Electrochemical Decalcification-Exfoliation of Two-Dimensional Siligene, SixGey: Material Characterization and Perspectives for Lithium-Ion Storage

A two-dimensional (2D) silicene-germanene alloy, siligene (SixGey), a single-phase material, has attracted increased attention due to its two-elemental low-buckled composition and unique physics and chemistry. This 2D material has the potential to address the challenges caused by low electrical conductivity and the environmental instability of corresponding monolayers. Yet, the siligene structure was studied in theory, demonstrating the material’s great electrochemical potential for energy storage applications. The synthesis of free-standing siligene remains challenging and therefore hinders the research and its application. Herein we demonstrate nonaqueous electrochemical exfoliation of a few-layer siligene from a Ca1.0Si1.0Ge1.0 Zintl phase precursor. The procedure was conducted in an oxygen-free environment applying a −3.8 V potential. The obtained siligene exhibits a high quality, high uniformity, and excellent crystallinity; the individual flake is within the micrometer lateral size. The 2D SixGey was further explored as an anode material for lithium-ion storage. Two types of anode have been fabricated and integrated into lithium-ion battery cells, namely, (1) siligene-graphene oxide sponges and (2) siligene-multiwalled carbon nanotubes. The as-fabricated batteries both with/without siligene exhibit similar behavior; however there is an increase in the electrochemical characteristics of SiGe-integrated batteries by 10%. The corresponding batteries exhibit a 1145.0 mAh·g-1 specific capacity at 0.1 A·g-1. The SiGe-integrated batteries demonstrate a very low polarization, confirmed by their good stability after 50 working cycles and a decrease in the solid electrolyte interphase level that occurs after the first discharge/charge cycle. We anticipate the growing potential of emerging two-component 2D materials and their great promise for energy storage and beyond.10 página

Multiscale Analysis of the Gold Dust Defect in AISI 430 Industrial Stainless Steels: Influence of the Aluminum Content

The "Gold Dust Defect" affects the surface quality of AISI 430 ferritic stainless steels. However, there is a very limited number of studies focusing on it. To better understand its nature, we have combined several techniques, such as x-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron microscopy, in order to extract a maximum of structural and compositional information. Our results show that the surface quality, microstructure, and chemistry of the samples are strongly affected by the aluminum content, the severity of the defect being the highest at the lowest Al concentration. Not only is the concentration of the defects at the surface strongly reduced when increasing the Al. at.% but the depth of the cavities is also reduced by a factor of 3 when the Al content is increased from 0.09 at.% to 0.59 at.%. Our results provide new information on the nature of this defect, and show that an increase of the aluminum content allows the Cr concentration to be maintained in the range of values required to maintain the passivity of the steel, thus improving the surface quality

Improved electrochemical conversion of CO2 to multicarbon products by using molecular doping

The conversion of CO2 into desirable multicarbon products via the electrochemical reduction reaction holds promise to achieve a circular carbon economy. Here, we report a strategy in which we modify the surface of bimetallic silver-copper catalyst with aromatic heterocycles such as thiadiazole and triazole derivatives to increase the conversion of CO2 into hydrocarbon molecules. By combining operando Raman and X-ray absorption spectroscopy with electrocatalytic measurements and analysis of the reaction products, we identified that the electron withdrawing nature of functional groups orients the reaction pathway towards the production of C2+ species (ethanol and ethylene) and enhances the reaction rate on the surface of the catalyst by adjusting the electronic state of surface copper atoms. As a result, we achieve a high Faradaic efficiency for the C2+ formation of approximate to 80% and full-cell energy efficiency of 20.3% with a specific current density of 261.4 mA cm(-2) for C2+ products. Strategies to systematically tune CO2 electroreduction to multicarbon products are of high interests. Here the authors report electron withdrawing functional group alters the reaction pathway towards C2+ products by adjusting the oxidation state of surface copper.D.V., K.Q., and H.L.W. acknowledge funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 804320). L.L., D.V., and H.L.W acknowledge the use of TEM instrumentation provided by the Nation Facility ELECMI ICTS (`Division de Microscopia Electronica', Universidad de Cadiz, DME-UCA). L.L. acknowledges funding from the Andalusian regional government (FEDER-UCA-18-106613), the European Union's Horizon 2020 research and innovation program (grant agreement 823717-ESTEEM3), and the Spanish Ministerio de Economia y Competitividad (PID2019-107578GA-I00). K.Q. and Y.Z. acknowledge financial support from the China Postdoctoral Science Foundation (2018M633127) and the Natural Science Foundation of Guangdong Province (2018A030310602). J.L. acknowledge financial support from the National Natural Science Foundation of China (21808134). We thank Soleil Synchrotron and Andrea Zitolo for allocating beamtime at beamline Samba within the proposal 20200732

A high-performance “fueled” photodetector based on few-layered 2D ternary chalcogenide NiGa2S4

Few-layered binary 2D transition metal chalcogenides have been comprehensively employed in photodetector systems thanks to their intrinsic band gap structure and a high in-plane charge carrier mobility. Their rich chemistry is further broadened when considering ternary 2D chalcogenide materials, giving the possibility to prepare isomorphic materials characterized by various metal distributions within the framework of a crystal structure. Whereas the “inverse” A(τ)B(Ω)(τ)2X4 hexagonal structures (e.g. ZnIn2S4) have been widely studied in photocatalysis, “normal” AII(Ω) BIII(τ)2XVI4 phases have not been considered so far. In this study, a NiGa2S4 photodetector has been prepared by drop-casting the exfoliated crystals onto ITO glass. Their photoresponse has been analyzed either in the absence or in the presence of an electron donor species (EtOH) in the electrolyte solution. Ethanol acts as a fuel in the PEC photodetector system boosting their performance by a factor of ∼x49 in terms of the responsivity at a given wavelength. Moreover, the spectral response is expanded from blue to far IR wavelengths, reaching responsivity values from 48 to 7 mA W−1. The dynamics of photogenerated electrons and holes has been studied using laser flash photolysis. The stability of the “fueled” PEC photodetector has been evaluated through long-term tests which have shown a stable response over extended periods. It is anticipated that the present work can provide fundamental insight into the field of PEC semiconductor-based photodetectors, offering an extendable strategy to engineer high-performance PEC devices.11 página

Erratum: Photocatalytic removal of benzene over Ti3C2Tx MXene and TiO2-MXene composite materials under solar and NIR irradiation (J. Mater. Chem. C (2022) 10 (626–639) DOI: 10.1039/D1TC03826E)

Corrección del artículo: Photocatalytic removal of benzene over Ti3C2T: XMXene and TiO2-MXene composite materials under solar and NIR irradiation. Journal of Materials Chemistry C, Volume 10, Issue 2, Pages 626 - 639, 14 January 2022The authors regret the omission of the following two sentences from the Acknowledgements section of the published article: Gabriel Constantinescu acknowledges the support of the TEOsINTE project (Grant agreement ID: 101003375), funded under the H2020-EU.4.Programmes (Funding Scheme: MSCA-IF-EF-ST – Standard EF). This project has received funding from the European Union’s Horizon 2020 research and innovation programme. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and reader.1 página