Fast Modulation of d-Band Holes Quantity in the Early Reaction Stages for Boosting Acidic Oxygen Evolution

Synthesis of highly active and durable oxygen evolution reaction (OER) catalysts applied in acidic water electrolysis remains a grand challenge. Here, we construct a type of high-loading iridium single atom catalysts with tunable d-band holes character (h-HL−Ir SACs, ∼17.2 wt % Ir) realized in the early OER operation stages. The in situ X-ray absorption spectroscopy reveals that the quantity of the d-band holes of Ir active sites can be fast increased by 0.56 unit from the open circuit to a low working potential of 1.35 V. More remarkably, in situ synchrotron infrared and Raman spectroscopies demonstrate the quick accumulation of *OOH and *OH intermediates over holes-modulated Ir sites in the early reaction voltages, achieving a rapid OER kinetics. As a result, this well-designed h-HL−Ir SACs exhibits superior performance for acidic OER with overpotentials of 216 mV @10 mA cm⁻² and 259 mV @100 mA cm⁻², corresponding to a small Tafel slope of 43 mV dec⁻¹. The activity of catalyst shows no evident attenuation after 60 h operation in acidic environment. This work provides some useful hints for the design of superior acidic OER catalysts.     

Co−Co Dinuclear Active Sites Dispersed on Zirconium-doped Heterostructured Co9S8/Co3O4 for High-current-density and Durable Acidic Oxygen Evolution

Developing cost-effective and sustainable acidic water oxidation catalysts requires significant advances in material design and in-depth mechanism understanding for proton exchange membrane water electrolysis. Herein, we developed a single atom regulatory strategy to construct Co−Co dinuclear active sites (DASs) catalysts that atomically dispersed zirconium doped Co₉S₈/Co₃O₄ heterostructure. The X-ray absorption fine structure elucidated the incorporation of Zr greatly facilitated the generation of Co−Co DASs layer with stretching of cobalt oxygen bond and S−Co−O heterogeneous grain boundaries interfaces, engineering attractive activity of significantly reduced overpotential of 75 mV at 10 mA cm⁻², a breakthrough of 500 mA cm⁻² high current density, and water splitting stability of 500 hours in acid, making it one of the best-performing acid-stable OER non-noble metal materials. The optimized catalyst with interatomic Co−Co distance (ca. 2.80 Å) followed oxo-oxo coupling mechanism that involved obvious oxygen bridges on dinuclear Co sites (1,090 cm⁻¹), confirmed by in situ SR-FTIR, XAFS and theoretical simulations. Furthermore, a major breakthrough of 120,000 mA g⁻¹ high mass current density using the first reported noble metal-free cobalt anode catalyst of Co−Co DASs/ZCC in PEM-WE at 2.14 V was recorded.     

Tribo-corrosion behavior of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel

In this investigation , Zn-Ni-Cu and Zn-Ni-Cu-TiB₂ were coated on a mild steel specimen using a high velocity oxy fuel thermal spray (HVOF) process. The surface morphology and coated powder distribution of coated specimens were characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray-Elemental mapping. The pin-on-disc (ASTM G99-17) method was used to examine the wear resistance of the coated and uncoated mild steel specimens. Both coated Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on mild steel saw reduced wear volume loss than uncoated mild steel. The coated samples of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on Mild Steel were put through a scratch test to determine the adhesion strength of the coating with the substrate. The adhesion strength of coated Zn-Ni-Cu and Zn-Ni-Cu TiB2 mild steel was higher than that of untreated mild steel, indicating a solid link between the coating and substrate and minimal delamination. Using the Vickers hardness test to measure the hardness caused by the coating, it was shown that coated samples of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel had significantly higher hardness than uncoated mild steel. Using ASTM G1-03 and ASTM G-31 standards, a 0.2 M HCl immersion cycle test was conducted for 28 days to test the corrosion resistance of coatings in an acidic media (672Hrs). When compared to Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel, the weight loss for the uncoated mild steel was significantly larger. Additionally, XRD examination showed that coated samples had less rust on their surface than uncoated samples. Both Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on Mild Steel were anti-corrosive, as evidenced by increased corrosion potential and reduced corrosion current density when compared to uncoated mild steel, according to electrochemical impedance spectroscopy (EIS)/Tafel study in 0.2 MHCl. The outcomes of each test were very encouraging and demonstrated the durability of these coatings against wear and corrosion.     

