RESUMEN
The issues of polysulfide shuttling and lethargic sulfur redox reaction (SROR) kinetics are the toughest obstacles of lithium-sulfur (Li-S) battery. Herein, integrating the merits of increased density of metal sites and synergistic catalytic effect, a unique single-atom catalyst (SAC) with nonmetallic-bonding Fe-Mn diatomic pairs anchored on hollow nitrogen-doped carbonaceous nanodisk (denoted as FeMnDA@NC) is successfully constructed and well characterized by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, X-ray absorption spectroscopy, etc. Density functional theory calculation indicates that the Fe-Mn diatomic pairs can effectively inhibit the shuttle effect by enhancing the adsorption ability retarding the polysulfide migration and accelerate the SROR kinetics. As a result, the Li-S battery assembled with FeMnDA@NC modified separator possesses an excellent electrochemical performance with ultrahigh specific capacities of 1419 mAh g-1 at 0.1 C and 885 mAh g-1 at 3.0 C, respectively. An outstanding specific capacity of 1165 mAh g-1 is achieved at 1.0 C and maintains at 731 mAh g-1 after 700 cycles. Notably, the assembled Li-S battery with a high sulfur loading of 5.35 mg cm-2 harvests a practical areal capacity of 5.70 mAh cm-2 at 0.2 C. A new perspective is offered here to construct advanced SACs suitable for the Li-S battery.
RESUMEN
The commercial applications of lead halide perovskites are hindered by their negative environmental impact and inherent instability. Consequently, developing environmentally friendly copper-based perovskite materials is crucial for future solid-state lighting and display applications. In this study, an ultrafast high-power ultrasonic synthesis strategy was utilized to achieve uniform nucleation and growth of Cs3Cu2X5 (X = Cl, Br, I) nanocrystals (NCs) that possess remarkable luminescence properties, hydroxyl protection, and ligand-free characteristics. These Cs3Cu2X5 NCs exhibited a tunable spectral range spanning from 446 to 525 nm, accompanied by photoluminescence quantum yields (PLQYs) varying from 0.2% to 79.2%. The spectral attributes of the NCs were effectively controlled by modulating the halide type and composition. It is worth noting that density functional theory (DFT) calculations offer valuable insights into the synthesis of NCs and the selection of suitable alcohol solvents. Moreover, we successfully fabricated an efficient and stable white light-emitting diode (WLED) with a high luminous efficiency of 23 lm W-1 and CIE color coordinates of (0.3266, 0.3487). Our work provides a new strategy to synthesize Cs3Cu2X5 NCs and holds promise for their potential application in display and lighting devices.
RESUMEN
Sluggish sulfur redox reaction (SROR) kinetics accompanying lithium polysulfides (LiPSs) shuttle effect becomes a stumbling block for commercial application of LiS battery. High-efficient single atom catalysts (SACs) are desired to improve the SROR conversion capability; however, the sparse active sites as well as partial sites encapsulated in bulk-phase are fatal to the catalytic performance. Herein, high loading (5.02 wt.%) atomically dispersed manganese sites (MnSA) on hollow nitrogen-doped carbonaceous support (HNC) are realized for the MnSA@HNC SAC by a facile transmetalation synthetic strategy. The thin-walled hollow structure (≈12 nm) anchoring the unique trans-MnN2 O2 sites of MnSA@HNC provides a shuttle buffer zone and catalytic conversion site for LiPSs. Both electrochemical measurement and theoretical calculation indicate that the MnSA@HNC with abundant trans-MnN2 O2 sites have extremely high bidirectional SROR catalytic activity. The assembled LiS battery based on the MnSA@HNC modified separator can deliver a large specific capacity of 1422 mAh g-1 at 0.1 C and stable cycling over 1400 cycles with an ultralow decay rate of 0.033% per cycle at 1 C. More impressively, a flexible pouch cell on account of the MnSA@HNC modified separator may release a high initial specific capacity of 1192 mAh g-1 at 0.1 C and uninterruptedly work after the bending-unbending processes.
RESUMEN
Using Mn-doped CsPbCl3 nanocrystals (Mn:CsPbCl3 NCs) to improve perovskite's properties is becoming an important strategy. Here, we demonstrate a modified supersaturated recrystallization route to synthesize high-quality Mn:CsPbCl3 NCs at room temperature. Unprecedentedly, sulfonate ligands with various concentrations are shown to successfully tune the dual-color emission of Mn:CsPbCl3 NCs. Ultrafast transient absorption studies reveal that the host-to-dopant internal energy-transfer process involves the mediated traps. Interestingly, the dual-color emission is tuned via stabilizing mediated traps with a small amount of ligand (band edge (BE) emission reduces and Mn2+ emission increases), passivating the deep traps with a large amount of ligand (Mn2+ emission increases), and destroying Mn:CsPbCl3 NCs with too much ligand (both BE and Mn2+ emission is quenched). Furthermore, the ligand tuning Mn2+ emission exhibits quenching for Cu2+ with high sensitivity and selectivity. Our work provides a new strategy to tune the optical properties of Mn:CsPbCl3 NCs and presents its potential application in an optical detector.