Sulfur‐rich carbons are minimally explored for potassium‐ion batteries (KIBs). Here, a large amount of S (38 wt%) is chemically incorporated into a carbon host, creating sulfur‐grafted hollow carbon spheres (SHCS) for KIB anodes. The SHCS architecture provides a combination of nanoscale (≈40 nm) diffusion distances and CS chemical bonding to minimize cycling capacity decay and Coulombic efficiency (CE) loss. The SHCS exhibit a reversible capacity of 581 mAh g−1 (at 0.025 A g−1), which is the highest reversible capacity reported for any carbon‐based KIB anode. Electrochemical analysis of S‐free carbon spheres baseline demonstrates that both the carbon matrix and the sulfur species are highly electrochemically active. SHCS also show excellent rate capability, achieving 202, 160, and 110 mAh g−1 at 1.5, 3, and 5 A g−1, respectively. The electrode maintains 93% of the capacity from the 5th to 1000th cycle at 3 A g−1, with steady‐state CE being near 100%. Raman analysis indicates reversible breakage of CS and SS bonds upon potassiation to 0.01 V versus K/K+. The galvanostatic intermittent titration technique (GITT) analysis provides voltage‐dependent K+ diffusion coefficients that range from 10−10 to 10−12 cm2 s−1 upon potassiation and depotassiation, with approximately five times higher coefficient for the former.

Tuning the catalytic active sites plays a crucial role in developing low cost and highly durable oxygen electrode catalysts with precious metal-competitive activity. In an attempt to engineer the active sites in crystalline structure of Co 3 O 4 spinel for oxygen electrocatalysis in alkaline electrolyte, we provide herein controllable synthesis of surface-tailored Co 3 O 4 nanocrystals including nanocube (NC), nanotruncated octahedron (NTO), and nanopolyhedron (NP) anchored on nitrogen-doped reduced graphene oxide (N-rGO), through a facile and template-free hydrothermal strategy. The as-synthesized Co 3 O 4 NC, NTO and NP nanostructures are predominantly enclosed by {001}, {001}+{111}, and {112} crystal planes, which expose different surface atomic configurations of Co 2+ and Co 3+ active sites. Electrochemical results indicate that the unusual {112} plane enclosed Co 3 O 4 -NP/N-rGO with abundant Co 3+ sites exhibits superior bifunctional activity for dual oxygen reduction and evolution reactions, as well as significantly enhanced metal-air battery performance in comparison with other counterparts. Further experimental and theoretical simulation studies demonstrate that the surface atomic arrangement of Co 2+ /Co 3+ active sites, especially the existence of octahedrally coordinated Co 3+ sites (Co 3+Oh ), optimizes the adsorption, activation, and desorption features of oxygen species, thus contributing to the distinct electrocatalytic properties of different facets enclosed Co 3 O 4 nanocrystals. This work paves the way to obtain highly active, durable and cost-effective electrocatalysts for practical clean energy devices through regulating the surface atomic configuration and catalytic active sites.

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Quantum-dot light-emitting diodes (QLEDs) may combine superior properties of colloidal quantum dots (QDs) and advantages of solution-based fabrication techniques to realize high-performance, large-area, and low-cost electroluminescence devices. In the state-of-the-art red QLED, an ultrathin insulating layer inserted between the QD layer and the oxide electron-transporting layer (ETL) is crucial for both optimizing charge balance and preserving the QDs' emissive properties. However, this key insulating layer demands very accurate and precise control over thicknesses at sub-10 nm level, causing substantial difficulties for industrial production. Here, it is reported that interfacial exciton quenching and charge balance can be independently controlled and optimized, leading to devices with efficiency and lifetime comparable to those of state-of-the-art devices. Suppressing exciton quenching at the ETL-QD interface, which is identified as being obligatory for high-performance devices, is achieved by adopting Zn Mg O nanocrystals, instead of ZnO nanocrystals, as ETLs. Optimizing charge balance is readily addressed by other device engineering approaches, such as controlling the oxide ETL/cathode interface and adjusting the thickness of the oxide ETL. These findings are extended to fabrication of high-efficiency green QLEDs without ultrathin insulating layers. The work may rationalize the design and fabrication of high-performance QLEDs without ultrathin insulating layers, representing a step forward to large-scale production and commercialization.

Constructing heterostructures with abundant interfaces is essential for integrating the multiple functionalities in single entities. Herein, the synthesis of NiSe2/CoSe2 heterostructures with different interfacial densities via an innovative strategy of successive ion injection is reported. The resulting hybrid electrocatalyst with dense heterointerfaces exhibits superior electrocatalytic properties in an alkaline electrolyte, superior to other benchmarks and precious metal catalysts. Advanced synchrotron techniques, post structural characterizations, and density functional theory (DFT) simulations reveal that the introduction of atomic‐level interfaces can lower the oxidation overpotential of bimetallic Ni and Co active sites (whereas Ni2+ can be more easily activated than Co2+) and induce the electronic interaction between the core selenides and surface in situ generated oxides/hydroxides, which play a critical role in synergistically reducing energetic barriers and accelerating reaction kinetics for catalyzing the oxygen evolution. Hence, the heterointerface structure facilitates the catalytic performance enhancement via increasing the intrinsic reactivity of metallic atoms and enhancing the synergistic effect between the inner selenides and surface oxidation species. This work not only complements the understanding on the origins of the activity of electrocatalysts based on metal selenides, but also sheds light on further surface and interfacial engineering of advanced hybrid materials.