Degradation of rhodamine B photocatalyzed by Eu-doped CdS nanowires illuminated by visible radiation

CdS nanowires doped with different contents of Eu dopant were synthesized by solvothermal method. XRD, SEM, TEM and Raman analyses certified that the as-synthesized samples were hexagonal CdS uniform nanowires. The pure CdS nanowires were 1–3 ?μm long and 80 ?nm diameter with the 1st and 2nd order longitudinal phonon modes at 298 and 594 ?cm^?1. The 3% Eu-doped CdS wires were 800 ?nm–2.5 ?μm long and 75 ?nm diameter with the 1st and 2nd order longitudinal phonon modes at 296 and 593 ?cm^?1. CdS nanowires grew along the [001] direction due to the surface energy effect. The photocatalytic properties of CdS and Eu-doped CdS nanowires were investigated for the degradation of rhodamine B (RhB) illuminated by visible radiation. In this research, Eu dopant played the role in promoting the photocatalytic kinetics because Eu³⁺ ions act as an electron acceptor to promote charge separation and photocatalytic activity. Both ^●OH and ^●O₂^? were the main active radicals used to transform RhB molecules into CO₂, H₂O and other intermediates.     

One-dimensional displacement of active matter on curved substrates

We analytically find the diffusion of overdamped active Brownian particles (ABPs) constrained to move along curved one-dimensional channels. The autonomous motion of these particles is achieved by a projection of their internal propulsion force along the channels' long section. In particular, the diffusion of ABPs moving on one-dimensional channels with a form of a circle, an ellipse, and a limacon of second order is analysed. To characterise the effect of substrate's geometry and self-propulsion on their diffusion, analytical expressions for the ABPs short- and long-time variances, as well as their steady angular probability density functions are offered. Curvature effects are found to reduce the time an ABP reaches its steady state. Our theoretical results are validated using Brownian dynamics simulations. This model may be relevant for experiments dealing with catalytic driven systems, bacteria, and tumour cell dispersion in one-dimensional channels.     

Recent advances on the use of active anodes in environmental electrochemistry

Active anodes, especially those consisting of metal mixed oxides (MMOs) containing Ru and/or Ir oxides, have been applied in the treatment of wastewater, especially when chloride ions are present. Their characteristics continuously drive the study of applications of these materials, be they in the degradation of different organic molecules, the preparation of new electrode materials and in the association of various processes to increase pollutant removal. Thus, this brief review aims to present some of the recent advances in the application of active anode materials in environmental electrochemistry. Focussing on the 2018–2020 period, it is possible to note many applied studies, using commercially available materials, covering a wide range of target pollutants. Still other studies aim to modify the catalyst surfaces to increase the mineralization capacity, and the use of these anodes in the production of free chlorine species to mediate indirect organic reduction is observed.     

Solid Interhalogen Compounds with Effective Br0 Fixing for Stable High-energy Zinc Batteries

Though massive efforts have been devoted to exploring Br-based batteries, the highly soluble Br₂/Br₃⁻ species causing rigorous “shuttle effect”, leads to severe self-discharge and low Coulombic efficiency. Conventionally, quaternary ammonium salts such as methyl ethyl morpholinium bromide (MEMBr) and tetrapropylammonium bromide (TPABr) are used to fix Br₂ and Br₃⁻, but they occupy the mass and volume of battery without capacity contribution. Here, we report an all-active solid interhalogen compound, IBr, as a cathode to address the above challenges, in which the oxidized Br⁰ is fixed by iodine (I), thoroughly eliminating cross-diffusing Br₂/Br₃⁻ species during the whole charging and discharging process. The Zn||IBr battery delivers remarkably high energy density of 385.8 Wh kg⁻¹, which is higher than those of I₂, MEMBr₃, and TPABr₃ cathodes. Our work provides new approaches to achieve active solid interhalogen chemistry for high-energy electrochemical energy storage devices.     

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.     

纳米SiO_2表面基团在MMA原位本体聚合中的阻缓聚作用

分别以3-(甲基丙烯酰氧)丙基三甲氧基硅烷(MPS)和辛基三甲氧基硅烷(OTMS)为活性和惰性硅烷的代表,对SiO2进行不同锚固密度的表面修饰,并以改性SiO2的甲基丙烯酸甲酯(MMA)单体分散液为原料,通过原位本体聚合制得一系列SiO2含量不同的高分散性SiO2/PMMA复合材料.考察SiO2表面基团活性程度和SiO2含量对聚合反应动力学、基体聚合物分子量以及复合材料硬度的影响,探究修饰状态不同SiO2在本体自由基聚合中的作用机制.发现SiO2表面硅羟基及其锚固MPS的活性双键会对聚合反应起阻缓聚作用,进而会显著降低基体聚合物的分子量及复合材料的硬度.而惰性硅烷OTMS对SiO2表面的锚固则会消耗SiO2表面硅羟基、并屏蔽其影响,因而随着OTMS锚固密度的提高,基体分子量和复合材料硬度均会随之提高,特别是当表面修饰达到饱和状态时,SiO2的阻缓聚作用已可忽略.     

