The electrochemical nitrogen reduction reaction (NRR) is a promising energy-efficient and low-emission alternative to the traditional Haber-Bosch process. Usually, the competing hydrogen evolution reaction (HER) and the reaction barrier of ambient electrochemical NRR are significant challenges, making a simultaneous high NH 3 formation rate and high Faradic efficiency (FE) difficult. To give effective NRR electrocatalysis and suppressed HER, the surface atomic structure of W 18 O 49 , which has exposed active W sites and weak binding for H 2 , is doped with Fe. A high NH 3 formation rate of 24.7 mg h À1 mg cat À1 and a high FE of 20.0 % are achieved at an overpotential of only À0.15 V versus the reversible hydrogen electrode. Ab initio calculations reveal an intercalation-type doping of Fe atoms in the tunnels of the W 18 O 49 crystal structure, which increases the oxygen vacancies and exposes more W active sites, optimizes the nitrogen adsorption energy, and facilitates the electrocatalytic NRR.

BackgroundChildhood obesity has been a serious public health problem. An effective school-based physical activity (PA) intervention is still lacking in China. This study aimed to assess the effectiveness of a school-based physical activity intervention during 12 weeks on obesity and related health outcomes in school children.MethodsIt was a non-randomized controlled trial. Altogether 921 children aged 7 to 15 years were recruited at baseline survey. Children in the intervention group (n = 388) participated in a multi-component physical activity intervention during 12 weeks that included improvement of physical education, extracurricular physical activities for overweight/obese students, physical activities at home, and health education lectures for students and parents. Children (n = 533) in the control group participated in usual practice.ResultsParticipants had mean age of 10.4 years, mean body mass index (BMI) of 19.59 kg/m2, and 36.8 % of them were overweight or obese at baseline survey. The change in BMI in intervention group (−0.02 ± 0.06 kg/m2) was significantly different from that in control group (0.41 ± 0.08 kg/m2). The adjusted mean difference was −0.43 kg/m2 (95% CI: −0.63 to −0.23 kg/m2, P < 0.001). The effects on triceps, subscapular, abdominal skinfold thickness and fasting glucose were also significant in intervention group compared with control group (all P < 0.05). The change in duration of moderate to vigorous physical activity (MVPA) in intervention group (8.9 ± 4.3 min/day) was significantly different from that in control group (−13.8 ± 3.3 min/day). The adjusted mean difference was 22.7 min/day (95% CI: 12.2 to 33.2 min/day, P < 0.001).ConclusionsThe school-based, multi-component physical activity intervention was effective to decreasing levels of BMI, skinfold thickness, fasting glucose and increasing duration of MVPA. These findings provided evidence for the development of effective and feasible school-based obesity interventions.Trial registrationClinicaltrials.gov Identifier: NCT02074332 (2014-02-26)

A yolk-shell-structured carbon@void@silicon (CVS) anode material in which a void space is created between the inside silicon nanoparticle and the outer carbon shell is considered as a promising candidate for Li-ion cells. Untill now, all the previous yolk-shell composites were fabricated through a templating method, wherein the SiO2 layer acts as a sacrificial layer and creates a void by a selective etching method using toxic hydrofluoric acid. However, this method is complex and toxic. Here, a green and facile synthesis of granadillalike outer carbon coating encapsulated silicon/carbon microspheres which are composed of interconnected carbon framework supported CVS nanobeads is reported. The silicon granadillas are prepared via a modified templating method in which calcium carbonate was selected as a sacrificial layer and acetylene as a carbon precursor. Therefore, the void space inside and among these CVS nanobeads can be formed by removing CaCO3 with diluted hydrochloric acid. As prepared, silicon granadillas having 30% silicon content deliver a reversible capacity of around 1100 mAh g−1 at a current density of 250 mA g−1 after 200 cycles. Besides, this composite exhibits an excellent rate performance of about 830 and 700 mAh g−1 at the current densities of 1000 and 2000 mA g−1, respectively. (≈4200 mAh g −1 ), relatively low discharge potential (≈0.5V vs Li/Li + ), abundance, and environmental benignity. [1][2][3][4][5][6] However, the dramatic volume change (>300%) during lithiation and delithiation processes leads to severe pulverization and continual formation of solid electrolyte interphase (SEI) on the newly formed silicon surfaces, resulting in a large capacity loss. [7][8][9][10][11] Therefore, the cycling performance of silicon-based anodes is still far from satisfactory from a commercial point of view. [ 12 ] Silicon nanoparticles (Si NPs) have been found to tolerate extreme changes in volume with cycling. [ 13 ] Hence, great efforts have been made to improve the cycling stability and electrical conductivity by using various Si-based nanostructures, including Si nanowires, [ 3,14,15 ] porous Si, [16][17][18][19] and conductive agent coated Si such as carbon, [ 18,20,21 ] Ag, [ 22,23 ] and conducting polymer. [ 24 ] Among them, a yolkshell-structured carbon@void@silicon (CVS) composite [ 25,26 ] is quite promising for practical applications, because the void space between the outer carbon shell and the inside Si NP allows the room for volume changes of Si NP without deforming the carbon shell and SEI fi lm, which in turn allows for the growth of a stable SEI on the surface of the outer carbon shell. [ 26 ] Besides, the homogeneous carbon coating shell can prevent the electrolyte ingress and the direct contact of Si NPs with the electrolyte, so the SEI will only be formed on the outer surface of the carbon shell, leading to the high Coulombic effi ciency and improved cycling stability. [ 25 ] For instance, Cui and co-workers achieved a high capacity of ≈2800 mAh g −1 with a very good cycling s...

