Miniaturized electrochemical sensors and their point-of-care applications

Most of the current analytical methods depend largely on laboratory-based analytical techniques that require expensive and bullky equipment,potentially incur costly testing,and involve lengthy detection processes.With increasing requirements for point-of-care testing(POCT),more attention has been paid to miniaturized analytical devices.Miniaturized electrochemical(MEC)sensors,including different material-based MEC sensors(such as DNA-,paper-,and screen electrode-based),have been in strong demand in analytical science due to their easy operation,portability,high sensitivity,as well as their short analysis time.They have been applied for the detection of trace amounts of target through measuring changes in electrochemical signal,such as current,voltage,potential,or impedance,due to the oxidation/reduction of chemical/biological molecules with the help of electrodes and electrochemical units.MEC sensors present great potential for the detection of targets including small organic molecules,metal ions,and biomolecules.In recent years,MEC sensors have been broadly applied to POCT in various fields,including health care,food safety,and environmental monitoring,owing to the excellent advantages of electrochemical(EC)technologies.This review summarized the state-of-the-art advancements on various types of MEC sensors and their applications in POCT.Furthermore,the future perspectives,opportunities,and challenges in this field are also discussed.     

Machine Learning towards Screening Solid-state Lithium Ion Conductors

Machine learning is an emerging method to discover new materials with specific characteristics.An unsupervised machine learning research is highlighted to discover new potential lithium ionic conductors by screening and clustering lithium compounds,providing inspirations for the development of solid-state electrolytes and practical batteries.     

Surface defect-rich ceria quantum dots anchored on sulfur-doped carbon nitride nanotubes with enhanced charge separation for solar hydrogen production

Designing defect-engineered semiconductor heterojunctions can effectively promote the charge carrier separation.Herein,novel ceria(CeO2) quantum dots(QDs) decorated sulfur-doped carbon nitride nanotubes(SCN NTs) were synthesized via a thermal polycondensation coupled in situ depositionprecipitation method without use of template or surfactant.The structure and morphology studies indicate that ultrafine CeO2 QDs are well distributed inside and outside of SCN NTs offering highly dispersed active sites and a large contact interface between two components.This leads to the promoted formation of rich Ce³⁺ ion and oxygen vacancies as confirmed by XPS.The photocatalytic performance can be facilely modulated by the content of CeO2 QDs introduced in SCN matrix while bare CeO2 does not show activity of hydrogen production.The optimal catalyst with 10% of CeO2 loading yields a hydrogen evolution rate of 2923.8 μmol h-1 g-1 under visible light,remarkably higher than that of bare SCN and their physical mixtures.Further studies reveal that the abundant surface defects and the created 0 D/1 D junctions play a critical role in improving the separation and transfer of charge carriers,leading to superior solar hydrogen production and good stability.     

Superfast and solvent-free core-shell assembly of sulfur/carbon active particles by hail-inspired nanostorm technology for high-energy-density Li-S batteries

The demand on low-carbon emission fabrication technologies for energy storage materials is increasing dramatically with the global interest on carbon neutrality.As a promising active material for metal-sulfur batteries,sulfur is of great interest due to its high-energy-density and abundance.However,there is a lack of industry-friendly and low-carbon fabrication strategies for high-performance sulfur-based active particles,which,however,is in critical need by their practical success.Herein,based on a hail-inspired sulfur nano-storm(HSN)technology developed in our lab,we report an energy-saving,solvent-free strategy for producing core-shell sulfur/carbon electrode particles(CNT@AC-S)in minutes.The fabrication of the CNT@AC-S electrode particles only involves low-cost sulfur blocks,commercial carbon nanotubes(CNT)and activated carbon(AC)micro-particles with high specific surface area.Based on the above core-shell CNT@AC-S particles,sulfur cathode with a high sulfur-loading of 9.2 mg cm^-2 delivers a stable area capacity of 6.6 mAh cm^-2 over 100 cycles.Furthermore,even for sulfur cathode with a super-high sulfur content(72 wt%over the whole electrode),it still delivers a high area capacity of 9 mAh cm^-2 over50 cycles in a quasi-lean electrolyte condition.In a nutshell,this study brings a green and industryfriendly fabrication strategy for cost-effective production of rationally designed S-rich electrode particles.     