碳酸氢盐活化的过氧化氢：一种有机废水处理的新技术

水污染问题已成为影响我国可持续发展的关键问题之一,为有效提高现有污水处理的效率及其回收利用,各种催化氧化技术受到了广泛的关注。目前发展的各类高级氧化技术在实际的应用过程中明显受到了氧化剂的利用率、催化剂的浸出、寿命及成本等问题的严重限制。因此基于新的理念、发展新的催化氧化技术仍然受到广泛的关注。
　　最近几年,利用碳酸氢盐活化过氧化氢,应用于有机废水的降解逐渐受到环境催化领域的关注。碳酸氢盐本身是一种低毒性、广泛存在于环境及生物体系的化学物质,通过它活化过氧化氢产生过碳酸氢盐氧化剂,该氧化剂能够直接氧化有机物。同时,在各种过渡金属催化剂的存在下,通过该过碳酸氢盐可以形成氧化能力更强的各种自由基(如羟基自由基等) 及高价态的过渡金属离子参与有机废水的降解。虽然传统认为碳酸盐及碳酸氢盐对高级氧化法降解有机废水不利,原因是认为它们能捕捉羟基自由基,形成氧化能力更低的碳酸根自由基。现有的研究已充分表明,较低浓度的碳酸氢盐能够加快有机废水的氧化降解,而且通常比单独使用过氧化氢效率更高,这些新的发现已明显突破了传统意义上对碳酸氢盐作用的理解。更为重要的是,在微量碳酸氢盐的存在下,其产生的微碱性环境极大地消除了负载型氧化物催化剂在废水降解过程中的金属离子流失、从而极大地延长了催化剂的寿命。该缺点是各种基于过渡金属氧化物催化剂的高级氧化技术难以广泛推广的关键性挑战,原因是随着氧化降解的进行,废水体系由于有机酸的生成而逐渐酸化,进而引发氧化物催化剂的酸溶而流失。在这点上,碳酸氢盐活化过氧化氢系统由于其天然的微碱性环境体现出了其明显的优势。
　　本文即是在本课题组工作基础上,对该领域内国内外研究进展加以总结,以期获得国内外同行的进一步关注。综述的主要内容包括：(1)碳酸氢氧活化过氧化氢的相关知识介绍,(2)均相碳酸氢氧活化过氧化氢降解有机废水的研究进展,(3)基于金属氧化物催化剂的碳酸氢氧活化过氧化氢降解有机废水的研究进展,和(4)碳酸氢盐在其他高级氧化技术中的应用。虽然基于碳酸氢氧活化过氧化氢降解有机废水的研究还处于早期探索阶段,还有很多基础科学问题如降解机理等值得进一步探索,期望通过该综述的介绍能够让同行对碳酸氢氧活化过氧化氢降解有机废水有一个比较全面的了解,进而推动该研究方向的发展,为有机废水的催化处理提供新的机会。     

晶体硅金刚线切割废料制备高纯氮化硅

以晶体硅金刚线切割废料为原料,通过氮化反应制得氮化硅,既回收了金刚线切割废料,又解决了环境污染的问题。 通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和X射线能量色谱仪(EDS)等技术手段研究了原料经HCl和HF酸洗净化后制备氮化产物的物相组成、组分质量分数和微观形貌的影响。 结果表明,HCl酸洗后切割废料制备的氮化产物中主要物相为Si₂N₂O和Si₃N₄,而HF酸洗后切割废料制备的氮化产物中主要物相为Si₃N₄。 氮化产物中Si₂N₂O的形成与切割废料中SiO₂的质量分数有关,降低原料中SiO₂的质量分数是切割废料经过高温氮化制得氮化硅的前提。     

Anti-Hofmeister series properties found for a polymer having a π electron system and acidic protons

Anti-Hofmeister series properties have been found for a polymer (PVA-T) having a π electron system and acidic protons, which were prepared by introducing trimellitic anhydride to poly(vinyl alcohol) (PVA). Aqueous dispersion of PVA-T became clear in the presence of 1 M Na₂SO₄, a typical kosmotrope, due to dissolution of the solid polymer sample, while the turbidity in the presence of 1 M KSCN, a typical chaotrope, hardly changed. Being consistent to the salt effects, PVA-T hydrogel, which was prepared by chemical cross-linking, showed marked swelling in sulfate solutions, whereas the swelling degree was only marginal in thiocyanates.     

