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Epitaxial strain has been shown to produce dramatic changes to the orbital structure in transition metal perovskite oxides and, in turn, the rate of oxygen electrocatalysis therein. Here, epitaxial strain is used to investigate the relationship between surface electronic structure and oxygen electrocatalysis in prototypical fuel cell cathode systems. Combining high-temperature electrical-conductivity-relaxation studies and synchrotron-based X-ray absorption spectroscopy studies of La0.5Sr0.5CoO3 and La0.8Sr0.2Co0.2Fe0.8O3 thin films under varying degrees of epitaxial strain reveals a strong correlation between orbital structure and catalysis rates. In both systems, films under biaxial tensile strain simultaneously exhibit the fastest reaction kinetics and lowest electron occupation in the dz2 orbitals. These results are discussed in the context of broader chemical trends and electronic descriptors are proposed for oxygen electrocatalysis in transition metal perovskite oxides.

Degraded LiCoO2 cathode from retired Li‐ion batteries is urgently required to be recycled in a greener way for economic and environmental considerations. The coarse metallurgy technologies for Li/Co extraction with massive CO2 emission and energy consumption cannot satisfy the requirements of carbon neutralization. Herein, it is proposed that direct regeneration of degraded LiCoO2 cathode could be realized via 9‐fluorenone‐mediated Li supplementation and follow‐up structural restoration. The 9‐fluorenone‐lithium reagent is elaborately selected to compensate for the missing Li+ into lattice with targeted stoichiometry owing to its compatible redox potential of 1.95 V versus Li+/Li, which is located just between the reversible intercalation (3.8 V) and irreversible conversion (1.2 V) potentials of LiCoO2 electrode. Then, thermal energy‐driven structure reorganization enables Li/Co atoms to occupy the right sites, accomplishing desirable structure healing within a short annealing time of 4 h. The regenerated LiCoO2 cathode exhibits comparable Li‐storage capability to commercial LiCoO2, benefiting from the non‐destructive direct regeneration technology. In addition, the regeneration route is regarded as environmentally (0.13 kg CO2 kg−1 cell) and economically (10.07 $ kg−1 cell) superior to conventional recycling routes based on life‐cycle analysis. The precise surgery on spent LiCoO2 cathode provides a promising solution for the forthcoming retirement rush of Li‐ion batteries. [ABSTRACT FROM AUTHOR]

The ternary strategy has proven to be an effective method for improving the efficiency of organic solar cells (OSCs). However, designing and selecting the third component still pose challenges. In this study, this issue is addressed by focusing on the PBDB‐T:Y18‐F binary system and introducing a new, strong luminescent, asymmetric small‐molecule acceptor (SMA) called L8‐CBIC‐Cl, which shares a similar skeleton with Y18‐F. The similarity in molecular framework facilitates good compatibility between the two acceptors, resulting in the formation of an alloy‐like acceptor phase. Furthermore, the norbornenyl‐modified end group in L8‐CBIC‐Cl contributes to its strong luminescent properties, which in turn leads to a low non‐radiative energy loss and a high open‐circuit voltage. Consequently, the PBDB‐T:L8‐CBIC‐Cl:Y18‐F based ternary devices realize a high power conversion efficiency (PCE) up to 17.01%, which is higher than PBDB‐T:Y18‐F device (14.49%). Importantly, L8‐CBIC‐Cl exhibits a good universality as a guest acceptor in other three binary systems (D18:Y6, D18:BTP‐eC9‐4F, and D18:L8‐BO). The D18:L8‐BO:L8‐CBIC‐Cl device shows an impressive efficiency of 19%. The work demonstrates that employing SMA with a high PLQY and better miscibility with host acceptor as the third component has a great potential for developing high‐efficiency ternary OSCs. [ABSTRACT FROM AUTHOR]

