[en] To reduce the severe overpotential of oxygen reduction and evolution reaction (ORR and OER) for rechargeable Li-O₂ batteries, the dandelion-like α-MnO₂ hollow spheres (HS) with high surface area (105.54 m² g⁻¹) were prepared by a facile in situ pyrolysis of manganese alkoxide for the first time. The ORR diffusion limiting current density and OER current density at 1.0 versus (Ag/AgCl)/V are 6.32 and 45.82 mA cm⁻² at 1600 rpm in alkaline solution, respectively, indicating that dandelion-like α-MnO₂-HS catalyst exhibits superior bifunctional catalytic activity. The Li-O₂ batteries with α-MnO₂-HS catalyst can yield high initial discharge specific capacity of 7897.6 mA h g⁻¹ at 100 mA g⁻¹. Moreover, the cycle life of Li-O₂ batteries with α-MnO₂-HS catalyst is significantly improved and can sustain 108 cycles. These results indicate that as-fabricated hollow sphere structure without adding any hard templates is favorable for superior bifunctional catalytic activity in aqueous and non-aqueous electrolyte.

[en] The objective of this study was to investigate the adhesion, proliferation and mineralization of osteoblasts on arginine-glycine-aspartic acid (RGD)- and magnesium ion (Mg⁺)-decorated zirconia coatings. The zirconia coatings were prepared via a plasma spray; RGD and Mg⁺ were immobilized via a silane-coupling agent and ion implantation, respectively. This study employed scanning electron microscopy (SEM) to observe the surface morphology of RGD- and Mg⁺-decorated zirconia coatings; surface roughness and wettability were also measured. The initial adhesion of osteoblasts was measured, and cell morphology and focal adhesion were observed. In addition, the expressions of the integrins a1, a2, a5, av, and ß1 were measured using RT-PCR. A cell count was conducted to measure proliferation. The expressions of ALP and OCN were detected based on a western blot analysis, and mineralized nodules were observed to visualize the mineralization of osteoblasts. A nanoscale surface structure could be found on the Mg⁺-decorated zirconia coating, and the RGD-decorated zirconia coating showed better wettability (p < 0.05). Cells on the RGD- and Mg⁺-decorated zirconia coating possessed better spreading properties than did cells on nondecorated surfaces, and more focal adhesion was observed. The higher expressions of the integrins a5, av and ß1 were found on the RGD-decorated zirconia coating (p < 0.05). The western blot results demonstrated that the introduction of Mg⁺ heightened the expressions of ALP and OCN. More and bigger mineralized nodules were observed on the Mg⁺- and RGD-decorated zirconia coating, which consisted of small mineralized nodules. RGD- and Mg⁺-functionalized zirconia coating facilitates the osteogenic reaction of osteoblasts. RGD improves the adhesion of osteoblasts, and Mg⁺ benefits the mineralization of osteoblasts. In addition, a synergistic effect was found between RGD and Mg⁺, allowing better performances with regard to adhesion, proliferation and mineralization when the two were used together rather than as separate decorations.

[en] Highlights:• The mesoporous carbons with Fe-Nx and C–S–C active sites (Fe/S–N/Cs) were successfully synthesized via a facile strategy.• The Fe/S–N/C catalysts exhibit large specific surface areas (980.9 m² g⁻¹) and high pore volumes (0.556 cm³ g⁻¹).• MFC devices with the Fe/S–N/Cs catalysts exhibit higher maximum power density (1436.42 mW m⁻²) than that of commercial Pt/C. -- Abstract: An efficient catalyst (Fe/S–N/C) possessing abundant ordered mesoporous was synthesized via a facile strategy, in which the active Fe-N_x and C–S–C species exhibited atomic dispersion. Attributing to its well-developed porosity, the total pore volume and specific surface area of Fe/S–N/C catalyst reach 0.556 cm³ g⁻¹ and 980.9 m² g⁻¹ respectively. Electron microscopy results reveal the uniform dispersion of atomic Fe-N_x and C–S–C in this catalyst, which has inherited a polyhedral morphology derived from ZIF-8. X-ray spectroscopy measurements further validate that the Fe/S–N/C composite can provide abundant and highly efficient active sites for ORR. The atomic ratio of nitrogen is 4.28%, with high relative concentrations of the active pyridinic N and Fe-N_x. Furthermore, the Fe/S–N/C catalysts demonstrate significant ORR activity in the practical application of MFC devices. Based on a high open circuit potential (0.674 V) and maximum power density (1436.42 mW m⁻²) of the MFC device which uses the Fe/S–N/C as air-cathode catalyst, the Fe/S–N/C displays better catalytic activity than commercial 20% Pt/C catalyst. This investigation provides a new strategy to design an effective, low-cost ORR catalyst for MFC devices.

