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The critical role of the pyrolysis temperature for ZIF-derived ORR catalysts is revealed by in situ TEM in detail. A facile low temperature strategy is inspired to achieve an outstanding ORR performance.

In this paper, (Bi0.5Na0.5)0.94Ba0.06Ti1-xZnxO3 ceramics (0 ≤ x ≤ 0.06) were prepared by the solid oxide reaction route. The doping of Zn2+ into Bi0.5Na0.5TiO3-6BaTiO3 delays the crossover from nonergodic to ergodic states, and the thermal depolarization temperature Td is delayed from 85 °C for pure samples to 120 °C for samples doped by 6% Zn2+, as confirmed by temperature-dependent dielectric and ferroelectric measurements. It suggests that the variation of the Td could be ascribed to the reformation of the long-range ferroelectric order due to the large ionic polarizability of Zn2+. The high ionic polarizability of Zn2+ can result in a large dipole moment of BO6 octahedra, thus strengthening the coherence of neighboring dipoles and suppressing the ferroelectric–relaxor transition. These results improve our understanding on the thermal depolarization of Bi0.5Na0.5TiO3-based ferroelectrics.

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NiO films with amorphous and crystalline structure are prepared via sol-gel method. The electrochromic performances are evaluated in a KOH electrolyte by cyclic voltammetry (CV), which demonstrates that the crystalline NiO thin film has excellent stability and durability compared with the amorphous film. Meanwhile, the unique method of multi-cycle double-step potential chronocoulometry (MDPC) is firstly employed to analyze the electrochromic performance of the NiO films. It shows that the cyclic tendency obtained from MDPC is consistent with the CV evolutions. The relationship between charge densities and cycles can be directly obtained by MDPC, consequently, the reversibility of films can be directly evaluated by the ratio of the extracted/inserted charges. As a primary advantage, the response charges obtained by MDPC technique can be divided into three parts including Faradic charges (Q f ) associated with redox activity leading to chromic change, the capacitive charges (Q dl ) corresponding to charging and discharging of electrodeelectrolyte double-layer capacitor, and parasitic charges (Q ads ) consumed by electrolysis of adsorbed species. The electrochromic mechanism of NiO films are further explored by analyzing the cycle dependence of Q f and Q ads evolutions. It adequately supports that MDPC has significant advantage to analyze the electrochromic performance and mechanism of electrochromic materials.

In this paper, we demonstrate that the double‐step chronoamperometry and chronocoulometry techniques are efficient tools for characterizing the basic electrochromic performance of WO3 films (i. e., coloration/bleaching conversion, charge capacity and coloration efficiency). In combination with in situ spectroelectrochemical study, the variations in the optical modulation and charge capacity of the WO3 film under different potential windows were attributed to different ion diffusion depths and the quantity of WO3 sites participating in the redox reaction. Moreover, the double‐step techniques have distinctive advantages for analyzing the cyclic mechanism of the WO3 film. When the inserted Li+ ions in the coloration process cannot be completely extracted from the film in the next bleaching process, these ions accumulate in the film upon cycling, leading to the degradation of the electrochromic performance. Here the accumulated ions are referred to as “unrecoverable ions”. The abundant formation of unrecoverable ions may be due to incomplete reduction of a portion of LixWO3, which is caused by collapse of the Li+ ion diffusion channels in the deep of film after repeated cycles. All these results support that the double‐step chronoamperometry and chronocoulometry techniques have significant advantages to analyze the cyclic stability and explore the degradation mechanism of electrochromic WO3 films.

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