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Transition metal (TM) substitution has been widely applied to change complex oxides crystal structures to create high energy density electrodes materials in high performance rechargeable lithium-ion batteries. The complex local structure in the oxides imparted by the TM arrangement often impacts their electrochemical behaviors by influencing the diffusion and intercalation of lithium. Here, a major discrepancy is demonstrated between the global and local structures of the promising high energy density and high voltage LiNi0.5Mn1.5O4 spinel cathode material that contradicts the existing structural models. A new single-phase lattice-cell orientation disorder model is proposed as the mechanism for the local ordering that explains how the inhomogeneous local distortions and the coherent connection give rise to the global structure in the complex oxide. Further, the single-phase model is consistent with the electrochemical behavior observation of the materials. [ABSTRACT FROM AUTHOR]

Neutron diffraction under operando battery cycling is used to study the lithium and oxygen dynamics of high Li-rich Li(Lix/3 Ni(3/8-3x/8) Co(1/4-x/4) Mn(3/8+7x/24) O2) x = 0.6, HLR) and low Li-rich Li(Lix/3 Ni(1/3-x/3) Co(1/3-x/3) Mn(1/3+x/3) O2 (x = 0.24, LLR) compounds that exhibit different degrees of oxygen activation at high voltage. The measured lattice parameter changes and oxygen position show largely contrasting changes for the two cathodes where the LLR exhibits larger movement of oxygen and lattice contractions in comparison to the HLR that maintains relatively constant lattice parameters and oxygen position during the high voltage plateau until the end of charge. Density functional theory calculations show the presence of oxygen vacancy during the high voltage plateau; changes in the lattice parameters and oxygen position are consistent with experimental observations. Lithium migration kinetics for the Li-rich material is observed under operando conditions for the first time to reveal the rate of lithium extraction from the lithium layer, and transition metal layer is related to the different charge and discharge characteristics. At the beginning of charging, the lithium extraction predominately occurs within the lithium layer. Once the high voltage plateau is reached, the lithium extraction from the lithium layer slows down and extraction from the transition metal layer evolves at a faster rate. [ABSTRACT FROM AUTHOR]

Solid-oxide fuel cells are an attractive energy conversion technology for clean electric power production. To render them more affordable, discovery of new cathode materials with high reactivity to oxygen reduction reaction (ORR) at temperatures below 700 °C is needed. Recent studies have demonstrated that La0.8Sr0.2CoO3/(La0.5Sr0.5)2CoO4 (LSC113/214) hetero-interfaces exhibit orders of magnitude faster ORR kinetics compared with either single phase at 500 °C. To obtain a microscopic level understanding and control of such unusual enhancement, we implemented a novel combination of in situ scanning tunneling spectroscopy and focused ion beam milling to probe the local electronic structure at nanometer resolution in model multilayer superlattices. At 200-300 °C, the LSC214 layers are electronically activated through an interfacial coupling with LSC113. Such electronic activation is expected to facilitate charge transfer to oxygen, and concurrent with the anisotropically fast oxygen incorporation on LSC214, quantitatively explains the vastly accelerated ORR kinetics near the LSC113/214 interface. Our results contribute to an improved understanding of oxide hetero-interfaces at elevated temperatures and identify electronically coupled oxide structures as the basis of novel cathodes with exceptional performance. [ABSTRACT FROM AUTHOR]

Highlights from the article: Keywords: high energy density; Na3V2(PO4)3; redox flow batteries; redox-targeting; sodium batteries In article number 1901188, Yong-Sheng Hu, Qing Wang and co-workers report a flow battery based on the redox-targeting reactions of methylphenothiazine and fluorenone with Na SB 3 sb V SB 2 sb (PO SB 4 sb ) SB 3 sb as the sole capacity booster in both cathodic and anodic compartments. High energy density, redox flow batteries, sodium batteries, Na3V2(PO4)3, redox-targeting.

