P2‐type layered oxides suffer from an ordered Na+/vacancy arrangement and P2→O2/OP4 phase transitions, leading them to exhibit multiple voltage plateaus upon Na+ extraction/insertion. The deficient ...sodium in the P2‐type cathode easily induces the bad structural stability at deep desodiation states and limited reversible capacity during Na+ de/insertion. These drawbacks cause poor rate capability and fast capacity decay in most P2‐type layered oxides. To address these challenges, a novel high sodium content (0.85) and plateau‐free P2‐type cathode‐Na0.85Li0.12Ni0.22Mn0.66O2 (P2‐NLNMO) was developed. The complete solid‐solution reaction over a wide voltage range ensures both fast Na+ mobility (10−11 to 10−10 cm2 s−1) and small volume variation (1.7 %). The high sodium content P2‐NLNMO exhibits a higher reversible capacity of 123.4 mA h g−1, superior rate capability of 79.3 mA h g−1 at 20 C, and 85.4 % capacity retention after 500 cycles at 5 C. The sufficient Na and complete solid‐solution reaction are critical to realizing high‐performance P2‐type cathodes for sodium‐ion batteries.
A high sodium content (0.85) and plateau‐free P2‐type cathode, Na0.85Li0.12Ni0.22Mn0.66O2, is developed for sodium‐ion batteries. The sodium content promises a large specific capacity of 123.4 mA h g−1 with an average working voltage as high as 3.5 V. The complete solid‐solution reaction over a wide voltage range ensures small volume variation (1.7 %) and fast Na+ kinetics (10−10 to 10−11 cm2 s−1), contributing to both excellent cycling stability and rate capability.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Nickel‐rich layered materials LiNi1‐x‐yMnxCoyO2 are promising candidates for high‐energy‐density lithium‐ion battery cathodes. Unfortunately, they suffer from capacity fading upon cycling, especially ...with high‐voltage charging. It is critical to have a mechanistic understanding of such fade. Herein, synchrotron‐based techniques (including scattering, spectroscopy, and microcopy) and finite element analysis are utilized to understand the LiNi0.6Mn0.2Co0.2O2 material from structural, chemical, morphological, and mechanical points of view. The lattice structural changes are shown to be relatively reversible during cycling, even when 4.9 V charging is applied. However, local disorder and strain are induced by high‐voltage charging. Nano‐resolution 3D transmission X‐ray microscopy data analyzed by machine learning methodology reveal that high‐voltage charging induced significant oxidation state inhomogeneities in the cycled particles. Regions at the surface have a rock salt–type structure with lower oxidation state and build up the impedance, while regions with higher oxidization state are scattered in the bulk and are likely deactivated during cycling. In addition, the development of micro‐cracks is highly dependent on the pristine state morphology and cycling conditions. Hollow particles seem to be more robust against stress‐induced cracks than the solid ones, suggesting that morphology engineering can be effective in mitigating the crack problem in these materials.
Significant oxidation state inhomogeneities induced by high‐voltage charging are revealed for Ni‐rich Li ion battery cathode material by the machine‐learning methodology data analysis of nano‐resolution 3D transmission X‐ray microscopy. The formation and propagation of micro‐cracks are proven to be dependent on the morphology of secondary particles and cycling conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Single‐atom catalysts (SACs) show great promise for electrochemical CO2 reduction reaction (CRR), but the low density of active sites and the poor electrical conduction and mass transport of the ...single‐atom electrode greatly limit their performance. Herein, we prepared a nickel single‐atom electrode consisting of isolated, high‐density and low‐valent nickel(I) sites anchored on a self‐standing N‐doped carbon nanotube array with nickel–copper alloy encapsulation on a carbon‐fiber paper. The combination of single‐atom nickel(I) sites and self‐standing array structure gives rise to an excellent electrocatalytic CO2 reduction performance. The introduction of copper tunes the d‐band electron configuration and enhances the adsorption of hydrogen, which impedes the hydrogen evolution reaction. The single‐nickel‐atom electrode exhibits a specific current density of −32.87 mA cm−2 and turnover frequency of 1962 h−1 at a mild overpotential of 620 mV for CO formation with 97 % Faradic efficiency.
If I had a nickel: An efficient NiI single‐atom electrode for the electrochemical CO2 reduction reaction is realized by combining the advantages of a single‐atom catalyst and a self‐standing nanoarray architecture.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Three-dimensional biofilm-electrode reactors (3D-BERs), which possess a large effective area to drive the reductive degradation of contaminants, have recently attracted attention for wastewater ...treatment. There have been few studies of the potential and risks of the application of this system on the removal of antibiotics. Here four 3D-BERs were designed to initially assess the potential for electrical stimulation to remove sulfamethoxazole (SMX), tetracycline (TC) and chemical oxygen demand, and to study the fate of the corresponding antibiotic resistance genes. The results indicated that the 3D-BER could significantly reduce antibiotic concentrations in wastewater, achieving removal rates of 88.9–93.5% and 89.3–95.6% for SMX and TC, respectively. The concentrations of target genes (sulI, sulII, sulIII, tetA, tetC, tetO, tetQ, and tetW) in a granular-activated carbon (GAC) cathode were higher than those in a GAC anode in the 3D-BR (reactor with biological sludge and no voltage) and 3D-BER. An obvious increasing trend in the relative abundances of all target genes was observed in the GAC. A low current density could not increase the development of sul and tet genes in the 3D-BER. The total resistance was in the following order: 3D-BER > 3D-BR > 3D-ER (reactor with 0.8 V and without biological sludge). In addition, the dehydrogenase activity of the microorganisms in the 3D-BER was significantly higher than in the 3D-BR (p < 0.05). High-throughput sequencing revealed that the microbial communities and relative abundance at the phyla level were affected by current stimulation.
