanced electrochemical energy storage and conversion. This review focuses on the controllable preparation, structural regulation, and modification of HCNCs, as well as their electrochemical functions and applications as energy storage materials and electrocatalytic conversion materials. The metal single atoms-functionalized structures and electrochemical properties of HCNCs are summarized systematically and deeply. The research challenges and trends are also envisaged for deepening and extending the study and application of this hollow carbon material. The development of multifunctional carbon-based composite nanocages provides a new idea and method for improving the energy density, power density, and volume performance of electrochemical energy storage and conversion devices. [ABSTRACT FROM AUTHOR]

An efficient 'in situ growth' strategy was exploited to create the g-CN nanosheets (NSs) and CdS nanorods (NRs) 1-D/2-D hybrid architectures, i.e. CdS NRs/g-CN NSs nanocomposites, from cadmium-containing carbon nitride nanosheets (Cd/g-CN) compounds. The novel polymer/semiconductor hybrid material demonstrates very high photoelectrochemical response under visible light irradiation. The CdS NRs/g-CN NSs electrode displays the largest photocurrent (about 100 μA/cm), which is about 30 times compared with that of pristine g-CN electrode (about 3.5 μA/cm). The maximum incident photon-to-electron conversion efficiency (IPCE) value is up to 27 % for CdS NRs/g-CN NSs electrode, which is much higher than that of pristine g-CN electrode (1.2 %). The elevated photoelectrochemical performances are originated from the direct physical and electronic contact between the interfaces of the two semiconductor nanomaterials. [ABSTRACT FROM AUTHOR]

Abstract Newly three-dimensional (3-D) graphene-like carbon nanosheet network is synthesized by a simple and efficient buried-protection KOH activation technology with a surfactant (Tween-20) as carbon source (molecular precursor). The as-synthesized material possesses favorable three-dimensional network structure and hierarchical porous structure (with a specific surface area of 2017.3 m2 g−1). As a promising supercapacitor electrode, a relatively high specific capacitance of 316.8 F g−1 at a current density of 1 A g−1 in 1 mol L−1 KOH aqueous solution, along with good cycling stability (with a 92.5% retention rate after 2000 cycles) are demonstrated for the as-prepared electrode. The 3-D graphene-like carbon nanosheet network material exhibits ideal capacitive behavior indicating a promising electrode material for high-performance supercapacitors. Graphical abstract Image Highlights • Newly 3-D graphene-like carbon nanosheets are prepared in a large area. • A surfactant (Tween-20) is used as carbon source (molecular precursor). • An efficient buried-protection KOH activation technology is developed. • Excellent electrochemical capacitive performances are demonstrated. [ABSTRACT FROM AUTHOR]