Latest ArticlesA binary-mixed electron transport layer (ETL) has been reported for constructing solution-processable near-infrared organic light-emitting diodes (NIR OLEDs). Relative to the single-component ETL, the binary-mixed ETL composed of PDINN:TPBi can enhance the carrier transport capacity, reduce device impedance, and weaken fluorescence quenching of the emitting layer. By carefully selecting an appropriate luminescent material Y5 (a nonfullerene electron acceptor in organic solar cells) and precisely fine-tuning the molecular aggregation in active layer using a mixed solvent, the morphology is optimized and luminescence performance is enhanced, resulting in efficient NIR OLEDs with an emission peak at 890 nm. The experiment showcases a Y5-based near-infrared OLED with a maximum radiance of 34.9 W sr-1 m-2 and a maximum external quantum efficiency of 0.50%, which is among the highest values reported for non-doped fluorescent NIR OLEDs with an emission peak over 850 nm.
Unraveling the essence of electronic structure effected by d-d orbital coupling of transition metal and methanol oxidation reaction (MOR) performance can fundamentally guide high efficient catalyst design. Herein, density functional theory (DFT) calculations were performed at first to study the d–d orbital interaction of metallic PtPdCu, revealing that the incorporation of Pd and Cu atoms into Pt system can enhance d-d electron interaction via capturing antibonding orbital electrons of Pt to fill the surrounding Pd and Cu atoms. Under the theoretical guidance, PtPdCu medium entropy alloy aerogels (PtPdCu MEAAs) catalysts have been designed and systematically screened for MOR under acid, alkaline and neutral electrolyte. Furthermore, DFT calculation and in-situ fourier transform infrared spectroscopy analysis indicate that PtPdCu MEAAs follow the direct pathway via formate as the reactive intermediate to be directly oxidized to CO2. For practical direct methanol fuel cells (DMFCs), the PtPdCu MEAAs-integrated ultra-thin catalyst layer (4–5 µm thickness) as anode exhibits higher peak power density of 35 mW/cm2 than commercial Pt/C of 20 mW/cm2 (~40 µm thickness) under the similar noble metal loading and an impressive stability retention at a 50-mA/cm2 constant current for 10 h. This work clearly proves that optimizing the intermediate adsorption capacity via d-d orbital coupling is an effective strategy to design highly efficient catalysts for DMFCs.
Fluoride-based electrolyte exhibits extraordinarily high oxidative stability in high-voltage lithium metal batteries (h-LMBs) due to the inherent low highest occupied molecular orbital (HOMO) of fluorinated solvents. However, such fascinating properties do not bring long-term cyclability of h-LMBs. One of critical challenges is the interface instability in contacting with the Li metal anode, as fluorinated solvents are highly susceptible to exceptionally reductive metallic Li attributed to its low lowest unoccupied molecular orbital (LUMO), which leads to significant consumption of the fluorinated components upon cycling. Herein, attenuating reductive decomposition of fluorinated electrolytes is proposed to circumvent rapid electrolyte consumption. Specifically, the vinylene carbonate (VC) is selected to tame the reduction decomposition by preferentially forming protective layer on the Li anode. This work, experimentally and computationally, demonstrates the importance of pre-passivation of Li metal anodes at high voltage to attenuate the decomposition of fluoroethylene carbonate (FEC). It is expected to enrich the understanding of how VC attenuate the reactivity of FEC, thereby extending the cycle life of fluorinated electrolytes in high-voltage Li-metal batteries.
Designing carbon materials with ideal stable hierarchical porous structures and flexible functional properties for efficient and sustainable Zn2+ ion storage still faces great challenges. Herein, the three-dimensional carbon superstructures with spherical nanoflower-like structures were tailor-made by the self-assembly strategy. Specifically, organic polymer units (i.e., organic motifs) were formed by tetrachloro-p-benzoquinone (TBQ) and 2, 6-diamino anthraquinone (DAQ) via a noble-metal-free catalyzed coupling reaction. Subsequently, the organic motifs assemble into spherical nanoflower-like superstructures induced by intermolecular hydrogen bonding and aromatic π-π stacking interactions. Well-designed carbon superstructures can provide a stable backbone that effectively blocks structural stacking and collapse. Meanwhile, the hierarchical porous structures in 3D carbon superstructures provide continuous charge transport pathways to greatly shorten the ion diffusion distance, and as a result, the carbon superstructures-based zinc-ion hybrid capacitors (ZIHCs) provide a capacity of 245 mAh/g at 0.5 A/g, a high energy density of 152 Wh/kg and an ultra-long life of 300, 000 cycles at 20 A/g. The excellent electrochemical performance is also attributed to the corresponding charge storage mechanism, i.e., the alternate binding of Zn2+/CF3SO3− ions. Besides, the high-level N/O motifs improve the surface properties of the carbon superstructures and reduce the ion migration barriers for more efficient charge storage. This paper provides insights into the design of advanced carbon-based cathodes and presents a fundamental understanding of their charge storage mechanisms.