Redox flow batteries have considerable advantages of system scalability and operation flexibility over other battery technologies, which makes them promising for large‐scale energy storage application. However, they suffer from low energy density and consequently relatively high cost for a nominal energy output. Redox targeting–based flow batteries are employed by incorporating solid energy storage materials in the tank and present energy density far beyond the solubility limit of the electrolytes. The success of this concept relies on paring suitable redox mediators with solid materials for facilitated reaction kinetics and lean electrolyte composition. Here, a redox targeting‐based flow battery system using the NASICON‐type Na3V2(PO4)3 as a capacity booster for both the catholyte and anolyte is reported. With 10‐methylphenothiazine as the cathodic redox mediator and 9‐fluorenone as anodic redox mediator, an all‐organic single molecule redox targeting–based flow battery is developed. The anodic and cathodic capacity are 3 and 17 times higher than the solubility limit of respective electrolyte, with which a full cell can achieve an energy density up to 88 Wh L−1. The reaction mechanism is scrutinized by operando and in‐situ X‐ray and UV–vis absorption spectroscopy. The reaction kinetics are analysed in terms of Butler–Volmer formalism. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen evolution from natural seawater faces the severe challenges of abundant salts, which adsorb on the active sites and result in undesirable side reactions and photocatalyst poisoning. Herein, a series of main‐chain‐engineered discontinuously conjugated polymer (DCP) photocatalysts is presented with bifunctional crown ether (CE) structures for hydrogen evolution from seawater. The hydrophilic CE can significantly inhibit the aggregation of DCPs induced by salts. Meanwhile, cyclic CE can effectively adsorb cations to uncover the active sites to increase their interaction with protons, which can increase the hydrogen evolution rates and significantly reduce the efficiency roll‐off in natural seawater. Through atomistic studies, the formation of hydrogen bonds with bifunctional CE is elucidated and further analysis of the microscale mechanisms is also conducted using molecular dynamics and ab initio techniques. This work suggests that CE‐based polymer has the potential to enhance its ability to produce hydrogen through photocatalysis using seawater. [ABSTRACT FROM AUTHOR]

Transition metal arrangement impacts electrochemical behaviors of high‐voltage electrodes for Li‐ion batteries. In article number 1601950, Ke An and co‐workers report a new lattice‐cell orientation disorder model as the local ordering mechanism, which explains the difference between global and local structures of LiNi0.5Mn1.5O4. The cover picture shows an arrangement of the unit cells by color with different orientations. [ABSTRACT FROM AUTHOR]

High current density hydrogen evolution reaction (HER) in alkaline water electrolysis plays crucial role in renewable and sustainable energy systems, while posing a great challenge to the highly‐efficient electrocatalysts. Here, the synthesis of Ni/NiO@MoO3−x composite nanoarrays is reported by a moderate reduction strategy, combining Ni/NiO nanoparticles (≈20 nm) with amorphous MoO3−x nanoarrays. The Ni/NiO@MoO3−x composite nanoarrays possess enhanced hydrophilicity, optimize reaction energy barriers, accelerate reactant diffusion/bubble detachment, and therefore display an ultrahigh alkaline HER activity with a low η10 overpotential of 7 mV as well as Tafel slope of 34 mV dec−1. More significantly, the Ni/NiO@MoO3−x nanoarrays only demand low overpotentials of 75 and 112 mV to deliver 100 and 200 mA cm−2 hydrogen production current, and can steadily work at 100 mA cm−2 for 40 h, which is more efficient and stable than the Pt/C catalyst. [ABSTRACT FROM AUTHOR]

