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Atomically dispersed metal‐nitrogen‐carbon catalysts have been extensively explored for various sustainable energy‐related reactions. From a material perspective, these catalysts are likely to consist of a combination of single‐atom, dual‐atom and possibly even multi‐atom sites. However, pinpointing their true active sites has remained a challenging task. In this study, a model catalyst is introduced, Co/CoMn‐NC, featuring both Co single‐atom sites and CoMn dual‐atom sites on a nitrogen‐doped carbon substrate. By employing a combination of X‐ray adsorption spectroscopy and density functional theory calculations, the atomic configuration of Co/CoMn‐NC has been determined. Density functional theory calculations are also used to unequivocally identify Co‐atom within the CoMn dual‐atom motif as the predominate active site of the Co/CoMn‐NC model catalyst toward oxygen reduction reaction (ORR), which is further confirmed by in situ Raman spectroscopy. The cooperative interactions between Co single‐atom sites and CoMn dual‐atom sites can finely tune the d‐band center and ameliorate the adsorption and desorption behaviors of the intermediates, thereby facilitating ORR kinetic. Overall, the study introduces a systematic strategy to elucidate the structure and the superiority of the model system and provides new insights into atomically dispersed multi‐metal active sites, showcasing that enhanced catalytic performance extends beyond unified diatomic sites or monatomic sites. [ABSTRACT FROM AUTHOR]

The electrocaloric effect represents an adiabatic temperature change or isothermal entropy change upon the application or removal of an external electric field. However, the effect of the repetitive bipolar/unipolar electric field on the electrocaloric effect in ferroelectrics is not well understood. In this work, the electrocaloric effect after both bipolar and unipolar electrical cycling in Pb0.92La0.08Zr0.65Ti0.35O3 relaxor thin films has been indirectly evaluated using the Maxwell relationship. It was found that at room temperature, the electrocaloric temperature change ΔT under higher electric fields decreases gradually from a positive value to a negative one with the increase in the bipolar/unipolar fatigue cycle number. Intriguingly, around the Curie temperature, the positive ΔT of the film after bipolar/unipolar cycling was found to decrease under low or intermediate electric fields, while it remains almost unchanged under high electric fields. This behavior is attributed to the pinning effect of defects caused by phase decomposition during both bipolar and unipolar fatigue. Note that the increase in polarization by temperature induced domain depinning close to room temperature after the fatigue process is manifested by using the Maxwell relation indirectly. Our work further reveals the origin of both the electrocaloric effect and ferroelectric electrical fatigue and is important for the applications of practical electrocaloric refrigerators. [ABSTRACT FROM AUTHOR]

(Pb 0.92 La 0.08)(Zr 0.65 Ti 0.35)O 3 (PLZT), PbZrO 3 (PZO) films, and type A and type B PLZT/PZO multilayer thin films were deposited on Pt(111)/TiO x /SiO 2 /Si substrates by sol-gel method, where type A and type B films stand for PLZT/PZO/PLZT/PZO/PLZT/PZO and PLZT/PZO/PLZT/PLZT/PZO/PLZT multilayer thin film, respectively. Compared to the PLZT and PZO film, enhanced breakdown field strength and improved energy storage density were obtained in type A and B multilayer thin films. A superior energy storage density of 29.7 J/cm3 with the energy storage efficiency of 50.8% was achieved in type B multilayer thin film, corresponding to 81% enhancement compared with the energy storage density of PLZT films (16.4 J/cm3). Additionally, the type B multilayer thin film exhibits a good thermal stability up to 160 °C and excellent fatigue endurance after 107 charging-discharging cycles. The enhanced energy storage performance of type B multilayer thin film shows promise and may stimulate further researches on energy storage applications of multilayer dielectric thin films. [ABSTRACT FROM AUTHOR]