[en] Arid inland river basin has been regarded as environmental vulnerable and an important protective area in northwest China. Shiyang River Basin (SRB) is one of the most typical areas in arid inland rivers basin in China. The environmental quality evaluation of different periods is significant for environmental control and management of SRB. In this paper, the normalized differential vegetation index (NDVI), wetness index (WI), albedo, index-based built-up index (IBI), salinization index (SI), and land surface temperature (LST) were obtained through Landsat TM and OLI images in 1995, 2000, 2005, 2010, and 2016. Besides, three methods including spatial principal component analysis (SPCA), analytic hierarchy process (AHP), and remote-sensing spatial distance model (RSSDM) were compared to select a reasonable method for environmental evaluation. The AHP method was determined as the final method for objectively evaluating spatiotemporal changes of environment from 1995 to 2016 in SRB. The results showed that the environment deteriorated in 1995–2000 and improved in 2000–2016. The effect of environmental governance was significant in 2010–2016 because of the longtime environmental management between multiple departments. The results indicated that the environmental quality of SRB was generally improved from 1995 to 2016. We found that the improvement areas were mainly concentrated in the oasis and marginal areas, while environmental damage areas were mainly distributed in the urban regions. However, in most areas of the SRB, the environment was still below average level of China, and the roads of the environment management still had a long way to go. We found that spatiotemporal pattern analysis of the environment was of great importance for the formulation of plans for development of this basin and environmental protection measures.

[en] Highlights: • The mesoporous La_0.8Sr_0.2MnO₃ nanowires (LSMO-Mes-NW) were successfully prepared. • LSMO-Mes-NW exhibit high specific surface area of 31.03 m² g⁻¹. • The oxygen vacancy concentration and ratio of Mn⁴⁺/Mn³⁺ were precisely regulated. • LSMO-Mes-NW-based Zn-air batteries show high peak power density of 113.86 mW cm⁻². • DFT calculation reveals strengthened electrocatalytic mechanism by Sr dopants. The one-dimensional mesoporous La_0.8Sr_0.2MnO₃ catalysts with excellent electronic conduction were successfully prepared by molten salt template method to accelerate the kinetics of ORR for metal-air batteries. The as-synthesized mesoporous La_0.8Sr_0.2MnO₃ nanowires with relatively high oxygen vacancy concentration and ratio of Mn⁴⁺/Mn³⁺ show high specific surface area of 31.03 m² g⁻¹, higher than the most of reported perovskite oxides. More importantly, more catalytic active sites can be exposed at the three-phase interface of ORR due to high specific surface area. The mesoporous La_0.8Sr_0.2MnO₃ nanowires exhibit high half-wave potential and catalyze near 4 e⁻ ORR process. Besides, the one-dimensional mesoporous La_0.8Sr_0.2MnO₃-based Zn-air batteries show high peak power density of 113.86 mW cm⁻². Simultaneously, density functional theory (DFT) calculation reveals that strengthened electrocatalytic mechanism of La_1-xSr_xMnO₃ catalysts originates from lower formation energy of oxygen vacancy and more positive O 2p band center because of Sr dopants, which is consistent with the experimental results. Consequently, this investigation not only provide a new idea for developing mesoporous perovskite oxides nanowires but also reveals enhanced electrocatalytic mechanism of La_1-xSr_xMnO₃ catalysts.

