Co1-xS embedded in porous carbon derived from metal organic framework as a highly efficient electrocatalyst for oxygen evolution reaction

Here, we report a two-step conversion method to fabricate a composite of Co_1-xS embedded in porous carbon framework (Co_1-xS@C) derived from metal organic frameworks (MOFs). The as-prepared porous dodecahedron Co_1-xS@C composite catalyst exhibits excellent electrocatalytic performance towards oxygen evolution reaction (OER).     

凝固漂浮有机液滴-分散液液微萃取结合高效液相色谱法同时测定自来水中氯代多环芳烃与多环芳烃

建立了自来水中6种氯代多环芳烃和15种多环芳烃的凝固漂浮有机液滴-分散液液微萃取高效液相色谱分析方法,并探讨了萃取剂种类和用量、分散剂种类和用量、氯化钠含量及涡旋振荡时间等因素对萃取效率的影响。优化后的萃取实验条件为:10μL十二醇为萃取溶剂,500μL甲醇为分散溶剂,6%NaCl,涡旋振荡时间2 min。目标化合物经多环芳烃专用柱(SUPELCOSILTMLC-PAH,150 mm×4.6 mm,5μm)分离后,外标法定量。结果表明,21种目标化合物在一定质量浓度范围内线性良好,相关系数均不低于0.999;在低、中、高3个加标水平下的回收率为70.6%～98.7%,相对标准偏差(RSD)为2.0%～10%;方法的检出限(LOD,S/N=3)为0.000 7～0.009μg/L,定量下限(LOQ,S/N=10)为0.002 2～0.028μg/L。可用于自来水中氯代多环芳烃和多环芳烃的分析检测。     

预嵌锂硬碳和软碳用于锂离子电容器负极的比较研究

锂离子电容器是一种应用前景广阔的电化学储能器件. 目前,活性炭作为锂离子电容器正极被广泛使用. 然而,锂离子电容器负极却有多种不同选择,如硬碳和软碳等碳材料. 本文使用两种具有不同结构和电化学特性的硬碳和软碳材料作为锂离子电容器负极,进行了对比研究. 研究表明,软碳相比于硬碳有更好的电子导电性和更高的可逆容量. 通过在电流范围0.1 ~ 12 A·g^-1下进行充放电测试,分别研究了两种碳基电极在不同涂覆厚度下的倍率性能. 结果显示,硬碳电极在大电流下有更好的倍率特性. 然后,以活性炭为正极,预嵌锂的硬碳和软碳为负极,锂片为锂源和参比电极,分别组装了三电极软包锂离子电容器. 根据三电极充放电测试,分别研究了不同预嵌锂量的硬碳和软碳所组装的锂离子电容器的电化学性能. 结果表明,合适的负极预嵌锂容量可以提升锂电容的能量密度、功率密度和循环稳定性. 最后,大容量硬碳和软碳基软包锂离子电容器被分别组装,软碳基锂电容实现了最高的能量密度21.2 Wh·kg^-1（基于整个器件质量）,硬碳基锂电容实现最高的功率密度5.1 kW·kg^-1.     

基于电化学方法测定饮用水源水中的痕量铜离子

本文建立了一种饮用水源水中痕量溶解态铜离子（Cu²⁺）的定性和定量电化学检测方法. 该方法首先通过电化学循环伏安法于玻碳电极表面制备粒径约为70 nm的金纳米粒子（Au NPs）,然后采用方波阳极溶出伏安法进行待测水样中Cu²⁺的定性定量分析. 研究结果表明,对于标准溶液,方法的检出限为1.3μg·L^-1,线性范围在2 ~ 50μg·L^-1之间,常见重金属离子对其定性定量分析几无影响. 在此基础上,将该方法应用于福建省重要的饮用水源水--闽江中游水样中Cu²⁺的含量分析,所得测试结果与国家标准方法（石墨炉原子吸收光谱法）无显著性差异,标准偏差在20%以内. 本方法具有电极制备简单、测定成本低以及分析快速等优点,进一步优化电极制备方法以提高方法的重现性和定量准确度,将可望用于现场测定各种饮用水源水中的痕量溶解态Cu²⁺.     

Preparation of glycerol plasticized chitosan films using AlCl3·6H2O as the solvent: optical,crystalline, mechanical and barrier properties

Chitosan films plasticized with the complex of AlCl₃·6H₂O and glycerol were prepared by using AlCl₃·6H₂O as the solvent. The effect of AlCl₃·6H₂O and glycerol complex with Chitosan was studied by SEM, XRD, TGA, and tensile testing. The complex would increase the water resistance and destroy the crystals of chitosan film. The TGA results proved that the chitosan film plasticized with the complex showed higher thermal stability at the temperature below 200?°C than pure chitosan film. With the addition of the complex of AlCl₃·6H₂O and glycerol, the tensile strength of chitosan film decreased and the elongation at break increased.     

