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Electrocatalytic carbon monoxide reduction (CORR) is effective in achieving renewable synthesis of valuable C2+ species from CO. However, the production of C2+ species is challenged by low activity and selectivity. Here, the surface of the atomically dispersed Cu–Au alloy is functionalized with aromatic heterocycle, thiadiazole derivate (N2SN), to enhance the conversion of CO into C2+ species with acetate as the main product. The N2SN functional groups with electron withdrawing property can alternate the oxidization state of copper, as confirmed by XPS and XAS, thus orienting the CORR pathway to the formation of C2+/acetate. In situ Raman reveals that the N2SN treated sample exhibits stronger signal of *CO intermediate for further dimerization and the C–C–O intermediate relates to acetate formation. Theoretical calculation demonstrates the N2SN molecule doping contributes to lowered energy barrier for C–C coupling, improved activity and selectivity to CORR, and suppressed hydrogen evolution reaction. High Faradaic efficiency (FEC2+, 89%), partial current density (jC2+, 397 mA cm−2), and energy efficiency for C2+ species (EEC2+, 24%) and total current density (jtotal, up to 1000 mA cm−2) are achieved in membrane electrode assembly (MEA), surpassing most of the reported catalysts for total C2+ products. [ABSTRACT FROM AUTHOR]

Aggregation‐induced emission (AIE) and hybridized local and charge‐transfer (HLCT) materials are two kinds of promising electroluminescence systems for the fabrication of high‐efficiency organic light‐emitting diodes (OLEDs) by harnessing "hot excitons" at the high‐lying triplet exciton states (Tn, n ≥ 2). Nonetheless, the efficiency of the resulting OLEDs did not meet expectations due to the possible loss of Tn→Tn−1. Herein, experimental results and theoretical calculations demonstrate the "hot exciton" process between the high‐lying triplet state T3 and the lowest excited singlet state S1 in an AIE material 4⁗‐(diphenylamino)‐2″,5″‐diphenyl‐[1,1″:4′,1″:4″,1′″:4′″,1⁗‐quinquephenyl]‐4‐carbonitrile (TPB‐PAPC) and it is found that the Förster resonance energy transfer (FRET) between two molecules can facilitate the "hot exciton" process and inhibit the T3→T2 loss by doping a blue fluorescent emitter in TPB‐PAPC. Finally, the doped TPB‐PAPC blue OLEDs achieve a maximum external quantum efficiency (EQEmax) of 9.0% with a small efficiency roll‐off. Furthermore, doping the blue fluorescent emitter in a HLCT material 2‐(4‐(10‐(3‐(9H‐carbazol‐9‐yl)phenyl)anthracen‐9‐yl)phenyl)‐1‐phenyl‐1H‐phenanthro[9,10‐d] imidazole (PAC) is used as the emission layer, and the resulting blue OLEDs exhibit an EQEmax of 17.4%, realizing the efficiency breakthrough of blue fluorescence OLEDs. This work establishes a physical insight in the design of high‐performance "hot exciton" molecules and the fabrication of high‐performance blue fluorescence OLEDs. [ABSTRACT FROM AUTHOR]

Substitution of liquid electrolyte with solid‐state electrolytes (SSEs) has emerged as a very urgent and challenging research area of rechargeable batteries. NASICON (Na3Zr2Si2PO12) is one of the most potential SSEs for Na‐ion batteries due to its high ionic conductivity and low thermal expansion. It is proven that the ionic conductivity of NASICON can be improved to 10−3 S cm−1 by Sc‐doping, of which the mechanism, however, has not been fully understood. Herein, a series of Na3+xScxZr2−xSi2PO12 (0 ≤x ≤ 0.5) SSEs are prepared. To gain a deep insight into the ion transportation mechanism, synchrotron‐based X‐ray absorption spectroscopy (XAS) is employed to characterize the electronic structure, and solid‐state nuclear magnetic resonance (SS‐NMR) is used to analyze the dynamics. In this study, Sc is successfully doped into Na3Zr2Si2PO12 to substitute Zr atoms. The redistribution of sodium ions at certain specific sites is proven to be critical for sodium ion movement. For x≤ 0.3, the promotion of sodium ion movement is attributed to sodium ion concentration increase at the Na2 sites and decrease at the Na1 and Na3 sites. For x> 0.3, the inhibition of sodium ion movement is due to the phase change from monoclinic to rhombohedral and an increasing impurity content. [ABSTRACT FROM AUTHOR]