New anthracene‐bridged organic dyes CXC12 and CXC22 are designed and synthesized for high‐efficiency dye‐sensitized solar cells (DSSCs) under dim light. Compared to their parent dye TY6, CXC dyes have additional anthracene‐acetylene group to extend the π‐conjugation of the molecules, resulting in red‐shifted absorption and an enhanced molar extinction coefficient. The absorption spectra of CXC12 and CXC22 with a maximum located at 561 and 487 nm, respectively, match to those of AM 1.5G sunlight and T5 fluorescent light better than that of TY6 (419 nm). It was initially anticipated that long alkoxyl chains introduced to the 2,6‐position of the bridged anthracenyl in CXC12 will retard charge recombination and dye molecular aggregation, and achieve a higher device open‐circuit voltage. However, adsorption of CXC12 molecules on the photoanode dramatically decrease to less than half as compared to that of CXC22 and TY6, resulting in lower short‐circuit current and thus power conversion efficiency. Among these three anthracene‐based dyes, CXC22 has the most appropriate molecular structure for light harvesting and striking the balance between dye loading and molecular aggregation, to exhibit a remarkable power conversion efficiency as high as 37.07% under dim‐light. Therefore, this work shows the potential of anthracene‐bridged organic dyes for indoor photovoltaic applications. [ABSTRACT FROM AUTHOR]

A novel combination of scanning tunneling microscopy and focus ion beam milling is developed to probe the local electronic structure near the hetero‐interfaces of oxide superlattices with nanometer‐scale resolution at elevated temperatures and in oxygen gas environment. On page 1221, Bilge Yildiz and co‐workers use this method to reveal the mechanism behind the very high reactivity of the interface between (La,Sr)CoO3 and LaSrCoO4 layers to oxygen reduction at high temperature. The results advance the understanding of oxide hetero‐interfaces at elevated temperatures and identify electronically coupled oxide structures as novel cathodes with exceptional performance for application in solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Synergistic Effect of Crown Ether and Main-Chain Engineering for Boosting Hydrogen Evolution of Polymer Photocatalysts in Seawater (Adv. Keywords: conjugated polymers; crown ether; hydrogen evolution from seawater; hydrogen evolution reaction; main-chain engineering; sodium-ions capture; visible light-driven water splitting EN conjugated polymers crown ether hydrogen evolution from seawater hydrogen evolution reaction main-chain engineering sodium-ions capture visible light-driven water splitting 1 1 1 08/08/23 20230804 NES 230804 B Hydrogen Evolution b In article 2300986, Chin-Wen Chen, Chi-Hua Yu, Ho-Hsiu Chou, and co-workers develop a series of main chain-engineered polymer photocatalysts with bifunctional crown ether (CE) structures for hydrogen evolution from seawater. Conjugated polymers, crown ether, hydrogen evolution from seawater, hydrogen evolution reaction, main-chain engineering, sodium-ions capture, visible light-driven water splitting. [Extracted from the article]

Abstract: Through simultaneously enhancing the power factor by engineering the extra light band and enhancing phonon scatterings by introducing a high density of stacking faults, a record figure‐of‐merit over 2.0 is achieved in p‐type AgSbTe2−xSex alloys. Density functional theory calculations confirm the presence of the light valence band with large degeneracy in AgSbTe2, and that alloying with Se decreases the energy offset between the light valence band and the valence band maximum. Therefore, a significantly enhanced power factor is realized in p‐type AgSbTe2−xSex alloys. In addition, transmission electron microscopy studies indicate the appearance of stacking faults and grain boundaries, which together with grain boundaries and point defects significantly strengthen phonon scatterings, leading to an ultralow thermal conductivity. The synergetic strategy of simultaneously enhancing power factor and strengthening phonon scattering developed in this study opens up a robust pathway to tailor thermoelectric performance. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) based on B CXC22 b exhibit a remarkable power conversion efficiency as high as 37.07% under T5 fluorescent light, making DSSCs a promising indoor photovoltaic technique for the Internet of Things in the near future. Keywords: anthracene; dye-sensitized solar cells; indoor photovoltaics; organic dyes EN anthracene dye-sensitized solar cells indoor photovoltaics organic dyes 1 1 1 05/30/22 20220526 NES 220526 B Dye-Sensitized Solar Cells b In article number 2104051, Tzu-Chien Wei, Chen-Yu Yeh and co-workers develop new anthracene-based organic dyes with a simple molecular structure, showing red-shifted and broadened absorption in the visible region. Anthracene, dye-sensitized solar cells, indoor photovoltaics, organic dyes. [Extracted from the article]