Bidentate Coordination Structure Facilitates High-Voltage and High-Utilization Aqueous Zn-I2 Batteries.

The zinc-iodine aqueous battery is a promising energy storage device, but the conventional two-electron reaction potential and energy density of the iodine cathode are far from meeting practical application requirements. Given that iodine is rich in redox reactions, activating the high-valence iodine cathode reaction has become a promising research direction for developing high-voltage zinc-iodine batteries. In this work, by designing a multifunctional electrolyte additive trimethylamine hydrochloride (TAH), a stable high-valence iodine cathode in four-electron-transfer I-/I2/I+ reactions with a high theoretical specific capacity is achieved through a unique amine group, Cl bidentate coordination structure of (TA)ICl. Characterization techniques such as synchrotron radiation, in-situ Raman spectra, and DFT calculations are used to verify the mechanism of the stable bidentate structure. This electrolyte additive stabilizes the zinc anode by promoting the desolvation process and shielding mechanism, enabling the zinc anode to cycle steadily at a maximum areal capacity of 57 mAh cm-2 with 97% zinc utilization rate. Finally, the four-electron-transfer aqueous Zn-I2 full cell achieves 5000 stable cycles at an N/P ratio of 2.5. The unique bidentate coordination structure contributes to the further development of high-valence and high capacity aqueous zinc-iodine batteries.

Insight into the Dynamic Nature of the Pt-CeO2 Interface in Dry Reforming of Methane.

Single-atom catalysts (SACs) are attractive in one-carbon (C1) chemistry because of their high atom efficiency. However, it is a great challenge for understanding the dynamic roles of SACs under operating conditions. Here, isolated Pt atoms trapped on defective CeO2 surface are investigated by experiments, especially operando techniques, which offers basic understanding of the nature and dynamic evolution of the Pt-CeO2 interface in dry reforming of methane (DRM). The Pt-Olattice configuration is highly active for CH4 dissociation at the expense of the Olattice atoms, which in turn promotes the H-assisted dissociation of CO2. The transformation of Pt atoms between positive and metallic states is driven by the DRM reaction, which is essential for rendering highly efficient catalysis. The dynamic evolution of Pt atoms favors to eliminate the reactive intermediates, such as carbonates and formates. The dynamic nature of the Pt-CeO2 interface in the DRM reaction shows a similar picture to the Yin and Yang transformation in ancient Chinese Tai Ji wisdom.

Highly Stable SnO2-Based Quantum-Dot Light-Emitting Diodes with the Conventional Device Structure.

ZnO-based electron-transporting layers (ETLs) have been universally used in quantum-dot light-emitting diodes (QLEDs) for high performance. The active surface chemistry of ZnO nanoparticles (NPs), however, leads to QLEDs with positive aging and unacceptably poor shelf stability. SnO2 is a promising candidate for ETLs with less reactivity, but NP agglomeration in nonionic solvents makes the conventional device structure abandoned, resulting in QLEDs with extremely low operational lifetimes. The large barrier for electron injection also limits the electroluminescence efficiency. Here, we report one solution to all the above-mentioned problems. Owing to the strong HO-SnO2 coordination and the steric effect provided by the hydrocarbon groups, tetramethylammonium hydroxide can stabilize SnO2 NPs in alcohol, while its intrinsic dipole induces a favorable electronic-level shift for charge injection. The SnO2-based devices, with the conventional structure, exhibit not only the most efficient electroluminescence among ZnO-free QLEDs but also an operational lifetime (T95) over 3200 h at 1000 cd m-2, which is comparable with that of state-of-the-art ZnO-based devices. More importantly, the superior shelf stability means that the TMAH-SnO2 NPs are promising to enable QLEDs with real stability.

Highly Emissive Quasi-2D Perovskites Enabled by a Multifunctional Molecule for Bright Light-Emitting Diodes.

Quasi-two-dimensional (quasi-2D) perovskite has exhibited great potential to be an ideal luminescent material for perovskite light-emitting diodes (PeLEDs). However, the low-order phases (especially n = 1 phase) and the inevitable defects result in massive nonradiative recombination and poor emission efficiency. Herein, a multifunctional molecule of tetrabutylammonium dihydrogen phosphate (TDP) is introduced to simultaneously suppress the low-n phase, passivate the defects, and increase the exciton binding energy of the quasi-2D perovskite for massive radiative recombination and thus high emission efficiency. The multifunctional roles of TDP are realized by the synergistic effects of tetrabutylammonium cation and dihydrogen phosphate anion, both of which show strong interaction with the lead bromide octahedron of the perovskite. As a result, the TDP-incorporated perovskite films show a great enhancement of the emission efficiency with a remarkable increase in photoluminescence quantum yield (PLQY) from 34.6 to 96.9% at the wavelength of 522 nm. The strengthened radiative recombination promotes efficient emission efficiency with over 2.5-fold improvement in external quantum efficiency (EQE) and current efficiency (CE) from 3.27% and 10.83 cd A-1 to 9.25% and 28.35 cd A-1, respectively, as well as high brightness with over 37% enhancement from 12713 to 17536 cd m-2. Consequently, this work contributes to an efficient approach to employ a multifunctional molecule for highly emissive quasi-2D perovskites and enhanced quasi-2D PeLED performances.

Engineering Ion Diffusion by CoS@SnS Heterojunction for Ultrahigh-Rate and Stable Potassium Batteries.

