Inhibition of the reduction of Cr(VI) at the magnetite–water interface by calcium carbonate coatings

The effect of calcium carbonate coatings on the reduction of aqueous chromate on the magnetite(1 1 1) surface has been investigated using a combination of synchrotron based X-ray photoemission spectroscopy (PES) and X-ray absorption near edge structure (XANES) spectroscopy, along with laboratory-based powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). CaCO₃ coatings (dominantly calcite with minor quantities of aragonite and vaterite) of thicknesses ranging from 10 Å to 20 m were grown on magnetite(1 1 1) surfaces by exposure to supersaturated aqueous solutions followed by evaporation of the solution—a process that mimics pore-water evaporation in vadose zones leading to the formation of caliche and calcium carbonate coatings on mineral grains. Coating thicknesses were determined from attenuation of the Fe 2p photoemission signal by the carbonate coating. For coatings less than 15 Å thick, Cr 2p photoemission and Cr L_II, L_III-edge XANES spectra show that chromate is reduced by the underlying magnetite surface; however, as the minimum coating thickness increases beyond 15 Å, the magnetite surface becomes passivated and further chromate reduction ceases. Our findings suggest that carbonate coatings on natural magnetite grains can significantly reduce or eliminate their ability to reduce Cr(VI), which is a toxic and highly mobile environmental contaminant.     

载波钝化和钼酸盐后处理对不锈钢钝化膜性能的影响

一般认为交流电对金属的腐蚀过程具有加速作用,但我们发现,在直流电位基础上叠加适当波形、幅值和频率的交流电对不锈钢进行载波钝化,尔后再进行适当后处理可使钝化膜的稳定性提高,我们曾就不经后处理的载波钝化过程进行过探讨,本文着重探讨钼酸盐后处理对载波钝化膜表面状态和化学稳定性改善的作用机理。     

Adsorptive passivation of iron by organic acid anions

Studies on the iron passivation by organic acid anions in aqueous solutions are briefly reviewed. It is shown that the passivation can be caused only by their adsorption, retarding both the iron dissolution and the formation of oxide films. Earlier, it had been believed that oxide films play a dominant role in the iron passivation in neutral solutions. The recent viewpoint is that such nonoxide iron passivation can occur in solutions of salts of not only aromatic amino acids (sodium phenylantranilate and its substitutes), but other carboxylic acids as well. An important role of chemisorption and hydrophobic properties of anions for the formation of adsorption passive films is emphasized. New possibilities for inhibitor protection of iron against corrosion, which is based on adsorptive passivation, are pointed out.Translated from Elektrokhimiya, Vol. 40, No. 12, 2004, pp. 1503–1507.Original Russian Text Copyright © 2004 by Kuznetsov.     

流动注射区域采样法测定镀锌钝化液中高浓度锌

本文建立了流动注射二甲酚橙光度法测定镀锌纯化液中Ｚｎ￣２＋的自动分析方法。利用区域采样技术和调整管路参数自动完成对样品的上千倍稀释，确定了最佳分析条件并研究了干扰离子的影响及消除办法。所建方法仪器简单，分析速度为８４次／小时，变异系数（Ｚｎ￣２＋１６．０ｇ／Ｌ，ｎ＝２０）为１．Ｏ％，用于实际钝化液分析，相对误差小于±１０％。     

Efficient polymer passivation of ligand‐stripped nanocrystal surfaces

Water‐dispersible, polymer‐wrapped nanocrystals are highly sought after for use in biology and chemistry, from nanomedicine to catalysis. The hydrophobicity of their native ligand shell, however, is a significant barrier to their aqueous transfer as single particles. Ligand exchange with hydrophilic small molecules or, alternatively, wrapping over native ligands with amphiphilic polymers is widely employed for aqueous transfer; however, purification can be quite cumbersome. We report here a general two‐step method whereby reactive stripping of native ligands is first carried out using trialkyloxonium salts to reveal a bare nanocrystal surface. This is followed by chemically directed immobilization of a hydrophilic polymer coating. Polyacrylic acids, with side‐chain grafts or functional end groups, were found to be extremely versatile in this regard. The resulting polymer‐wrapped nanocrystal dispersions retained much of the compact size of their bare nanocrystal precursors, highlighting the unique role of monomer side‐chain functionality to serve as effective, conformal ligation motifs. As such, they are well poised for applications where tailored chemical functionality at the nanocrystal's periphery or improved access to their surfaces is desirable. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Addition reaction and characterization of chlorotris(triphenylphosphine)iridium(I) on silicon(1 1 1) surfaces

Studies were performed to determine the chemical addition of a metal complex molecule, chlorotris(triphenylphosphine)iridium(I), on hydrogen passivated Si(1 1 1) surfaces to form a self-assembled monolayer (SAM). The iridium complex was synthesized prior to chemical addition, for which modified reaction conditions were chosen. Following addition, the silicon surfaces were characterized with X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The XPS results revealed that the surfaces consisted of the expected elemental percentages and that the iridium has a slightly higher success rate at attaching to oxide-free surfaces. XPS data also strongly indicate that the iridium complex remained intact upon chemisorption and did not decompose during the addition reaction. CV data show a difference between iridium treated surfaces and control samples. Hydrogen passivated wafers with iridium complex were much more conductive than those which were terminated with just an oxide or with an oxide and iridium complex. Furthermore, no free iridium reagent was detected as an additional feature in the current profile, indicating there was no physisorbed layer.     

