A high recoverable energy storage density polymer composite film has been designed in which the ferroelectric-paraelectric 0.85 (K_0.5Na_0.5NbO₃)-0.15SrTiO₃ (abbreviated as KNN-ST) solid solution particles were introduced into polyvinylidene fluoride (PVDF) polymer as functional fillers. The effects of the polarization properties of K_0.5Na_0.5NbO₃ (KNN) and KNN-ST particles on the energy storage performances of KNN-ST/PVDF film were systemically studied. And the introduction of SrTiO₃ (ST) was effective in reducing the remnant polarization of the particles, improving the dielectric properties and recoverable energy storage density of the KNN-ST/PVDF films. Compared to KNN/PVDF films, the dielectric permittivity of composite films was enhanced from 17 to 38 upon the introduction of ST. A recoverable energy storage density of 1.34 J/cm³ was achieved, which is 202.60% larger than that of the KNN/PVDF composite films. The interface between the particles and the polymer matrix was considered to the enhanced dielectric permittivity of the films. And the reduced remnant polarization of the composites was regarded as the improving high recoverable energy storage density. The results demonstrated that combing ferroelectric- paraelectric particles with polymers might be a key method for composites with excellent dielectric permittivity, high energy storage density, and energy efficiency.

(Ba _0.85 Ca _0.15 )(Zr _0.1 Ti _0.9−x Ce _x )O ₃ + y Sb ceramics prepared by the conventional solid-state reaction.

High cost and restricted activity of electrocatalysis are the major challenges for hydrogen generation and biosensors. In this work, we provided a one-pot synthesis of Cu_xPd_y alloy nanoparticles (NPs) with controllable atomic ratio and “clean surface”. Benefiting from the preferable d-band structure, the Cu₆₂Pd₃₈ NPs exhibited a lower overpotentials in the hydrogen evolution reaction (HER) over the full pH range. In the acidic media, Cu₆₂Pd₃₈ NPs achieved a low overpotential of 28.12 mV for HER, which was 25.73% of Pd NPs. In the neutral solution, the overpotential by Cu₆₂Pd₃₈ NPs is only 41.71% for that by uncleaned CuPd NPs. In alkaline media, the overpotential by Cu₆₂Pd₃₈ NPs was declined from 38.01 to 20.20 mV after 720 min yielding hydrogen, which was only 53.14% for the initial overpotential. As applied in biosensor, the synergistic effect of Cu and Pd accelerated the kinetics of electrocatalytic process, resulting in an enhanced performance. The glucose sensor constructed by Cu₆₇Pd₃₃ exhibited a wider detection range up to 100.0 mM. And the sensitivity is 379.4 µA/(mM·cm²), which is ca. 4.63 and 14.09 folds for that by pure Cu NPs and Pd NPs, respectively. An optimal atomic percent would be conducive to optimize electrocatalytic activity of Cu_xPd_y alloy. The volcano plots for Cu_xPd_y would open up a new avenue for designing electrocatalysis with rationalized cost and optimized performance.