Transitional metal sulfides (TMSs) are considered as promising anode candidates for potassium storage because of their ultrahigh theoretical capacity and low cost. However, TMSs suffer from low electronic, ionic conductivity and significant volume expansion during potassium ion intercalation. Here, we construct a carbon-coated CoS@SnS heterojunction which effectively alleviates the volume change and improves the electrochemical performance of TMSs. The mechanism analysis and density functional theory (DFT) calculation prove the acceleration of K-ion diffusion by the built-in electric field in the CoS@SnS heterojunction. Specifically, the as-prepared material maintains 81% of its original capacity after 2000 cycles at 500 mA g-1. In addition, when the current density is set at 2000 mA g-1, it can still deliver a high discharge capacity of 210 mAh g-1. Moreover, the full cell can deliver a high capacity of 400 mAh g-1 even after 150 cycles when paired with a perylene-3,4,9,10-tetracarboxydiimide (PTCDI) cathode. This work is expected to provide a material design idea dealing with the unstable and low rate capability problems of potassium-ion batteries.

High-Potential Cathodes with Nitrogen Active Centres for Quasi-Solid Proton-Ion Batteries.

Although proton-ion batteries have received considerable attention owing to their reliability, safety, toxin-free nature, and low cost, their development remains in the early stages because of lacking proper electrolytes and cathodes for facilitating a high output voltage and stable cycle performance. We present a novel cathode based on active nitrogen centre, which provides a flat discharge plateau at 1 V with a capacity of 115 mAh g-1 and excellent stability. Moreover, a quasi-solid electrolyte was developed to overcome the issue of corrosion, broaden the potential window of the electrolyte, and prevent the active material from dissolving. While using the unique as-developed electrolyte, the newly designed cathode retained 89.67 % of its original capacity after 2000 cycles. Finally, we demonstrated the excellent cycle performance of the as-developed metal-free, flexible, soft-packed battery. Notably, even when a portion of the battery was cut off, it continued to function normally.

Ultra-Thermostability of Spatially Confined and Fully Protected Perovskite Nanocrystals by In Situ Crystallization.

Although all-inorganic perovskite materials present multiple fascinating optical properties, their poor stability undermines their potential application in the field of multi-color display. Herein, spatially confined CsPbBr3 nanocrystals are in situ crystallized within uniform mesoporous SiO2 nanospheres (MSNs) to regulate their size distribution, passivate their surface defects, shield them from water/oxygen, and more importantly, enhance their thermotolerance. As a result, the remnant PL intensity of the prepared spatially confined perovskite (CsPbBr3 ) nanocrystals by in situ crystallization within uniform mesoporous SiO2 nanospheres (SCP@MSNs) powders can be maintained over 98% of its initial value even after being immersed in harsh conditions (0.1 m HCl or 0.1 m NaOH) for 60 days. Furthermore, the prepared SCP@MSNs-PDMS film demonstrates astonishing thermostability by maintaining almost consistent room temperature PL intensities after continuous heating-cooling cycles between 200 and 25 °C, which would greatly improve its processability during potential industrial manufacturing. The fabricated LCD backlit based on SCP@MSNs covers 124% of NTSC standard and 95.6% of Rec. 2020 standard, indicating its great potential in practical display field.

Perovskite Quantum Dots with Ultrahigh Solid-State Photoluminescence Quantum Efficiency, Superior Stability, and Uncompromised Electrical Conductivity.

All-inorganic perovskite quantum dots (PQDs), potentially applicable to high-performance display technologies, are facing challenges when the superior luminescence properties with high stability and uncompromised electrical conductivity are combined. Here, by introducing hexylamine sulfate and reducing the reaction rate, we managed to optimize the surface sacrificial coating of CsPbBr3 QDs. As a result, the colloidal PQDs show a photoluminescence quantum efficiency (PLQE) of 95.8% in solution, and an internal PLQE as high as 97.8% in solid-state films. As far as stability is concerned, the PQDs not only show excellent resistance to polar solvent but also can retain over 84% of the initial PL intensity after continuous heating at 100 °C for 60 min. More importantly, the superior stability is achieved without compromising electrical conductivity. The light-emitting diodes made from these PQDs show a current efficiency of 8.9 cd A-1 with excellent thermal stability.

A Sb2S3 Nanoflower/MXene Composite as an Anode for Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) are prospective for energy storage systems owing to their low price and high operating voltage. Antimony-based electrode materials have the advantage of high capacity for PIBs, while suffering from huge volume expansion and inferior stability because of the large radius of K+. Therefore, developing suitable antimony-based electrode materials with high performance is highly challenging. Herein, self-assembled Sb2S3 nanoflowers on the surfaces of MXene (Ti3C2) flakes are synthesized through a solvothermal reaction along with a calcination method. The highly conductive two-dimensional Ti3C2 soft substrate could not only boost the charge transfer kinetics but also buffer the volumetric expansion of Sb2S3 effectively. In addition, the structural stability is enhanced because the Sb2S3 nanoflowers are in situ grown on Ti3C2 flakes through the strong interfacial coupling. Consequently, the Ti3C2-Sb2S3 anode exhibits a high reversible capacity of 461 mAh g-1 at 100 mA g-1, long cycling life (capacity retention of 79% for 500 cycles), and superior rate performance (102 at 2000 mA g-1). This work may provide a pathway for designing advanced materials for PIBs.

Organic phosphomolybdate: a high capacity cathode for potassium ion batteries.

Homogeneous tetra-n-butylammonium phosphomolybdate (TBAPM) nanoparticles with an inter-connected structure were synthesized via a facile soft chemical route and firstly introduced into potassium ion batteries. The obtained novel TBAPM cathode delivers a high capacity of 232 mA h g-1 at 20 mA g-1 and shows slight decay during the subsequent cycle.