C2N has emerged as a new family of promising two-dimensional (2D) layered frameworks in both fundamental studies and potential applications. Transforming bulk C2N into zero-dimensional quantum dots (QDs) could induce unique quantum confinement and edge effects that produce improved or new properties. Despite their appealing potential, C2NQDs remain unexplored, and their intriguing properties and a fundamental understanding of their prominent edge effects are still not well understood. Here, we report the first synthesis of water-soluble C2NQDs via a top-down approach without any foreign stabilizer and exploit their linear/nonlinear optical properties and unique edge-preferential electrocatalytic activity toward polysulfides for versatile applications. The resultant dispersant-free C2NQDs with an average size of less than 5 nm feature rich oxygen-carrying groups and active edges, not only enabling excellent dispersion in water but also creating interesting multifunctionality. They can emit not only blue one-photon luminescence (OPL) under ultraviolet (UV) excitation but also green two-photon luminescence (TPL) with a wide near-infrared (NIR) excitation range of 750-900 nm, enabling their use as a new fluorescent ink. Interestingly, when C2NQDs are introduced to modify commercial separators, they can function as new metal-free catalysts to boost polysulfide redox kinetics and endow Li-S batteries with excellent cycling stability, high rate capability, and large areal capacity (7.0 mA h cm–2) at a high sulfur loading of 8.0 mg cm–2. Detailed theoretical and experimental results indicate that the edge of C2N is more favorable for trapping and catalyzing the polysulfide conversion than the terrace and that the synergy between the active edges and oxygenated groups enriched in C2NQDs remarkably improves polysulfide immobilization and catalytic conversion.
We report facile synthesis of low-band-gap mesoporous C 4 Np articles and their use as responsive bifunctional oxygen catalysts for visible-light-sensitive (VLS) rechargeable Zn-air battery (RZAB) and polymer-air battery (RPAB). Compared to widely studied g-C 3 N 4 ,C 4 Nshows asmaller band gap of 1.99 eV,with alarger photocurrent response,and it can function as visible-light-harvesting antenna and bifunctional oxygen reduction/evolution (ORR/OER) catalysts,e nabling effective photocoupling to tune oxygen catalysis.T he C 4 Nenabled VLS-RZAB displays al ow charge voltage of 1.35 V under visible light, which is belowt he theoretical RZAB voltage of 1.65 V, corresponding to ahigh energy efficiency of 97.78 %. Pairing aC 4 Nc athode with ap olymer anode also endows an VLS-RPAB with light-boosted charge performance. It is revealed that the ORR and OER active sites in C 4 Na re separate carbon sites near pyrazine-nitrogen atoms and photogenerated energetic holes can activate OER for improved reaction kinetics.
Herein, we explore an ew redoxd onor-acceptor conjugated microporous polymer (AQ-CMP) by utilizing anthraquinone and benzene as linkers via C-C linkages and demonstrate the first use of CMP as ultralong-lived anodes for rechargeable air batteries.AQ-CMP features an interconnected octupole network, whichaffords not only favorable electronic structure for enhanced electron transport and n-doping activity compared to linear counterpart, but also high density of active sites for maximizing the formula-weight-based redoxc apability.T his coupled with highly cross-linked and porous structure endows AQ-CMP with as pecific capacity of 202 mAh g À1 (96 %o ft heoretical capacity) at 2Ag À1 and % 100 %capacity retention over 60000 charge/discharge cycles. The assembled CMP-air full cell shows as table and high capacity with full capacity recovery after only refreshing cathodes,w hile the decoupled electrolyte and cathode design boosts the dischargevoltage and voltage efficiency to % 1Vand 87.5 %.
Herein, we report the first synthesis of colloidal C4N quantum dots (QDs) and their functional composites and explore their optical activities and edge‐selective polysulfide adsorption‐catalysis. As‐obtained C4NQDs are rich in carbonyl groups and edges, allowing good solution processability and facile assembly with other moieties for creating functionalities. While C4NQDs show normal fluorescence (FL), the QD/poly(vinyl alcohol) (PVA) composites give FL/room‐temperature‐phosphorescence (RTP) dual‐mode emission, enabling the corresponding solution to be used as an encryption ink. The QDs anchored onto carbon nanotubes can be used as a barrier layer to decorate commercial separators, endowing a Li−S cell with excellent cycling stability, high rate capability, and large areal capacity. Computation and experiment studies show that edge sites in C4N favor polysulfide adsorption and catalysis and the enriched edges and carbonyl groups in QDs synergically promotecatalytic conversion of sulfur species.
We report facile synthesis of low-band-gap mesoporous C 4 Np articles and their use as responsive bifunctional oxygen catalysts for visible-light-sensitive (VLS) rechargeable Zn-air battery (RZAB) and polymer-air battery (RPAB). Compared to widely studied g-C 3 N 4 ,C 4 Nshows asmaller band gap of 1.99 eV,with alarger photocurrent response,and it can function as visible-light-harvesting antenna and bifunctional oxygen reduction/evolution (ORR/OER) catalysts,e nabling effective photocoupling to tune oxygen catalysis.T he C 4 Nenabled VLS-RZAB displays al ow charge voltage of 1.35 V under visible light, which is belowt he theoretical RZAB voltage of 1.65 V, corresponding to ahigh energy efficiency of 97.78 %. Pairing aC 4 Nc athode with ap olymer anode also endows an VLS-RPAB with light-boosted charge performance. It is revealed that the ORR and OER active sites in C 4 Na re separate carbon sites near pyrazine-nitrogen atoms and photogenerated energetic holes can activate OER for improved reaction kinetics.
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