Layered α-Ni(OH) and its derivative bimetallic hydroxides (e.g., α-(Ni/Co)(OH)) have attracted much attention due to their high specific capacitance, although their insufficient cycling stability has blocked their wide application in various technologies. In this work, we demonstrate that the cycling performance of α-(Ni/Co)(OH) can be obviously enhanced via the intrinsic pillar effect of metaborate. Combining the high porosity feature of the metaborate stabilized α-(Ni/Co)(OH) and the improved electronic conductivity offered by graphene substrate, the average capacitance fading rate of the metaborate stabilized α-(Ni/Co)(OH) is only ∼0.0017% per cycle within 10 000 cycles at the current density of 5 A g. The rate performance is excellent over a wide temperature range from -20 to 40 °C. We believe that the enhancements should mainly be ascribed to the excellent structural stability offered by the metaborate pillars, and the detailed mechanism is discussed.

Single-metal site catalysts have exhibited highly efficient electrocatalytic properties due to their unique coordination environments and adjustable local structures for reactant adsorption and electron transfer. They have been widely studied for many electrochemical reactions, including oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, it remains a significant challenge to realize high-efficiency bifunctional catalysis (ORR/OER) with single-metal-type active sites. Herein, we report atomically dispersed Fe–Co dual metal sites (FeCo–NC) derived from Fe and Co co-doped zeolitic imidazolate frameworks (ZIF-8s), aiming to build up multiple active sites for bifunctional ORR/OER catalysts. The atomically dispersed FeCo–NC catalyst shows excellent bifunctional catalytic activity in alkaline media for the ORR (E 1/2 = 0.877 V) and the OER (E j=10 = 1.579 V). Moreover, its outstanding stability during the ORR and the OER is comparable to noble-metal catalysts (Pt/C and RuO2). The atomic dispersion state, coordination structure, and the charge density difference of the dual metal site FeCo–NC were characterized and determined using advanced physical characterization and density functional theory (DFT) calculations. The FeCo–N6 moieties are likely the main active sites simultaneously for the ORR and the OER with improved performance relative to the traditional single Fe and Co site catalysts. We further incorporated the FeCo–NC catalyst into an air electrode for fabricating rechargeable and flexible Zn–air batteries, generating a superior power density (372 mW cm–2) and long-cycle (over 190 h) stability. This work would provide a method to design and synthesize atomically dispersed multi-metal site catalysts for advanced electrocatalysis.

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Background: Little empirical evidence is known about the sleep quality of frontline health professionals working in isolation units or hospitals during the novel coronavirus disease (COVID-19) outbreak in China. This study thus aimed to examine the prevalence of poor sleep quality and its demographic and correlates among frontline health professionals.Methods: This is a multicenter, cross-sectional survey conducted in Liaoning province, China. Sleep quality was measured by the Pittsburgh Sleep Quality Index (PSQI).Results: A total of 1,931 frontline health professionals were recruited. The prevalence of poor sleep quality was 18.4% (95%CI: 16.6%-20.11%). Multivariate logistic regression analysis found that older age (OR=1.043, 95%CI=1.026-1.061, P < 0.001), being nurse (OR=3.132, 95%CI=1.727-5.681, P < 0.001), and working in outer emergency medical team (OR=1.755, 95%CI=1.029-3.064, P=0.039) were positively associated with poor sleep quality. Participants who were familiar with crisis response knowledge were negatively associated with poor sleep quality (OR=0.70, 95%CI=0.516-0.949, P=0.021). Conclusion:The prevalence of poor sleep quality was relatively low among frontline health professionals during the COVID-19 epidemic. Considering the negative impact of poor sleep quality on health professionals' health outcomes and patient outcomes, regularly screening and timely treatments are warranted to reduce the likelihood of poor sleep quality in health professionals.

The abundant reserve and low price of potassium resources promote K-ion batteries (KIBs) becoming a promising alternative to Li-ion batteries, while the large ionic radius of K-ions creates a formidable challenge for developing suitable electrodes. Here Ni-substituted Prussian blue analogues (PBAs) are investigated comprehensively as cathodes for KIBs. The synthesized K1.90Ni0.5Fe0.5­[Fe­(CN)6]0.89·0.42H2O (KNFHCF-1/2) takes advantage of the merits of high capacity from electrochemically active Fe-ions, outstanding electrochemical kinetics induced by decreased band gap and K-ion diffusion activation energy, and admirable structure stability from inert Ni-ions. Therefore, a high first capacity of 81.6 mAh·g–1 at 10 mA·g–1, an excellent rate property (53.4 mAh·g–1 at 500 mA·g–1), and a long-term lifespan over 1000 cycles with the lowest fading rate of 0.0177% per cycle at 100 mA·g–1 can be achieved for KNFHCF-1/2. The K-ion intercalation/deintercalation proceeds through a facile solid solution mechanism, allowing 1.5-electron transfer based on low- and high-spins FeII/FeIII couples, which is verified by ex situ XRD, XPS, and DFT calculations. The K-ion full battery is also demonstrated using a graphite anode with a high energy density of 282.7 Wh·kg–1. This work may promote more studies on PBA electrodes and accelerate the development of KIBs.