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Abstract\nHIGHLIGHTSUnder the promotion of urban planning and land development policies, the urban spatial structure of China is undergoing a transformation towards polycentricity. The improvement of environmental performance during the process of urban spatial transformation is crucial for urban sustainable development. This paper uses high-resolution population grid data from LandScan for the years 2001–2019 to measure the urban spatial structure of Chinese cities. Then we match the Chinese Industrial Enterprise Database with the Chinese Industrial Enterprise Pollution Emission Database for the years 2001–2014. This paper empirically examines the impact and mechanisms of the polycentric spatial structure of Chinese cities on enterprise pollution reduction at the micro-level. The findings indicate that compared to monocentricity, polycentricity is more conducive to improving enterprise environmental performance. Mechanism tests demonstrate that the improvement in enterprise environmental performance resulting from polycentricity can be achieved through three channels: increasing urban population and density, mitigating urban environmental pollution, and promoting enterprise innovation ability. Heterogeneity analysis reveals that polycentricity is more beneficial for emission reduction among small enterprises, young enterprises and enterprises in regions with higher environmental regulations. This paper provides micro-level evidence and policy implications for further strengthening the aggregation effect of polycentricity and improving enterprise environmental performance in the future.We quantify urban spatial structure using Landscan data in China.Polycentricity is conductive to the enterprise emission reduction of so2.Polycentricity reduces enterprise emission by improving population scale and density.Reliving urban pollution, improving enterprise innovation are also mechanisms.Polycentricity is common in the southeast, southwest and northeast cities of China. [ABSTRACT FROM AUTHOR]

Transition metal nitride negative electrode materials with a high capacity and electronic conduction are still troubled by the large volume change in the discharging procedure and the low lithium ion diffusion rate. Synthesizing the composite material of F-doped Fe3N and an N-doped porous carbon framework will overcome the foregoing troubles and effectuate a preeminent electrochemical performance. In this study, we created a simple route to obtain the composite of F-doped Fe3N nanoellipsoids and a 3D N-doped porous carbon framework under non-ammonia atmosphere conditions. Integrating the F-doped Fe3N nanoellipsoids with an N-doped porous carbon framework can immensely repress the problem of volume expansion but also substantially elevate the lithium ion diffusion rate. When utilized as a negative electrode for lithium-ion batteries, this composite bespeaks a stellar operational life and rate capability, releasing a tempting capacity of 574 mAh g–1 after 550 cycles at 1.0 A g–1. The results of this study will profoundly promote the evolution and application of transition metal nitrides in batteries. [ABSTRACT FROM AUTHOR]

The advent of graphene opens up the research into two-dimensional (2D) materials, which are considered revolutionary materials. Due to its unique geometric structure, graphene exhibits a series of exotic physical and chemical properties. In addition, single-element-based 2D materials (Xenes) have garnered tremendous interest. At present, 16 kinds of Xenes (silicene, borophene, germanene, phosphorene, tellurene, etc.) have been explored, mainly distributed in the third, fourth, fifth, and sixth main groups. The current methods to prepare monolayers or few-layer 2D materials include epitaxy growth, mechanical exfoliation, and liquid phase exfoliation. Although two Xenes (aluminene and indiene) have not been synthesized due to the limitations of synthetic methods and the stability of Xenes, other Xenes have been successfully created via elaborate artificial design and synthesis. Focusing on elemental 2D materials, this review mainly summarizes the recently reported work about tuning the electronic, optical, mechanical, and chemical properties of Xenes via surface modifications, achieved using controllable approaches (doping, adsorption, strain, intercalation, phase transition, etc.) to broaden their applications in various fields, including spintronics, electronics, optoelectronics, superconducting, photovoltaics, sensors, catalysis, and biomedicines. These advances in the surface modification of Xenes have laid a theoretical and experimental foundation for the development of 2D materials and their practical applications in diverse fields. [ABSTRACT FROM AUTHOR]

Borophene, a promising material with potential applications in electronics, energy storage, and sensors, is successfully grown as a monolayer on Ag(111), Cu(111), and Au(111) surfaces using molecular beam epitaxy. The growth of two-dimensional borophene on Ag(111) and Au(111) is proposed to occur via surface adsorption and boron segregation, respectively. However, the growth mode of borophene on Cu(111) remains unclear. To elucidate this, scanning tunneling microscopy in conjunction with theoretical calculations is used to study the phase transformation of boron nanostructures under post-annealing treatments. Results show that by elevating the substrate temperature, boron nanostructures undergo an evolution from amorphous boron to striped-phase borophene (η = 1/6) adhering to the Cu ⟨ 1 1 ¯ 0 ⟩ $\langle {1\bar{1}0} \rangle $ step edge, and finally to irregularly shaped β-type borophene (η = 5/36) either on the substrate surface or embedded in the topmost Cu layer. dI/dV spectra recorded near the borophene/Cu lateral interfaces indicate that the striped-phase borophene is a metastable phase, requiring more buckling and electron transfer to stabilize the crystal structure. These findings offer not only an in-depth comprehension of the β-type borophene formation on Cu(111), but also hold potential for enabling borophene synthesis on weakly-binding semiconducting or insulating substrates with 1D active defects., (© 2023 Wiley-VCH GmbH.)