The slow charging limitations of all‐solid‐state lithium batteries (ASSLBs) have significantly limited their practical application. Thus, significant improvement of the rate performance and development of fast charging ASSLBs is crucial for the commercialization of these systems. However, poor Li+ transport kinetics and Li dendrite formation under high charging current densities have inhibited their capabilities. To tackle these issues, the design of dual vertically‐aligned electrodes (DVAEs) is proposed to accelerate Li+ transport and suppress Li dendrite formation. At the anode side, the vertically‐aligned Li (VA‐Li) anode with lithiophilic micro‐walls enables lateral growth of Li deposits rather than perpendicular to the electrode surface, thus preventing dendrite penetration through the separator. In addition, the 3D vertically‐aligned structure in both VA‐Li and vertically‐aligned‐LiFePO4 (VA‐LFP) enables enhanced Li+ transport due to lower tortuosity and faster Li+ transport kinetics. Benefitting from the rational design, VA‐Li symmetric cells can operate for 300 h at a current density/capacity of 3 mA cm−2/3 mAh cm−2, while short‐circuiting is observed after 87 h for bare Li cycled at only 0.5 mA cm−2 (capacity: 0.5 mAh cm−2). Moreover, a fast‐charging ASSLBs assembled with DVAEs demonstrates a high capacity of 89.4 mAh g−1 after 2000 cycles at 4C. [ABSTRACT FROM AUTHOR]

Polymer binders that combine active materials with conductive agents have played a critical role in maintaining the structural integrity of phosphorus anodes with a huge volume change upon sodiation/desodiation. Herein, the role of binders on the structural/chemical stability of phosphorus/carbon anode is spectroscopically uncovered through unexpected mechanism. Surprisingly, the selection of different binders is found to determine the oxidation degree of active phosphorus in various electrodes, which correlate well with their electrochemical properties. At a high oxidation degree, the electrode applying a conventional poly(vinylidene difluoride) binder displays the worst electrochemical properties, while the electrode using a sodium alginate binder delivers the best electrochemical performance (a highly reversible capacity of 1064 mAh g−1 with a 90.1% capacity retention at 800 mA g−1 after 200 cycles and an outstanding rate capability of 401 mAh g−1 at 8000 mA g−1) for its negligible oxidation. Additionally, the emergence/decomposition of surface intermediates, including (PO2)3− and (PO4)3− species, are observed in the discharging/charging processes via the ex situ P K‐edge X‐ray absorption spectroscopies. This novel discovery of the unique role of binders in phosphorus anodes, not only provides an opportunity to ameliorate their electrochemical properties, but also enables their practical applications in high‐energy sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

All‐solid‐state metal batteries (ASSMBs) are attracting much attention due to their cost effectiveness, enhanced safety, room‐temperature performance and high theoretical specific capacity. However, the alkali metal anodes (such as Li and Na) are active enough to react with most solid‐state electrolytes (SSEs), leading to detrimental reactions at the metal–SSE interface. In this work, a molecular layer deposition (MLD) alucone film is employed to stabilize the active Na anode/electrolyte interface in the ASSMBs, limiting the decomposition of the sulfide‐based electrolytes (Na3SbS4 and Na3PS4) and Na dendrite growth. Such a strategy effectively improves the room‐temperature full battery performance as well as cycling stability for over 475 h in Na–Na symmetric cells. The modified interface is further characterized by X‐ray photoelectron spectroscopy (XPS) depth profiling, which provides spatially resolved evidence of the synergistic effect between the dendrite‐suppressed sodiated alucone and the insulating unsodiated alucone. The coupled layers reinforce the protection of the Na metal/electrolyte interface. Therefore, alucone is identified as an effective and bifunctional coating material for the enhancement of the metal/electrolyte interfacial stability, paving the way for rapid development and wide application of high‐energy ASSMBs. [ABSTRACT FROM AUTHOR]

Aggregation‐induced emission (AIE) materials are highly attractive because of their excellent properties of high efficiency emission in nondoped organic light‐emitting diodes (OLEDs). Therefore, a deep understanding of the working mechanisms, further improving the electroluminescence (EL) efficiency of the resulting AIE‐based OLEDs, is necessary. Herein, the conversion process from higher energy triplet state (T2) to the lowest singlet state (SS1) is found in OLEDs based on a blue AIE material, 4′‐(4‐(diphenylamino)phenyl)‐5′‐phenyl‐[1,1′:2′,1′′‐terphenyl]‐4‐carbonitrile (TPB‐AC), obviously relating to the device efficiency, by magneto‐EL (MEL) measurements. A special line shape with rise at low field and reduction at high field is observed. The phenomenon is further clarified by theoretical calculations, temperature‐dependent MELs, and transient photoluminescence emission properties. On the basis of the T2‐S1 conversion process, the EL performances of the blue OLEDs based on TPB‐AC are further enhanced by introducing a phosphorescence doping emitter in the emitting layer, which effectively regulates the excitons on TPB‐AC molecules. The maximum external quantum efficiency (EQE) reaches 7.93% and the EQE keeps 7.57% at the luminance of 1000 cd m−2. This work establishes a physical insight for designing high‐performance AIE materials and devices in the future. [ABSTRACT FROM AUTHOR]