• Ca2+ and Sr2+ can increase the stability of antiferroelectric phase while Ba2+ decreases it. • An enhanced negative ECE of Δ T around − 10.6 K was obtained in the Pb 0.9 Sr 0.1 ZrO 3 thin film at room temperature. • The modification of antiferroelectric-ferroelectric phase transition is an effective strategy to enhance the negative electrocaloric effect in antiferroelectric thin films. In the Pb 0.9 Sr 0.1 ZrO 3 thin film, an enhanced negative electrocaloric effect (ECE) has been observed based on the Maxwell relation, with Δ T of around − 10.6 K under 450 kV/cm at room temperature, as compared with the pristine PbZrO 3 thin film (with Δ T of around −7.3 K under 300 kV/cm at 361 K), as shown in the figure. Our work demonstrates that modifying antiferroelectric-ferroelectric phase transition is an effective way to enhance the negative ECE in antiferroelectric thin films. [Display omitted] Electrocaloric effect (ECE) in dielectric materials has attracted much attention due to its promising applications in solid-state cooling devices. In this work, alkaline-earth doped PbZrO 3 antiferroelectric thin films (Pb 0.9 A 0.1 ZrO 3 (A=Ca, Sr, and Ba)) were deposited by a sol-gel method and its antiferroelectric-ferroelectric phase competition as well as the negative ECE were studied. It is found that Ca2+ and Sr2+ expand the antiferroelectric phase region while Ba2+ reduces it, due to the different ion radii of these alkaline-earth elements. As a result, the Pb 0.9 Sr 0.1 ZrO 3 thin film exhibits an enhanced negative ECE with Δ T of around − 10.6 K under 450 kV/cm whereas the Pb 0.9 Ba 0.1 ZrO 3 thin film shows a decreased negative ECE with Δ T of around − 2.5 K under 200 kV/cm, as compared with the pristine PbZrO 3 thin films (with Δ T of around −7.3 K under 300 kV/cm). This work provides an effective method to enhance the negative ECE of antiferroelectrics in electrical cooling applications by adjusting their antiferroelectric to ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

Developing high‐performance anode current collectors with three‐dimensional structure and lithiophilic layers is of great importance to further advance the application of lithium metal batteries. However, relatively few research has focused on the transition of substrate and the intrinsic structure stability after electrodeposition of lithium on substrates, which leads to an incomplete understanding of the behavior of lithium deposition. Herein, a lithium metal anodes host with a highly stable and 3D structure has been effectively produced through in situ development of nanoflake arrays embedded with Co3O4 obtained from ZIF on nickel foams (Co3O4‐NF). And the actual lithium deposition sites and lithium deposition process on Co3O4‐NF are elucidated via a combination of characterization techniques and electrochemical analytical methods. Consequently, the resulting Co3O4‐NF@Li anodes could effectively inhibit lithium dendrite formation and mitigate volume expansion, demonstrating a significantly extended and consistent lifespan of 800 cycles (1600 h) at 1 mA cm−2 with low overpotential and insignificant voltage fluctuation for the process of lithium stripping and plating in symmetric cells. Herein, it is aimed to examine the transitions of metal oxides as a lithiophilic site for the lithium metal anode. It offers novel perspectives and approaches for the design of dendrite‐free lithium metal anodes. [ABSTRACT FROM AUTHOR]

Piezoelectric actuators play an important role in modern electronic devices. In this work, 0.7Bi(1−x)SmxFeO3–0.3BaTiO3 lead-free piezo-ceramics are fabricated through the rapid thermal quenching technique for enhancing the electric-field-induced strain response. All the ceramic samples own a typical perovskite structure, and the morphotropic phase boundary can be achieved after Sm substitution. Additionally, a high TC of 403 °C and excellent ferroelectricity can be obtained at room temperature for the x = 0.03 composition, together with a large peak-to-peak strain value (∆S = 0.5%). Furthermore, a larger strain value ∆S of 0.45% at 150 °C can also be realized in 0.7Bi0.95Sm0.05FeO3–0.3BaTiO3 ceramic. Our results could further stimulate the investigations on lead-free ceramics for piezoelectric actuator applications. [ABSTRACT FROM AUTHOR]

Lead-free (0.70- x)BiFeO 3 -0.30BaTiO 3 - x AgNbO 3 +5‰mol CuO (abbreviated as BF-BT- x AN) ceramics were fabricated using a modified thermal quenching technique. BF-BT- x AN ceramics are of a perovskite structure with morphotropic phase boundary (MPB) and show strong relaxor properties. Remarkably, the high recoverable energy storage density of 2.11 J/cm3 is obtained for BF-BT- x AN with x = 0.14. For the x = 0.14 ceramics, its energy storage efficiency is as high as 84 % at relative low field of 195 kV/cm, together with an outstanding thermal stability in a broad temperature range from 25 °C to 150 °C. In addition, this ceramic maintains superior energy storage performance even after 8 × 104 electrical cycles due to its high densification after doping Ag 2 O and Nb 2 O 5. The result suggests that lead-free BF-BT- x AN ceramics may be promising candidate for dielectric energy storage application. [ABSTRACT FROM AUTHOR]