Unraveling the stabilization mechanism of solid electrolyte interface on ZnSe by rGO in sodium ion battery

Transition metal selenides have been widely studied as anode materials of sodium ion batteries(SIBs),however,the investigation of solid-electrolyte-interface(SEI)on these materials,which is critical to the electrochemical performance of SIBs,remains at its infancy.Here in this paper,ZnSe@C nanoparticles were prepared from ZIF-8 and the SEI layers on these electrodes with and without reduced graphene oxide(rGO)layers were examined in details by X-ray photoelectron spectroscopies at varied charged/discharged states.It is observed that fast and complicated electrolyte decomposition reactions on ZnSe@C leads to quite thick SEI film and intercalation of solvated sodium ions through such thick SEI film results in slow ion diffusion kinetics and unstable electrode structure.However,the presence of rGO could efficiently suppress the decomposition of electrolyte,thus thin and stable SEI film was formed.ZnSe@C electrodes wrapped by rGO demonstrates enhanced interfacial charge transfer kinetics and high electrochemical performance,a capacity retention of 96.4%,after 1000 cycles at 5 A/g.This study might offer a simple avenue for the designing high performance anode materials through manipulation of SEI film.     

CXN天然沸石的研究2: 吸附性质

采用N~2,NH~3,CO~2,乙烯,丙烯,水,甲醇,乙醇,丙醇等作为吸附剂,研究了由我国CXN天然沸石改性制得的H-STI和Na-STI沸石的吸附性质,H-STI和Na-STI沸石的BET表面积及微孔孔体积约为420m^2/g和0.20m^3/g。根据NH~3和CO~2在H-STI沸石上的吸附等温线计算得到它们的吸附热分别为44.8和26.5kJ/mol。乙烯,丙烯,甲醇,乙醇,丙醇等在Na-STI沸石上的吸附等温线表明该沸石对有机分子的吸附具有链长选择性。在低分压下水相对于甲醇的吸附量表明沸石具有一定的疏水性质。     

常温常湿条件下Au/MeO~x催化剂上CO氧化性能

利用共沉淀法制备了Au/MeO~x催化剂(Me=Al,Co,Cr,Cu,Fe,Mn,Ni,Zn)。在常温常湿条件下,考察了不同氧化物负载的金基催化剂的CO氧化性能。结果表明,氧化物种类对催化剂的活性和稳定性均有较大的影响。Cu,Mn,Cr等氧化物负载的金基催化剂的活性较差,而Zn,Fe,Co,Ni,Al等金属氧化物负载的金基催化剂可将CO完全氧化,又具有一定的稳定性,在相同反应条件下,CO完全转化时的稳定性顺序为Au/ZnO>Au/α-Fe~2O~3>Au/Co~3O~4>Au/γ-Al~2O~3≈Au/NiO。还发现水对Au/MnO~x催化剂的活性和稳定性有负作用,而对180℃焙烧制备的Au/ZnO-180催化剂的活性和稳定性均有明显的湿度增强作用。     

Regulation of carbon distribution to construct high-sulfur-content cathode in lithium-sulfur batteries