The discovery of ductile Ag2(S, Se, Te) materials opens a new avenue toward high‐performance flexible/hetero‐shaped thermoelectrics. Specifically, the cubic‐structured materials are quite attractive by combining remarkable plasticity, decent thermoelectric figure of merit (zT), and no phase transition above room temperature. However, such materials are quite few and the understanding is inadequate on their mechanical and thermoelectric properties. Enlightened by the high‐entropy principles, a series of pseudo‐ternary Ag2S‐Ag2Se‐Ag2Te alloys is designed and comprehensive diagrams of composition‐structure‐plasticity‐zT are compiled. Subsequently, the compositional region for the cubic phase is outlined. As a high‐entropy example featuring with anion‐site alloying and disordered Ag ions, Ag2‐xS1/3Se1/3Te1/3 materials exhibit impressively large elongations of 60–97%, ultralow lattice thermal conductivities of ≈0.2 W m−1 K−1, and decent zT values of 0.45 at 300 K, 0.8 at 460 K. The materials can be readily rolled into thin foils, showing excellent flexibility. Finally, a six‐leg in‐plane device is fabricated, achieving an output voltage of 13.6 mV, a maximal power of 12.8 µW, and a power density of 14.3 W m−2 under the temperature difference of 30 K, much higher than the organic counterparts. This study largely enriches the members of cubic ductile inorganic materials for the applications in flexible and hetero‐shaped energy and electronic devices. [ABSTRACT FROM AUTHOR]

LaTiO2N is a promising narrow‐bandgap semiconductor photocatalyst that shows great promise for water redox reactions. However, its performance is often hindered by fast photocarrier recombination events. Herein, LaTiO2N mesoporous single crystals (MSCs) are successfully fabricated via a topotactic conversion route by using the Ruddlesden–Popper compound NaLaTiO4 as the precursor. The LaTiO2N MSCs are characterized by high crystallinity, abundant mesopores, no grain boundaries (GBs), and exposure of (010) and (101) crystal facets. A facet‐assisted photocarrier separation mechanism is identified for these LaTiO2N MSCs which contributes to the much better photocarrier separation than conventional counterparts. By loading proper cocatalysts, LaTiO2N MSCs serve as an efficient photocatalyst for water‐splitting half‐reactions and are capable of photocatalyzing overall water‐splitting reactions, delivering an impressive apparent quantum efficiency (AQE) as high as 65.07% at 420 ± 20 nm for O2‐evolution and a solar‐to‐hydrogen (STH) efficiency as high as 0.012% for solar‐driven overall water splitting. These findings not only highlight the grain‐boundary‐free MSCs with peculiar crystal‐facet exposure as highly active photocatalysts for particulate photocatalysis but also provide a rational design approach for developing efficient photocatalysts. [ABSTRACT FROM AUTHOR]

Urea electrolysis can convert urea from urea‐rich wastewater to hydrogen for environmental protection and sustainable energy production. However, the sluggish kinetics of urea oxidation reaction (UOR) requires valence‐variable sites that are generally active at high anodic overpotentials. Herein, a robust ceramic coating is constructed with coupled tungsten nitride (WN)/nickel carbide (Ni3C) nanoparticles to achieve valence‐stable catalytic sites with outstanding UOR performance. Various characterization results indicate strong interfacial electron transfer from WN to Ni3C in coupled nanoparticles, which enables reservation of Ni2+ sites without self‐oxidation during UOR, quite distinct from the kinetically slow Ni3+OOH‐catalyzed UOR pathway. Theoretical calculations show that the coupled effect in WN/Ni3C leads to enhanced electron transfer from catalytic sites to adsorbed urea, and W sites are thermodynamically favorable for UOR. This efficiently lowers the barrier of rate‐determining step (RDS: *CO‐N2 → *CO·OH), thus enabling fast UOR kinetics and a low potential of 1.336 V at 100 mA cm−2, which identifies this ceramic coating as one of the best UOR electrocatalysts. This work opens a new avenue for design of stable and active sites in ceramics coatings toward advanced electrocatalytic applications. [ABSTRACT FROM AUTHOR]

Flow batteries (FBs) are one of the most promising strategies for large‐scale energy storage, in which the flow rates of electrolytes are critical to the redox reaction efficiency. However, low‐power and energy‐efficient strategies to effectively monitor and adjust the flow rates of FBs are great challenges. Here, a liquid metal based thin‐film and self‐powered triboelectric sensor (LM‐TS) to monitor and adjust the real‐time electrolyte flow rates in FBs is developed. By integrating the LM‐TS with a peristaltic pump (flow rate control unit in FB), the flow rates of electrolytes can be converted into readable electrical output signals. Furthermore, a logical and a control module are adopted to adjust the flow rates of electrolytes automatically after receiving those electrical signals, which are available to guarantee the optimal working condition of FBs. Benefiting from the high conductivity and outstanding ductility of ultrathin LM film, the self‐powered LM‐TS is endowed with high sensitivity, short response time (9.1 ms), and remarkable cyclic stability (> 20000 cycles) without affecting the normal operation of FBs. This is the first prototype of self‐powered adjustment sensor for FBs, which is readily extended to scaled‐up FB equipment for intermediate trial and large‐scale energy‐storage demonstration. [ABSTRACT FROM AUTHOR]

