The coordinated configuration of atomic platinum (Pt) has always been identified as an active site with high intrinsic activity for hydrogen evolution reaction (HER). Herein, we purposely synthesize single vacancies in a carbon matrix (defective graphene) that can trap atomic Pt to form the Pt–C3 configuration, which gives exceptionally high reactivity for HER in both acidic and alkaline solutions. The intrinsic activity of Pt–C3 site is valued with a turnover frequency (TOF) of 26.41 s–1 and mass activity of 26.05 A g–1 at 100 mV, respectively, which are both nearly 18 times higher than those of commercial 20 wt % Pt/C. It is revealed that the optimal coordination Pt–C3 has a stronger electron-capture ability and lower Gibbs free energy difference (ΔG), resulting in promoting the reduction of adsorbed H+ and the acceleration of H2 desorption, thus exhibiting the extraordinary HER activity. This work provides a new insight on the unique coordinated configuration of dispersive atomic Pt in defective C matrix for superior HER performance.

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The hydrazine oxidation reaction (HzOR) is structuresensitive, and a slight modification of the catalyst structure can generate a significant change in activity. To date, no study on the size effect of the catalyst at a subnanometer scale on HzOR has been reported yet. Herein, we report the fabrication of Pd species with sizes ranging from nanoparticles (NPs) and nanoclusters (NCs) to single atoms (SAs) onto a NiFe-layered double hydroxide by fine-tuning precursors and reduction methods. When applied for the electro-oxidation dehydrogenation of hydrazine, the as-prepared Pd NCs/ NiFe exhibit a current density of 4.3 A mg Pd −1 at 0.35 V versus RHE. It should be noted that the mass activity of Pd NCs/NiFe was 36 times that of Pd SAs/ NiFe and 7 times that of Pd NPs/NiFe, respectively. The in situ electrochemical impedance spectroscopy and density functional theory calculation demonstrate that different from previous studies, both the Pd SAs/NiFe and Pd NPs/NiFe are suboptimal in HzOR due to the isolated active sites of the Pd SAs/NiFe and large steric hindrance of Pd NPs/NiFe, respectively. Instead, the strong intracluster interactions of Pd NCs/NiFe lift the d-band center closer to the Fermi level, leading to stronger hybridization of Pd d-orbitals and the σ orbitals of N 2 H 4 molecules. Consequently, the excellent performance of Pd NCs/NiFe can be attributed to its multiple neighboring metal sites, high d-band center, and small steric hindrance.

Background Hierarchical medical systems are common in developed countries, but it’s not optimistic in China. This study aimed to identify the factors affecting healthcare-seeking behavior among pregnant women in Guangdong, China. Methods We conducted a cross-sectional, observational survey, developed using the Andersen’s behavioral model. Pregnant women were randomly selected using a two-stage, stratified, random sampling method from hospitals in Guangdong, China. A multinomial logistic regression was used to identify statistically significant variables from aspect of environmental, demographic and pregnancy characteristics associated with pregnant women seeking healthcare at primary, secondary or tertiary hospitals. Results A total of 1393 pregnant women returned the survey after attending 1 of 12 hospitals within 4 cities of the Guangdong province: 537 (38.5%) of the respondents attended a primary hospital, 437 (31.4%) a secondary hospital, and 419 (30.1%) a tertiary hospital. Women attending primary hospitals were more likely to live closer to the hospital, live rurally, and be educated to a lower level. Several factors were significantly associated with attendance at a secondary vs a primary hospital: the woman’s perceived necessity to seek maternal healthcare (OR 1.73, 95% CI [1.1,2.74]), the woman’s choice of delivery hospital (OR 1.45, 95% CI [1.01,2.07]), or urban living (OR 1.39, 95% CI [1.03,1.88]). Characteristics associated with attendance at a tertiary vs a primary hospital were: a history of pregnancy complications (OR 2.35, 95% CI [1.43,3.86]), travel to the hospital by public transport/taxi (OR 2.09/2.67, 95% CI [1.35,3.22]/ [1.45,4.92]), urban living (OR 1.58, 95% CI [1.14,2.18]), or a planned current pregnancy (OR 1.53, 95% CI [1.07,2.19]). Conclusion Medical needs and convenience both play a role in the choice of hospital for antenatal care, and impact on equity utilization of health services. Pregnant women without risk factors and with higher levels of education should be a target population for guiding to choose a more proper level of hospital.