氧化钛负载脱硝催化剂的碱中毒过程：氧化钒的保留和氧化钨的牺牲

V2O5-WO3/TiO2催化剂目前已广泛用于电厂和工业锅炉燃烧废气脱硝,但燃烧原料煤及石油中含有的杂质元素碱金属与碱土金属元素可吸附在催化剂上,不仅会减少催化剂酸性位的数量,还会与催化活性元素结合生成惰性物种,导致催化剂失活。因此,已有许多有关钒钨钛催化剂碱中毒的研究,从催化剂的氧化还原能力、酸性位损失及表面孔结构等方面进行了讨论。但这些研究大多集中在碱中毒对活性组分V2O5的影响及中毒催化剂的活性变化,很少涉及催化剂中WO3的作用,也缺乏有关不同活性元素与钾盐反应的实验证据。本文采用过量浸渍法制备了不同钒和钨含量的钒钨钛催化剂,研究了氯化钾对其氨法选择性催化还原(NH3-SCR)活性的失活效应。利用感应耦合等离子体、N2吸附、拉曼光谱、H2程序升温还原、NH3吸附红外光谱和NH3氧化活性等手段对新鲜和中毒催化剂的性质进行了表征,特别探讨了V2O5和WO3对催化剂抗碱中毒能力的贡献。
　　催化剂活性测试结果表明, V2O5含量越高,活性温度窗口越宽,而且含有WO3的三元催化剂活性高于V2O5/TiO2二元催化剂。催化剂的BET比表面积和孔结构取决于TiO2载体,随活性组分配比变化不大,说明催化剂物理结构性质并非影响活性的主要因素。原位红外光谱及H2程序升温还原测试结果表明,随V2O5含量提高,催化剂表面Br?nsted酸性位数量及氧化还原能力提高。作为反应的主要活性物种, V2O5在碱中毒处理后变成惰性的偏钒酸钾KVO3,使催化剂中Br?nsted酸性位减少,热稳定性下降,并削弱了催化剂的氧化还原能力,因此低钒含量的催化剂容易严重中毒失活。在高钒负载量(3%)时,部分V2O5在碱中毒后得以保留,从而使催化剂保持了一定的脱硝催化活性。
　　另外, WO3能给催化剂表面提供热稳定的酸性位,虽然WO3自身的氧化还原能力差,但其能改善V2O5的分散性,从而提高V2O5-WO3/TiO2催化剂的活性。除此之外, WO3在催化剂碱中毒过程中还能扮演牺牲剂,与钾反应生成钨酸钾(K2WO4),即在V2O5与钾离子结合形成KVO3的同时,部分WO3也会与钾反应形成K2WO4,可以使三元催化剂保留更多的活性V物种。因此,在所研究的催化剂中,高钒负载量的V2O5-WO3/TiO2催化剂表现出最好的抗碱中毒能力。
　　活性影响因素分析表明,对于新鲜催化剂,其表面吸附的NH3量足够多,催化剂活性与表面酸性相关度不大,脱硝效率主要取决于催化剂的氧化还原能力。但是,对于碱中毒处理后的催化剂,其表面吸附NH3的能力大大削弱,这时脱硝效率除了受催化剂氧化还原能力影响,在很大程度上也依赖于催化剂的表面酸性。     

Active learning for OPM in FMF systems

Optical performance monitoring (OPM) is essential to guarantee the robust and reliable operation of few-mode fiber (FMF)-based transmission. The available OPM methods including the analytical models such as the enhanced Gaussian noise model provide high accuracy along with high computational complexity which makes them improper for real-time implementations. As an alternative approach, machine learning (ML)-based OPM removes this barrier at the cost of leveraging a large training dataset. However, generating a field or synthetic dataset for FMF-based transmission is very hard and time-consuming. As a specific ML deployment, active learning (AL) is designed to work with a small training dataset, therefore, in this paper, we employ AL for OPM in FMF-based transmission. Results indicate that the proposed AL-based OPM can properly estimate the generalized signal-to-noise ratio by using a very small training dataset and achieve the root mean squared error similar to that obtained by working on large training datasets.     

Engineering shapes of active colloids for tunable dynamics

Active particles can autonomously propel and have the tendency to organize into high-order ensembles and phases that evolve and reconfigure. They have emerged as a focused subject in contemporary colloid science, holding great promise in advancing fields, such as cargo delivery, sensing, micromachinery and microrobotics, and materials science. Realization of the full potentials of active particles requires delicate control of their dynamics in propulsion and assembly, which is challenging due to the out-of-equilibrium nature of such systems. Recently, systematically engineered colloidal shapes have been exploited as an effective means to tune and even program the dynamic behaviors of active particles. Various anisotropic particles, with controlled geometries and possessing either homogeneous or heterogeneous composition, have been fabricated, regulating how particles actively propel, interact, and assemble under several chemical and physical stimuli. In this paper, we provide an overview of these progresses. We also briefly discuss our view on the future directions and challenges.     

A fresh view on phoresis and self-phoresis

Phoresis, a classic example of particle transport driven by thermodynamic gradients, is enjoying a resurgent research interest motivated both by technological developments and by its relevance to the motility of chemically active particles. Here we succinctly review, using the case of chemophoresis (also called diffusiophoresis), the general framework of phoresis and self-phoresis formulated as a Stokes-flow problem for a liquid solution (solvent and solute) maintained out of thermodynamic equilibrium by solute gradients. Within the constraints of local equilibrium, we discuss the simplest extension of the theory in order to account for correlations in the fluid. We show that this leads to a shift from the paradigm based on the ideal case, in that self-phoresis can no longer be represented as phoresis in a self-generated composition gradient. Our review concludes with a concise overview of a few directions which we think hold the potential to reveal a rich behavior in future investigations.