•Satisfactory removal of sulfamethoxazole and tetracycline were acquired in 3D-BER.•Antibiotic resistance genes in a GAC cathode were higher than those in a GAC anode.•A low current density could not increase the development of antibiotic resistance genes.•Microbial communities were significantly affected by current stimulation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Emerging divided cities in China Shen, Jie; Xiao, Yang
Urban studies (Edinburgh, Scotland),
05/2020, Volume:
57, Issue:
6
Journal Article
Peer reviewed
Compared with North America andWestern Europe, Chinese cities used to feature a low extent of socioeconomic segregation. However, systematic analysis of the changes in socioeconomic segregation after ...the end of the provision of welfare housing is needed. Using residential-committeelevel data from the fifth and sixth censuses of Shanghai, for the first time, this article systematically charts changes in socioeconomic segregation in Chinese cities over the period 2000–2010. Along with the emergence of high-status neighbourhoods and migrant neighbourhoods, Shanghai has grown more divided based on individual socioeconomic status. The extent of socioeconomic segregation in Shanghai was comparable to that of large US and European cities. While patterns of sociospatial divisions are different across central and suburban areas, the level of educational segregation becomes greater than that of hukou segregation. The crucial role of housing commodification in driving these changes highlights the importance of contextual and institutional factors in understanding the dynamics of segregation.
与北美和西欧相比，中国城市过去的社会经济隔离程度较低。但是，我们需要对福利住房供应结束后社会经济隔离的变化进行系统分析。本文首次利用上海第五次和第六次人口普查的居委会层面数据，系统地描述了2000 - 2010年中国城市社会经济隔离的变化情况。随着高档社区和移民社区的出现，上海在个人社会经济地位方面变得更加分化。上海的社会经济隔离程度与美国和欧洲大城市相当。虽然市中心和郊区的社会空间割裂情况不同，但教育隔离的程度已经大于户口隔离的程度。住房商品化在推动这些变化方面的关键作用凸显了背景直觉因素在理解隔离动态方面的重要性。
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To effectively stabilize coarse sand, bentonite was introduced in microbially induced carbonate precipitation (MICP) grouting. Varying concentrations (0, 20, 40, and 80 g/L) of bentonite were added ...to bacterial suspensions (BSs), which were magnetically stirred to form bacterial-bentonite suspensions (BBSs). Then, coarse sand specimens were treated with BBSs and cementation solutions (CSs) to different cementation levels. The results showed that the addition of bentonite could increase the volume fractions of the precipitates consisting of calcium carbonate (CaCO
3
) and bentonite. The permeability decreased exponentially as the volume fraction of precipitates increased. As the active precipitates increased when a lower concentration (e.g., 20 g/L) of bentonite was added to the MICP grouting, the unconfined compressive strength (UCS) was substantially improved. However, detrimental effects were observed for specimens treated with a high concentration of bentonite. These results indicate that the effective concentration of natural clay aggregates used in MICP grouting was different for different engineering applications, e.g., seepage control and strength enhancement. The current work provides an encouraging method of improving the MICP technique.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Simply yet powerfully, single-atom catalysts (SACs) with atomically dispersed metal active centers on supports have received a growing interest in a wide range of catalytic reactions. As a specific ...example, SACs have exhibited distinctive performances in CO
chemical conversions. The unique structures of SACs are appealing for adsorptive activation of CO
molecules, transfer of intermediates from support to active metal sites, and production of desirable products in CO
conversion. In this Account, we have exemplified our recent endeavors in the development of SACs toward CO
conversions in thermal catalysis and electrocatalysis. In terms of the support not only stabilizing but also working collaboratively with the single active sites, the proper choice of support is of great importance for its stability, activity, and selectivity in single-atom catalysis. Three distinctive strategies for SAC architectures-lattice-matched oxide supported, heteroatom-doped carbon anchored, and mimetic ligand chelated-are intensively discussed from the perspective of support design for SACs in different reaction environments. To achieve a high-temperature thermal reduction of CO
to CO, TiO
(rutile), lattice-matched to the IrO
active site, was chosen as a support to realize the thermal stability of Ir
/TiO
SAC, and it shows great capability toward CO
conversion and excellent selectivity to CO due to the effective block of the over-reduction of CO
to methane over single Ir active sites. In the electrochemical reduction of CO
at low temperature, sulfur co-doped N-graphene was developed to achieve unique d
-Ni single atoms on the conductive graphene support, by which not only were the atomic Ni active sites trapped into the matrix of graphene for its stabilization, but also the modulation of electronic configuration of mononuclear Ni centers promoted the CO
activation through facile electron transfer with an improved electroreduction activity. Inspired by the Ir mononuclear homogeneous catalysts in CO
hydrogenation to formate, porous organic polymers (POPs) functionalized with a reticular aminopyridine group were purposely fabricated to mimic the homogeneous ligand environment for chelating the Ir single-atom active center, and this quasi-homogeneous Ir
/POP catalyst manifests high efficiency for hydrogenation of CO
to formate under mild conditions in the liquid phase. Such SACs are of paramount importance for the transformation of CO
, with their coordination environment helping in the activation of CO
. Since the energy barrier for the dissociation of the second C-O bond of CO
on single-atom sites is very high, these catalysts can give high selectivities toward CO or formate products. Thanks to SACs, the conversion of CO
has become much easier in various chemical environments.
