Planar Graphene-Based Microsupercapacitors

With the development of wearable, portable, and implantable electronic devices, flexible and on-chip microsupercapacitors (MSCs) are urgently needed for miniaturized energy storage. Planar MSCs have high power density, fast charge/discharge rate, and long operating lifetime, and can adapt to future flexible, integrated, and miniaturized electronic systems for wide application foreground. Due to the high specific surface area, outstanding electrical conductivity, and excellent electron mobility, graphene shows promising advantages in planar MSCs devices, thus stimulates wide-ranging research in the last few years. Herein, the recent progress of planar graphene-based MSCs, including the intrinsic structure regulation of graphene-based electrode materials, the specific fabrication techniques, the multifunctional integration, and various applications of MSCs as flexible and on-chip energy storage is systematically summarized. The key challenges and prospects of future planar graphene-based MSCs are also discussed targeting to realize their practical applications.

Graphitic carbon nitride nanotubes: a new material for emerging applications

We provide a critical review of the current state of the synthesis and applications of nano- and micro-tubes of layered graphitic carbon nitride. This emerging material has a huge potential for light-harvesting applications, including light sensing, artificial photosynthesis, selective photocatalysis, hydrogen storage, light-induced motion, membrane technologies, and can become a major competitor for such established materials as carbon and titania dioxide nanotubes. Graphitic carbon nitride tubes (GCNTs) combine visible-light sensitivity, high charge carrier mobility, and exceptional chemical/photochemical stability, imparting this material with unrivaled photocatalytic activities in photosynthetic processes, such as water splitting and carbon dioxide reduction. The unique geometric GCNT structure and versatility of possible chemical modifications allow new photocatalytic applications of GCNTs to be envisaged including selective photocatalysts of multi-electron processes as well as light-induced and light-directed motion of GCNT-based microswimmers. Closely-packed arrays of aligned GCNTs show great promise as multifunctional membrane materials for the light energy conversion and storage, light-driven pumping of liquids, selective adsorption, and electrochemical applications. These emerging applications require synthetic routes to GCNTs with highly controlled morphological parameters and composition to be available. We recognize three major strategies for the GCNT synthesis including templating, supramolecular assembling of precursors, and scrolling of nano-/microsheets, and outline promising routes for further progress of these approaches in the light of the most important emerging applications of GCNTs.

Synergistic oxygen substitution and heterostructure construction in polymeric semiconductors for efficient water splitting

Herein, we present a synergistic oxygen-substitution and heterostructure construction strategy to produce a two-dimensional oxygenated-triazine-heptazine-conjugated carbon nitride nanoribbon (TOH-CN). The TOH-CN was proved to have an internal donor-acceptor heterostructure that could promote interfacial charge separation and transport, while the oxygen substitution effect modulated the nanoribbon morphology with increased surface/edge active sites and tuned the electronic structure to extend visible-light absorption as well as to improve band structure alignment. Benefiting from these advantages, the TOH-CN served as an efficient bifunctional photocatalyst for both H2 and O2 evolution under visible-light irradiation, exhibiting a 16 times higher photocatalytic H2 evolution rate than that of its melon-based carbon nitride (g-C3N4) counterpart, and a remarkable apparent quantum yield of 7.9% at 420 nm. The O2 evolution rate was 6 times higher than that of g-C3N4, even much higher than those of most bifunctional carbon nitride-based photocatalysts. The developed synergistic strategy of oxygen substitution and heterostructure construction will provide an alternative route for the synthesis of efficient polymeric semiconductors toward efficient solar-to-chemical conversion.