Conducting polymers with good electron conductivity and rich redox functional groups are promising cathode candidates for constructing high-energy aqueous zinc batteries. However, the glaring flaw of activesite underutilization impairs their electrochemical performance. Herein, we report a poriferous polytriphenylamine conjugated microporous polymer (CMP) cathode capable of accommodating Cl − anions in a pseudocapativedominated manner for energy storage. Its specific 3D, covalent-organicframework-like conjugated network ensures high accessibility efficacy of N active sites (up to 83.2% at 0.5 A g −1 ) and distinct physicochemical stability (87.6% capacity retention after 1000 cycles) during repeated charging/discharging courses. Such a robust CMP electrode also leads to a zinc dual-ion battery device with a high energy density of 236 W h kg −1 and a maximum power density of 6.8 kW kg −1 , substantially surpassing most recently reported organic-based zinc batteries. This study paves the way for the rational design of advanced CMP-based organic cathodes for high-energy devices.
Covalent organic frameworks (COFs) are potential photocatalysts for artificial photosynthesis but they are much less explored for photocatalytic hydrogen evolution (PHE). COFs, while intriguing due to crystallinity, tunability, and porosity, tend to have low apparent quantum efficiency (AQE) and little is explored on atomistic structure–performance correlation. Here, adopting triphenylbenzene knots and phenyl linkers as a proof of concept, three structurally related COFs with different linkages are constructed to achieve a tunable COF platform and probe the effect of the linkage chemistry on PHE. Cyano‐substituted alkene‐linked COF (COF–alkene) yields a stable 2330 µmol h−1 g−1 PHE rate, much superior to imine‐ and imide‐linked counterparts (<40 µmol h−1 g−1) under visible light irradiation. Impressively, COF–alkene achieves an AQE of 6.7% at 420 nm. Combined femtosecond transient absorption spectroscopy and theoretical calculation disclose the critical role of cyano‐substituted alkene linkages toward high efficiency of charge separation and transfer in the presence of sacrificial electron donors—the decisive key to the superior PHE performance. Such alkene linkages can also be extended to design a series of high‐performance polymeric photocatalysts, highlighting a general design idea for efficient PHE.
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.
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