[en] Highlights: • Methyl-mercaptan adsorbed carbon was hydrothermally treated. • Lactone group transformed into lactone radical. • Lactone radical reacted with adsorbed methyl mercaptan. • Graphene-oxide fragment was formed with a thickness of 0.9–1.0 nm. • Regenerated carbon regained adsorptive ability. Activated carbon was a widely-used adsorbent. However, it was usually classified as a hazardous waste after saturation adsorption for one pollution. For the first time, this article reported a regeneration method for the activated carbon saturated with methyl mercaptan. The regenerated carbon was partially transformed into graphene-oxide fragment with a thickness of 0.9–1.0 nm after a hydrothermal treatment at 180 °C. Electron paramagnetic resonance revealed that lactone group was transformed into lactone radical under the hydrothermal condition. The spins were increased from 4.54E+17–1.24E+18. The formed radical effectively reacted with the adsorbed methyl mercaptan and re-distributed the amorphous activated carbon to form lamellar graphene oxide. As a result, the spins were decreased from 1.24E+18–8.73E+17. At the same time, the amount of lactone group was decreased from 0.71 to 0.42 mmol/g. The regenerated activated carbon thus regained ability to adsorb methyl mercaptan. The main result of this paper puts forward a simple and low-cost method to obtain graphene oxide modified activated carbon from the regeneration of hazardous waste carbon. This conclusion makes contribution to the development of “zero-waste” conception.

[en] Herein, NiF₂ artificial interface was proposed for the first time to enhance the electrochemical performances of LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) under 4.5 V. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images verify NiF₂ layer is successfully constructed on the surface of NCM523. The 1.0 wt% NiF₂-modified NCM523 delivers a much higher capacity retention (86.9%) than pristine sample (69.0%) after 100 cycles under 4.5 V at 30 °C, even exceeding pristine NCM523 under 4.2 V (82.2%). Beyond that, the cycling stability of NCM523 under 4.5 V at 55 °C is also visibly improved due to the NiF₂ protective layer. Electrochemical impedance spectroscopy analyses confirm that NiF₂ suppresses the increase of interface resistance and therefore makes for the interface kinetics behaviors during cycling. In addition, the measurements of SEM, TEM and XPS support that the inhibition of the SEI (solid electrolyte interphase) growth can be attributed to the restrained side reactions between electrolyte and NCM523 by NiF₂ artificial layer at 4.5 V.

[en] Highlights: • Shiyang River basin was selected to study net primary production during 2001–2016. • We proposed a method to calculate effect of human activity on primary production. • Human activities strongly affected net primary production during 2001–2016. • Reducing human activities is beneficial to restore grassland productivity. Human activities have adversely impacted grassland net primary productivity (NPP) across the world, and quantitative estimations of the anthropogenic impacts on NPP (HNPP) can be helpful to improve environmental protection and climate adaptation measures. However, disentangling the effects of climate variability and human activities on NPP is problematic and requires the calculation of potential net primary productivity (PNPP). In this study, we assessed the anthropogenic impacts on NPP in the Shiyang River basin—a typical arid and semi-arid region. We used the seasonal changes in NPP to identify the grids that were not affected by human activity and then proposed a method to calculate PNPP based on the leaf area index (LAI). We estimated the actual net primary productivity (ANPP) using the Carnegie-Ames-Stanford Approach (CASA) model, and the HNPP was then calculated as the difference between ANPP and PNPP. Our results showed that this method for PNPP calculation was reliable. From 2001 to 2016, the positive (90.85 gC·m⁻²·a⁻¹) and negative effects (−130.21 gC·m⁻²·a⁻¹) of human activities on NPP accounted for 32.68% and 46.84% of the ANPP, respectively, and the overall average HNPP was −39.36 g C·m²·a⁻¹. The implementation of ecological and environmental protection projects gradually mitigated the negative effects of human activity on NPP at a rate of 4.55 gC·m⁻²·a⁻¹; however, negative HNPP values still occupied 55.39% of the entire region in 2016. In contrast with the prevailing views that climate change is the main factor accounting for vegetation recovery in arid and semi-arid regions, our results suggest that reducing human activities can significantly promote environmental restoration. The findings of this study suggest that policy makers and stakeholders can restore grassland ecosystems and promote environmental protection by reducing anthropogenic activities in arid and semi-arid regions.