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IJS, KILJ, NUK, PNG, UL, UM
The evolution of cost‐effective and reserve‐rich nonprecious metals (NPMs) to replace precious metal electrocatalysts is of significant interest in modern electrocatalysis. The confinement effects in ...NPM‐based nanoparticles encapsulated in carbon nanoshells have been considered as an emerging and efficient way to special types of electrocatalysts which facilitate electrocatalytic activity and stability, even under rigorous conditions. This review focuses on the unique individual carbon encapsulation for high‐performance design of NPM‐based electrocatalysts, outlining all confinement synthesis methods, mechanistic studies on confinement effects, and the emerging practical reactions. It begins first introducing the synthetic methods for NPM‐based core@carbon shell electrocatalysts, and then follows clarification of the relationship between the fundamental confinement effects and the performance improvement of carbon shell encapsulating NPM‐based electrocatalysts. Further and detailed discussions on the alloying effect, doping effect, and heterojunction effect of the NPM‐based core to alter the electronic situation which affects the electrocatalytic performance are subsequently provided. Finally, the review provides a perspective on challenges and opportunities in future research with respect to both in‐depth theoretical research and potential design concept of such NPM‐based core@carbon shell electrocatalysts.
Individual nonprecious metal (NPM)‐based core@carbon shell electrocatalysts have attracted extensive attention as one of the promising electrocatalytic materials. Confined within the carbon shell endows the integral electrocatalysts with good physical and chemical properties. Further alloying, doping, and heterojunction design of the cores provide abundant options for diverse electrocatalytic reactions. The structure–performance relationship is comprehensively reviewed via the experimental results and theoretical calculations.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Fast charging is a key enabler of mainstream adoption of electric vehicles (EVs). None of today’s EVs can withstand fast charging in cold or even cool temperatures due to the risk of lithium plating. ...Efforts to enable fast charging are hampered by the trade-off nature of a lithium-ion battery: Improving low-temperature fast charging capability usually comes with sacrificing cell durability. Here, we present a controllable cell structure to break this trade-off and enable lithium plating-free (LPF) fast charging. Further, the LPF cell gives rise to a unified charging practice independent of ambient temperature, offering a platform for the development of battery materials without temperature restrictions. We demonstrate a 9.5 Ah 170 Wh/kg LPF cell that can be charged to 80% state of charge in 15 min even at −50 °C (beyond cell operation limit). Further, the LPF cell sustains 4,500 cycles of 3.5-C charging in 0 °C with <20% capacity loss, which is a 90× boost of life compared with a baseline conventional cell, and equivalent to >12 y and >280,000 miles of EV lifetime under this extreme usage condition, i.e., 3.5-C or 15-min fast charging at freezing temperatures.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Detecting objects and estimating their viewpoints in images are key tasks of 3D scene understanding. Recent approaches have achieved excellent results on very large benchmarks for object detection ...and viewpoint estimation. However, performances are still lagging behind for novel object categories with few samples. In this paper, we tackle the problems of few-shot object detection and few-shot viewpoint estimation. We demonstrate on both tasks the benefits of guiding the network prediction with class-representative features extracted from data in different modalities: image patches for object detection, and aligned 3D models for viewpoint estimation. Despite its simplicity, our method outperforms state-of-the-art methods by a large margin on a range of datasets, including PASCAL and COCO for few-shot object detection, and Pascal3D+ and ObjectNet3D for few-shot viewpoint estimation. Furthermore, when the 3D model is not available, we introduce a simple category-agnostic viewpoint estimation method by exploiting geometrical similarities and consistent pose labeling across different classes. While it moderately reduces performance, this approach still obtains better results than previous methods in this setting. Last, for the first time, we tackle the combination of both few-shot tasks, on three challenging benchmarks for viewpoint estimation in the wild, ObjectNet3D, Pascal3D+ and Pix3D, showing very promising results.
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