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The electrochemical mechanism of nanocrystalline silicon anode in sodium ion batteries is first studied via in operando Raman and in operando X‐ray diffraction. An irreversible structural conversion from crystalline silicon to amorphous silicon takes place during the initial cycles, leading to ultrafast reversible sodium insertion in the newly generated amorphous silicon. Furthermore, an optimized silicon/carbon composite has been developed to further improve its electrochemical performance.

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Background The COVID-19 pandemic seriously endangers the public's mental health, especially to pregnant and postpartum women. But little is known about postpartum depression and health care needs among Chinese postpartum women. Aim To investigate the status and risk factors of postpartum depression and health care needs among Chinese postpartum women during the COVID-19 pandemic. Methods In this cross-sectional study, 209 Chinese postpartum women were recruited from May to July 2020 by convenience sampling and assessed online with self-designed Maternal General Information Questionnaire, Edinburgh Postpartum Depression Scale (EPDS) and Chinese Version of the Perceived Stress Scale (CPSS). Descriptive statistics, chi-square test, independent samples t -test, one-way ANOVA, Pearson correlation and multiple linear regression were used for data analysis. Results With the EPDS cut-off value of 10, the incidence of postpartum depressive symptoms was 56.9%. Age, history of abortion and perceived stress were the influencing factors of postpartum depression (adjusted R 2 = 0.432, F = 23.611, p < .001). The top three health care needs were infant rearing guidance (78.0%), maternal and infant protection guidance (60.3%) and dietary guidance (45.0%). The proportion of psychological rehabilitation guidance needs in the depressed group was significantly higher than that in the non-depressed group (34.5% vs. 20.0%, p < .05). Conclusions Maternal postpartum depression in China was at a high level during the COVID-19 pandemic. Women aged 25–34, with a history of abortion and high stress levels were at higher risk for postpartum depression. Timely psychological counselling, intervention and COVID-19-related health education are in great need for postpartum women.

Exploring economically efficient electrocatalysts with good electrocatalytic activity is essential for diverse electrochemical energy devices. Series of ultrathin metallic nickel-based holey nitride nanosheets were designed as bifunctional catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). They exhibit improved catalytic properties owing to the inherent advantages of their plentiful active reaction sites resulting from the complete exposure of the atoms in the large lateral surfaces and from the edges of pore areas, together with expanded lattice spacing distance. This obtained three-dimensional conductive integral architecture can not only accelerate the electron transportation by the highly orientated crystalline structure but also facilitate the diffusion of intermediate and gases. In terms of the OER electrocatalytic properties, a quite low overpotential (300 mV) is required for the holey two-dimensional (2D) Ni3Fe nitride nanosheets to deliver a current density of about 100 A g-1, with an enhanced improvement over IrO2by a factor of nearly 25 times. The holey 2D Ni3Fe nitride nanosheets also exhibit enhanced catalytic performance toward the HER, with a tiny overpotential (233 mV) to achieve a current density of about 100 A g-1with much better kinetic properties in comparison to those of highly active Pt/C.