Lithium-sulfur(Li-S)battery is regarded as one of the most promising next-generation energy storage systems due to the ultra-high theoretical energy density of 2600 Wh kg^-1.To address the insulation nature of sulfur,nanocarbon composition is essential to afford acceptable cycling capacity but inevitably sacrifices the actual energy density under working conditions.Therefore,rational structural design of the carbon/sulfur composite cathode is of great significance to realize satisfactory electrochemical performances with limited carbon content.Herein,the cathode carbon distribution is rationally regulated to construct high-sulfur-content and high-performance Li-S batteries.Concretely,a double-layer carbon(DLC)cathode is prepared by fabricating a surface carbon layer on the carbon/sulfur composite.The surface carbon layer not only provides more electrochemically active surfaces,but also blocks the polysulfide shuttle.Consequently,the DLC configuration with an increased sulfur content by nearly 10 wt%renders an initial areal capacity of 3.40 mAh cm^-2 and capacity retention of 83.8%during 50 cycles,which is about two times than that of the low-sulfur-content cathode.The strategy of carbon distribution regulation affords an effective pathway to construct advanced high-sulfur-content cathodes for practical high-energy-density Li-S batteries.     

Boost oxygen reduction reaction performance by tuning the active sites in Fe-N-P-C catalysts

Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction(ORR)and replace Pt catalysts in fuel cells and metal-air batteries.However,it remains a challenge to increase the number of atomically dispersed active sites on these catalysts.Here we report a highly efficient impregnation-pyrolysis method to prepare effective ORR electrocatalysts with large amount of atomically dispersed Fe active sites from biomass.Two types of active catalyst centers were identified,namely atomically dispersed Fe sites and Fe_xP particles.The ORR rate of the atomically dispersed Fe sites is three orders of magnitude higher than it of Fe_xP particles.A linear correlation between the amount of the atomically dispersed Fe and the ORR activity was obtained,revealing the major contribution of the atomically dispersed Fe to the ORR activity.The number of atomically dispersed Fe increases as the Fe loading increased and reaching the maximum at 1.86 wt%Fe,resulting in the maximum ORR rate.Optimized Fe-N-P-C complex catalyst was used as the cathode catalyst in a homemade Zn-air battery and good performance of an energy density of 771 Wh kgZn^-1,a power density of 92.9 m W cm^-2 at 137 m A cm^-2 and an excellent durability were exhibited.     

The pseudocapacitance mechanism of graphene/CoAl LDH and its derivatives:Are all the modifications beneficial?

Cobalt-Aluminum layered double hydroxide(CoAl LDH) is a hopeful electrode material due to the advantage of easy modifiability for preparing LDH-based derivatives.However,there is short of modification methods to prepare the Co-based derivatives from CoAl LDH and also short of an intuitive perspective to analyze the pseudocapacitance mechanism of CoAl LDH and its derivatives.Herein,Graphene/CoAl LDH and its derivatives including Graphene/CoS,Graphene/CoS-1,Graphene/CoOOH,Graphene/CoP were prepared by reasonably using alkali etching treatment,sulfofication and phosphorization.The specific capacitance of Graphene/CoAl LDH,Graphene/CoS,Graphene/CoS-1,Graphene/CoOOH,Graphene/CoP at1 A g^-1 are 260.7,371.3,440.8,61.4 and 122.2 F g^-1,especially.The pseudocapacitance mechanism of Graphene/CoAl LDH and its derivatives was analyzed.Due to the positive effect of sulfofication on the electrical conductivity of GO and cobalt sulfide,the Graphene/CoS and Graphene/CoS-1 exhibit the optimal electrochemical performance and superior rate capability.In addition,due to the repulsion effect between Graphene and OH-,the Graphene/CoAl LDH exhibits optimal cycling stability of 224.1% capacitance retention after 20000 cycles.Besides,the reason of terrible specific capacitance of Graphene/CoOOH is that the presence of H bond in interlayer of CoOOH inhibits the interaction between Co3+ and OHspecies.Hence,not all modifications will increase the specific capacitance of the electrode materials.Overall,this work provides us with a detailed analysis of the electrochemical mechanism and correlation of CoAl LDH and its derivatives from the perspective of crystal structure and composition.     