Manipulating catalyst structures to control product selectivity while maintaining high activity presents a considerable challenge in CO2 hydrogenation. Combining density functional theory calculations and microkinetic analysis, we proposed that graphene-supported isolated Pt atoms (Pt1/graphene) and Pt2 dimers (Pt2/graphene) exhibited distinct selectivity in CO2 hydrogenation. Pt1/graphene facilitated the conversion of CO2 into formic acid, whereas Pt2/graphene favored methanol generation. The variation in product selectivity arose from the synergistic interaction of Pt2 dimers, which facilitated the migration of H atoms between two Pt atoms and promoted the transformation from *COOH intermediates to *C(OH)2 intermediates, altering the reaction pathways compared to isolated Pt atoms. Additionally, an analysis of the catalytic activities of three Pt1/graphene and three Pt2/graphene structures revealed that the turnover frequencies for formic acid generation on Pt1ⅱ/graphene and methanol generation on Pt2ⅰ/graphene were as high as 744.48 h-1 and 789.48 h-1, respectively. These values rivaled or even surpassed those previously reported in the literature under identical conditions. This study provides valuable insights into optimizing catalyst structures to achieve desired products in CO2 hydrogenation
Unstable electrode/electrolyte interfaces and heterogeneous Zn deposition would reduce the Coulombic efficiency and cycle life of Zn metal batteries (ZMBs). Applying water-in-salt (WIS) electrolytes has proven to be an effective strategy to address the above issues. However, an understanding of the reaction mechanisms on the Zn anode at nanoscale is still elusive. Here we utilize in situ atomic force microscopy to visualize the solid electrolyte interphase (SEI) formation and Zn deposition/dissolution processes in WIS electrolyte and construct relationships between interfacial behavior and electrochemical performance. The formation processes, chemical properties, and structure of the on-site formed SEI are deeply explored. The SEI with a “plum-pudding” model can guide uniform Zn deposition and reversible dissolution. Mechanistic understanding of the interfacial evolution of the SEI layer and Zn deposition/dissolution has been achieved and will benefit the structural optimization and interfacial engineering of ZMBs.
Self-trapping excitons (STEs) emission in metal halides has been a matter of interest, correlating with the strength of electron-phonon coupling in the lattice, which are usually caused by ions with ns2 electronic structure. In this work, Sb3+/Te4+ ions doped Zn-based halide single crystals (SCs) with two STEs emissions have been synthesized and the possibility of its anti-counterfeiting application was explored. Further, the relationship between the strength of electron-phonon coupling and photoluminescence quantum yields (PLQYs) for STEs in a series of metal halides has been studied. And the semi-empirical range of the Huang-Rhys factors (S) for metal halides with excellent photoluminescence (PL) property has been summarized. This work provides ideas for further research into the relationship between luminescence performance and electron-phonon coupling of metal halides, and also provides a reference for designing the metal halides with high PLQYs.
In the field of lithium-ion battery cathode materials, lithium-rich layered oxide materials have garnered significant attention due to their exceptional discharge specific capacity and high operating voltage. However, their limitations in terms of cycling stability and rate capability remain major impediments to their wider application. In this study, an innovative approach was employed by simultaneously utilizing the acidic and oxidative properties of phosphomolybdic acid to generate a spinel structure and in-situ coating of a conductive polymer (polypyrrole) on the surface of lithium-rich layered oxide materials. This strategy aimed to mitigate structural degradation during charge-discharge cycles, enhance the ionic/electronic conductivity, and suppress side reactions. Experimental results demonstrated that after 200 cycles at a current density of 1 C, the modified sample exhibited a discharge specific capacity of 193.4 mAh/g, with an improved capacity retention rate of 83.3% and a minimal voltage decay of only 0.27 V. These findings provide compelling support for the development and application of next-generation high-performance lithium-ion batteries.
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