Modelling spur chemistry for alkaline and acidic water at high temperatures

The effect of pH and associated ionic strength on the primary yields in the radiolysis of pressurised water has been assessed by diffusion-kinetic calculations for temperatures in the range 100–300°C. Account has been taken for ionic strength I up to 0.1 mol kg⁻¹, assuming that the counter ions of H⁺ in acid solutions and of OH⁻ in base solutions have unit charge. In acid solutions, the H⁺ ions react with e⁻ _aq. The decrease in G(e⁻ _aq) and the increase in G(H) with decreasing pH becomes substantial for [H⁺] ≥ 1 × 10⁻⁴ m, but the primary yields of oxidising species are almost constant. In alkaline solutions, the OH⁻ anions affect the spur chemistry of radiation-generated protons and hydroxyl radicals for [OH⁻] ≥ 1 × 10⁻⁴ m. The scavenging of H atoms and hydrogen peroxide becomes significant for [OH⁻] ≥ 1 × 10⁻² m. The total yields G(OH) + G(O⁻) and G(H₂O₂) + G(HO₂ ⁻) are independent of base concentration below 0.01 m. In more alkaline solutions, G(OH) + G(O⁻) increases, whereas G(H₂O₂) + G(HO₂ ⁻) decreases with increasing [OH⁻]. Calculations showed the substantial yield of the reaction O⁻ + e⁻ _aq in 0.1 m base solution. Spur chemistry in alkaline hydrogenated water is not affected by the presence of H₂ if less than 0.001 m of hydrogen is added.     

Baeyer-Villiger oxidation of cyclic ketones utilizing potassium peroxydisulfate(K_2S_2O_8) or sodium perborate(NaBO_3) in acidic media

The efficient, green, facile, mild and straightforward conversion procedure for the oxidation of cyclic ketones to lactones at room temperature utilizing potassium peroxydisulfate (K₂S₂O₈) in acidic media is satisfactory to high yields without using traditional chlorinated solvents is reported. This oxidative reagent is cheap and friendly environmental procedure for industrial purposes than use of organic peracids.     

Online process control of acidic texturisation baths with ion chromatography

Etching of silicon with mixtures of hydrofluoric acid and nitric acid is a widely used process in silicon solar cell fabrication. One precondition for an optimized usage of the acidic etching baths is the exact knowledge of the chemical bath composition. In this paper, we investigated a fast and online-capable method for the total analysis of all bath constituents by ion chromatography. The chromatographical system consists of a low-volume injection valve, which injects the concentrated samples directly into the KOH-based eluent. After separation and detection of nitrate and fluoride, a post-column derivatization with sodium molybdate is applied to detect the hexafluorosilicic acid, which enriches in the texturisation bath during the etching process. The results of the presented approach are discussed and compared with already published chromatographical and titration methods found in literature.     

Determination of metals, metalloids and non-volatile ions in airborne particulate matter by a new two-step sequential leaching procedure Part B: Validation on equivalent real samples

Due to the lack of proper standard materials for airborne particulate matter collected on filters, a validation scheme was developed, which is here described, to the aim of testing the application of leaching procedures performing both ions and elemental determinations on real samples of airborne particulate matter collected on filters. The scheme has been developed on a two-step leaching method (extraction in acetate buffer and acid dissolution of residue) previously developed by authors and consists of two series of tests to be run on n pairs of equivalent parallel samples filter-collected. The first series of tests aims to assess on real samples the equivalence between results obtained by the tested procedure with those obtained by the EMEP ions extraction and the EN 12341 standard methods, whereas the second aims to evaluate the reproducibility of analytical results of elemental determination in the leached and dissolved fractions; in the latter case data reliability is also evaluated as a function of the environment-intrinsic variability of real samples.To avoid errors due to sampling differences data from filter pairs were standardized both by gravimetric determination of loaded filters, according to the EN 12341 standard and by the rate [SO₄²⁻]_A/[SO₄²⁻]_B, where [SO₄²⁻] indicate the soluble sulphate concentration in the extract; in the latter case values improved for all elements and in both fractions. Results of equivalence with standard methods and reproducibility tests are evaluated as mean relative percentage differences (Δ%) and percentage elements recoveries (R%). The application of the validation scheme to the two-step leaching method is here discussed for non-volatile ions and for 17 elements detected on 22 pairs of low-volume collected PM₁₀ samples on Teflon filters.