The Advanced Multi‐functional Electrocatalyst Efficiently Built from Multi‐integrated Sites for Overall Water Splitting and Rechargeable Zinc‐air Battery

Exploration of cost‐effective, high‐performance and durable multifunctional electrocatalysts is of significant importance for renewable energy conversion and storage. In this work, a simple strategy is developed to tailor the nickel metal with the collaboration of nitrogen‐doped graphene and single‐walled carbon nanotubes. The resulted nickel catalyst exhibits superior trifunctional activities for oxygen evolution, hydrogen evolution and oxygen reduction reactions in the same electrolyte, even comparable to commercial Pt/C and RuO₂ respectively, which can be attributed to the synergistic advantages between nickel, nitrogen and carbon, mainly including abundant integrated active sites achieved by the irregular charge distribution among C?N and Ni?N coupling centers. Such remarkable effects on trifunctional catalysis elicit the efficient overall water splitting, and endow the assembled zinc‐air battery with a good performance. These highlight the metallic nickel as an advanced multifunctional electrocatalysts with integrated sites developed from the collaboration of two different carbon nanomaterials.     

Electroanalysis of Bisphenols A,F, and Z Using Graphene Based Stochastic Microsensors

Two stochastic microsensors based on immobilization of the complex between protoporphyrin IX and cobalt on nanographene paste and on the reduced graphene oxide paste were proposed for the simultaneous identification and quantification of bisphenols A (BPA), F (BPF) and Z (BPZ) from water samples. The signatures obtained for the BPA, BPF, and BFZ when both stochastic microsensors were used shown that the microsensors can be used for the discrimination between the three bisphenols in water samples. Very low limits of determination were obtained for the three bisphenols: 1fmol/L for BPA and BPF when the microsensor based on the immobilization of the complex between protoporphyrin IX and cobalt on nanographene paste was used, and 10fmol/L for BPZ when the microsensor based on the immobilization of the complex between protoporphyrin IX and cobalt on reduced graphene oxide paste was used. The linear concentration ranges covered by the proposed stochastic microsensors were: between 10^?15 and 10^?5 mol/L for BPA, between 10^?15 and 10^?7 mol/L for BPF, and between 10^?13 and 10^?10 mol/L for BPZ. The recoveries of the bisphenols in water samples were higher than 99.50 %, with RSD values lower than 1.00 %.     

General π‐Electron‐Assisted Strategy for Ir,Pt, Ru,Pd, Fe,Ni Single‐Atom Electrocatalysts with Bifunctional Active Sites for Highly Efficient Water Splitting

Both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are crucial to water splitting, but require alternative active sites. Now, a general π‐electron‐assisted strategy to anchor single‐atom sites (M=Ir, Pt, Ru, Pd, Fe, Ni) on a heterogeneous support is reported. The M atoms can simultaneously anchor on two distinct domains of the hybrid support, four‐fold N/C atoms (M@NC), and centers of Co octahedra (M@Co), which are expected to serve as bifunctional electrocatalysts towards the HER and the OER. The Ir catalyst exhibits the best water‐splitting performance, showing a low applied potential of 1.603 V to achieve 10 mA cm^?2 in 1.0 m KOH solution with cycling over 5 h. DFT calculations indicate that the Ir@Co (Ir) sites can accelerate the OER, while the Ir@NC₃ sites are responsible for the enhanced HER, clarifying the unprecedented performance of this bifunctional catalyst towards full water splitting.     

The Surface Activity of the Hydrated Proton Is Substantially Higher than That of the Hydroxide Ion

The behavior of hydroxide and hydrated protons, the auto‐ionization products of water, at surfaces is important for a wide range of applications and disciplines. However, it is unknown at which bulk concentration these ions start to become surface active at the water–air interface. Here, we report changes in the D₂O–air interface in the presence of excess D⁺_hyd/OD^?_hyd determined using surface‐sensitive vibrational sum‐frequency generation (SFG) spectroscopy. The onset of the perturbation of the D₂O surface occurs at a bulk concentration as low as 2.7±0.2 mm D⁺_hyd. In contrast, a concentration of several hundred mm OD^?_hyd is required to change the D₂O surface. The hydrated proton is thus orders of magnitude more surface‐active than hydroxide at the water–air interface.