To implement the growing requirement for higher energy density all‐solid‐state lithium batteries (ASSLBs), further increasing the working voltage of LiCoO2 (LCO) is a key to breaking through the bottleneck. However, LiCoO2 severe structural degradation and side reactions at the cathode interface obstruct the development of high‐voltage sulfide‐based ASSLBs (≥4.5 V). Herein, a nano‐metric Li1.175Nb0.645Ti0.4O3 (LNTO) coated LCO cathode where microscopic Ti and Nb segregation at the interface during cycling potentially stabilizes the cathode lattice, and minimizes side reactions, simultaneously, is designed. Advanced transmission electron microscopy reveals that the stable spinel phase minimizes the micro stress at the cathode interface, avoids structure fragmentation, and hence significantly enhances the long‐term cyclic stability of LNTO@LCO @ 4.5 V. Moreover, the differential phase contrast scanning transmission electron microscopy (DPC‐STEM) visualizes the nano‐interlayer LNTO to boost Li+ migration at the cathode interface. Electrochemical impedance spectroscopy (EIS) reveals that sulfide‐based cells with the LNTO nano‐layer effectively reduce the interfacial resistance to 140 Ω compared to LiNbO3 (235 Ω) over 100 cycles. Therefore, 4.5 V sulfide‐based ASSLBs offer gratifying long‐cycle stability (0.5 C for 1000 cycles, 88.6%), better specific capacity, and rate performance (179.8 mAh g–1 at 0.1 C, 97 mAh g–1 at 2 C). [ABSTRACT FROM AUTHOR]

Transition metal chalcogenides are a promising and extremely pivotal class of electrocatalysts with potential applications in alkaline hydrogen evolution reaction (HER), especially, molybdenum diselenide. Although the exposed edge sites are generally considered to be the active sites of MoSe2 for HER, an intrinsic behavior (surface species evolution, structure/morphology conversion, stability) of MoSe2 electrode itself was not unveiled. Herein, the origin of MoSe2‐electrocatalyzed HER activity monitored by the quasi‐operando XPS and in situ Raman spectroscopy is presented. The findings clearly show dynamic evolution of both Mo and Se species on MoSe2 electrode surface for promoting HER activity and maintaining long‐term catalytic stability and reveal an electro‐oxidative dissolution and re‐adsorption mechanism. Theoretical calculations also corroborate these results. As expected, the addition of single or mixed MoO42− and SeO32− to the electrolyte of nickel foam directly verifies the critical role of surface‐adsorbed Mo and Se species for boosting HER activity and stability. Additionally, the oxidative dissolution of Se on NixSey electrode surface during HER is also observed, revealing the universality of oxidative dissolution of Se in transition metal selenides. This study provides a unique insight into the species evolution and surface structure transformation mechanism and activity improved origin of materials during the electroreduction process. [ABSTRACT FROM AUTHOR]

The aggravating extreme climate changes and natural disasters stimulate the exploration of low‐carbon/zero‐carbon alternatives to traditional carbon‐based fossil fuels. Solar‐to‐hydrogen (STH) transformation is considered as appealing route to convert renewable solar energy into carbon‐free hydrogen. Restricted by the low efficiency and high cost of noble metal cocatalysts, high‐performance and cost‐effective photocatalysts are required to realize the realistic STH transformation. Herein, the 2D FePS3 (FPS) nanosheets anchored with TiO2 nanoparticles (TiO2/FePS3) are synthesized and tested for the photocatalytic hydrogen evolution reaction. With the integration of FPS, the photocatalytic H2‐evolution rate on TiO2/FePS3 is radically increased by ≈1686%, much faster than that of TiO2 alone. The origin of the greatly raised activity is revealed by theoretical calculations and various advanced characterizations, such as transient‐state photoluminescence spectroscopy/surface photovoltage spectroscopy, in situ atomic force microscopy combined with Kelvin probe force microscopy (AFM‐KPFM), in situ X‐ray photoelectron spectroscopy (XPS), and synchrotron‐based X‐ray absorption near edge structure. Especially, the in situ AFM‐KPFM and in situ XPS together confirm the electron transport pathway in TiO2/FePS3 with light illumination, unveiling the efficient separation/transfer of charge carrier in TiO2/FePS3 step‐scheme heterojunction. This work sheds light on designing and fabricating novel 2D material‐based S‐scheme heterojunctions in photocatalysis. [ABSTRACT FROM AUTHOR]