Excellent passivation of thin silicon wafers by HF‐free hydrogen plasma etching using an industrial ICPECVD tool

In this work, hydrogen plasma etching of surface oxides was successfully accomplished on thin (～100 µm) planar n‐type Czochralski silicon wafers prior to intrinsic hydrogenated amorphous silicon [a‐Si:H(i)] deposition for heterojunction solar cells, using an industrial inductively coupled plasma‐enhanced chemical vapour deposition (ICPECVD) platform. The plasma etching process is intended as a dry alternative to the conventional wet‐chemical hydrofluoric acid (HF) dip for solar cell processing. After symmetrical deposition of an a‐Si:H(i) passivation layer, high effective carrier lifetimes of up to 3.7 ms are obtained, which are equivalent to effective surface recombination velocities of 1.3 cm s^–1 and an implied open‐circuit voltage (V_oc) of 741 mV. The passivation quality is excellent and comparable to other high quality a‐Si:H(i) passivation. High‐resolution transmission electron microscopy shows evidence of plasma‐silicon interactions and a sub‐nanometre interfacial layer. Using electron energy‐loss spectroscopy, this layer is further investigated and confirmed to be hydrogenated suboxide layers. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Ultrastable Perovskite–Zeolite Composite Enabled by Encapsulation and In Situ Passivation

Metal halide perovskites have been widely applied in optoelectronic fields, but their poor stability hinders their actual applications. A perovskite–zeolite composite was synthesized via in situ growth in air from aluminophosphate AlPO-5 zeolite crystals and perovskite nanocrystals. The zeolite matrix provides quantum confinement for perovskite nanocrystals, achieving efficient green emission, and it passivates the defects of perovskite by H-bonding interaction, which leads to a longer lifetime compared to bulk perovskite film. Furthermore, the AlPO-5 zeolite also acts as a protection shield and enables ultrahigh stability of perovskite nanocrystals under 150 °C heat stress, under a 15-month long-term ambient exposure, and even in water for more than 2 weeks, respectively. The strategy of in situ passivation and encapsulation for the perovskite@AlPO-5 composite was amenable to a range of perovskites, from MA- to Cs-based perovskites. Benefiting from high stability and photoluminescence performance, the composite exhibits great potential to be virtually applied in light-emitting diodes (LEDs) and backlight displays.     

Reducing Detrimental Defects for High‐Performance Metal Halide Perovskite Solar Cells

In several photovoltaic (PV) technologies, the presence of electronic defects within the semiconductor band gap limit the efficiency, reproducibility, as well as lifetime. Metal halide perovskites (MHPs) have drawn great attention because of their excellent photovoltaic properties that can be achieved even without a very strict film‐growth control processing. Much has been done theoretically in describing the different point defects in MHPs. Herein, we discuss the experimental challenges in thoroughly characterizing the defects in MHPs such as, experimental assignment of the type of defects, defects densities, and the energy positions within the band gap induced by these defects. The second topic of this Review is passivation strategies. Based on a literature survey, the different types of defects that are important to consider and need to be minimized are examined. A complete fundamental understanding of defect nature in MHPs is needed to further improve their optoelectronic functionalities.     

Regulation of Cathode‐Electrolyte Interphase via Electrolyte Additives in Lithium Ion Batteries

As the power supply of the prosperous new energy products, advanced lithium ion batteries (LIBs) are widely applied to portable energy equipment and large‐scale energy storage systems. To broaden the applicable range, considerable endeavours have been devoted towards improving the energy and power density of LIBs. However, the side reaction caused by the close contact between the electrode (particularly the cathode) and the electrolyte leads to capacity decay and structural degradation, which is a tricky problem to be solved. In order to overcome this obstacle, the researchers focused their attention on electrolyte additives. By adding additives to the electrolyte, the construction of a stable cathode‐electrolyte interphase (CEI) between the cathode and the electrolyte has been proven to competently elevate the overall electrochemical performance of LIBs. However, how to choose electrolyte additives that match different cathode systems ideally to achieve stable CEI layer construction and high‐performance LIBs is still in the stage of repeated experiments and exploration. This article specifically introduces the working mechanism of diverse electrolyte additives for forming a stable CEI layer and summarizes the latest research progress in the application of electrolyte additives for LIBs with diverse cathode materials. Finally, we tentatively set forth recommendations on the screening and customization of ideal additives required for the construction of robust CEI layer in LIBs. We believe this minireview will have a certain reference value for the design and construction of stable CEI layer to realize desirable performance of LIBs.