Abstract: Na‐O2 batteries have attracted extensive attention as promising candidates for large‐scale energy storage due to their ultrahigh theoretical energy density. However, the poor cycling performance of Na‐O2 batteries is one of the major challenges facing its future development. A novel Na‐O2 battery using electrically connected carbon paper with Na metal as a protected anode is presented in this study. The O2− crossover from the cathode to anode partially contributes to the limited Coulombic efficiency, as well as the Na corrosion during the cycling process. For the cells with protected Na, the carbon paper maintains a pseudo‐equal potential with the Na metal and works as an artificial protective layer to suppress the detrimental side reactions caused by O2− and O2 crossover toward the Na electrode. Furthermore, the short‐circuiting issue caused by Na dendrite growth also can be completely resolved. Consequently, the Na‐O2 cells with protected Na exhibit two times higher discharge capacity and cycling stability compared with the cells using bare Na. These results indicate the crucial role of the Na anode in determining the overall cell performance and a rational design of anode can dramatically contribute to develop advanced Na‐O2 batteries with longer lifespans and better cycling performance. [ABSTRACT FROM AUTHOR]

Catalysts can play a critical role in the development of sodium-air batteries (SABs). Atomic layer deposition (ALD) technology enables rational design and atomic utilization of catalyst by homogenously distributing catalytically active material on a variety of substrates. Here, a novel hierarchical nanostructured Co3O4 is decorated on carbon nanotubes by ALD (CNT@Co3O4) and used as a catalyst for SABs. CNT@Co3O4 demonstrates better performance and longer cycle life than a mechanically mixed CNT/Co3O4 nanocomposite. Well-dispersed ALD Co3O4 catalyst on CNTs, which serves as functionalized active sites, enables rapid electron exchange and high oxygen reduction/evolution activities. Synchrotron-based X-ray analysis including X-ray absorption near edge structure, extended X-ray absorption fine structure, and scanning transmission X-ray microscopy characterization techniques have been employed to elucidate the activity of Co3O4 and to investigate the nanoscale discharge product distribution found in SABs. This analysis reveals that Co3O4 catalyst can promote the electrochemical decomposition of sodium peroxide, superoxide, and carbonates. The role of the catalyst in SABs is clarified and discussed in detail. [ABSTRACT FROM AUTHOR]

Sodium–air (Na–O2) batteries have recently developed as a high theoretical energy density energy storage and conversion system. In particular, Na–O2 batteries with superoxide as the discharge product have a very high round‐trip energy efficiency over lithium–air batteries due to their significantly reduced charging overpotential. However, Na–O2 batteries yet suffer from limited cycling lives because of the formation and incomplete removal of side products during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes, while the mechanism of these processes is still not fully understood. Herein, a detailed investigation on tracking the decomposition pathway of cubic‐shaped micrometer‐sized NaO2 discharge products in Na–O2 batteries with carbon‐based air electrodes is reported. A detailed electrochemical charging mechanism is revealed during the charging process. The evolution of the chemical compositions of the discharge/side products in air electrode during charging is also verified by synchrotron‐based X‐ray absorption spectroscopy experiments. The formation of these intermediate phases other than NaO2 during the charging process results in high overpotentials. These new findings can contribute to a better understanding and the rational design of future Na–O2 batteries. The oxygen evolution mechanism of micrometer‐sized cubic‐shaped sodium superoxide discharge product in Na–air batteries is clarified. A detailed understanding toward the morphological and chemical composite changes during the charging process is revealed toward their future rational design. [ABSTRACT FROM AUTHOR]

The application of Li‐S batteries is hindered by low sulfur utilization and rapid capacity decay originating from slow electrochemical kinetics of polysulfide transformation to Li2S at the second discharge plateau around 2.1 V and harsh shuttling effects for high‐S‐loading cathodes. Herein, a cobalt‐doped SnS2 anchored on N‐doped carbon nanotube (NCNT@Co‐SnS2) substrate is rationally designed as both a polysulfide shield to mitigate the shuttling effects and an electrocatalyst to improve the interconversion kinetics from polysulfides to Li2S. As a result, high‐S‐loading cathodes are demonstrated to achieve good cycling stability with high sulfur utilization. It is shown that Co‐doping plays an important role in realizing high initial capacity and good capacity retention for Li‐S batteries. The S/NCNT@Co‐SnS2 cell (3 mg cm−2 sulfur loading) delivers a high initial specific capacity of 1337.1 mA h g−1 (excluding the Co‐SnS2 capacity contribution) and 1004.3 mA h g−1 after 100 cycles at a current density of 1.3 mA cm−2, while the counterpart cell (S/NCNT@SnS2) only shows an initial capacity of 1074.7 and 843 mA h g−1 at the 100th cycle. The synergy effect of polysulfide confinement and catalyzed polysulfide conversion provides an effective strategy in improving the electrochemical performance for high‐sulfur‐loading Li‐S batteries. The S/NCNT@Co‐SnS2 material acts as not only an effective shuttle‐suppressing shield for polysulfide but also an electrocatalyst in improving sulfur utilization and cycling stability for high‐sulfur‐loading lithium‐sulfur batteries. Therefore, it maintains 1004.3 mA h g−1 after 100 cycles at a current density of 1.3 mA cm−2. [ABSTRACT FROM AUTHOR]