定量的复合金属锂作为三维泡沫锂电极用于锂电池的研究

金属锂作为电池的负极材料具有极高的比容量和极低的氧化还原电位,能够显著提升电池的能量密度。然而,金属锂负极在实际应用中所面临的主要问题是锂枝晶、界面副反应和电极体积变化大的难题。在本文中,我们提出了一种通过将定量的金属锂与三维骨架进行复合形成三维泡沫锂负极的策略,并利用三维泡沫锂来抑制锂枝晶的生长和缓解电极的体积变化。因此,三维泡沫锂电极有利于金属锂负极的高效利用,并能借助其与平面锂箔相比更高的比表面积和更多的反应位点来提升电池的倍率性能。因此,通过采用三维泡沫锂,对称电池的循环寿命和倍率性能都得到了有效的提升。EIS数据结果表明,三维泡沫锂能够减小对称电池的电荷转移阻抗。而且,将三维泡沫锂作为负极组装的LTO全电池,与锂箔作为负极相比,循环1000周平均放电比容量从65 mAh·g^-1提升至121 mAh·g^-1。     

二次锂离子电池正极活性材料—LiCoO_2制备研究进展

本文简单对比了高温相 LiCoO2和低温相 LiCoO2的结构和电化学性能的差别，详细介绍了 LiCoO2的各种合成方法并评述了不同合成方法、反应条件对 LiCoO2结构、形貌及电化学性能的影响，并提出了今后研究的方向。     

Selectivity of a Lithium‐Recovery Process Based on LiFePO4

The demand for lithium will increase in the near future to 713,000 tonnes per year. Although lake brines contribute to 80% of the production, existing methods for purification of lithium from this source are expensive, slow, and inefficient. A novel electrochemical process with low energy consumption and the ability to increase the purity of a brine solution to close to 98% with a single‐stage galvanostatic cycle is presented.     

Formation and Thermal Decomposition of Gallium Oxynitride Compounds

The formation of a previously unknown crystalline phase was observed in the system Li–Ga–N–O. During the reactions of Ga₂O₃ with Li₃N and of LiGaO₂ with Li₃N, a new compound with the stoichiometry Li₄GaNO₂ was formed. The stages in thermal decomposition of the new phase were determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrochemically fabricated polypyrrole-cobalt-oxygen coordination complex as high-performance lithium-storage materials

Current lithium-ion battery (LIB) technologies are all based on inorganic electrode materials, though organic materials have been used as electrodes for years. Disadvantages such as limited thermal stability and low specific capacity hinder their applications. On the other hand, the transition metal oxides that provide high lithium-storage capacity by way of electrochemical conversion reaction suffer from poor cycling stability. Here we report a novel high-performance, organic, lithium-storage material, a polypyrrole-cobalt-oxygen (PPy-Co-O) coordination complex, with high lithium-storage capacity and excellent cycling stability. Extended X-ray absorption fine structure and Raman spectroscopy and other physical and electrochemical characterizations demonstrate that this coordination complex can be electrochemically fabricated by cycling PPy-coated Co(3)O(4) between 0.0 V and 3.0 V versus Li(+)/Li. Density functional theory (DFT) calculations indicate that each cobalt atom coordinates with two nitrogen atoms within the PPy-Co coordination layer and the layers are connected with oxygen atoms between them. Coordination weakens the C-H bonds on PPy and makes the complex a novel lithium-storage material with high capacity and high cycling stability.     

全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量

采用全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量,用盐酸标准溶液进行滴定,考虑自动电位滴定仪的灵敏性和准确度,通过多次对比实验,确定了仪器的最佳工作参数、滴定剂浓度和样品称样量等滴定条件;对两个不同品位试样分别进行了11次平行测定,相对标准偏差(RSD)均小于1%。在碳酸锂试样中加入基准物质无水碳酸钠进行碳酸根的加标回收实验,碳酸根的加标回收率在99.4%~100%。与传统的酸碱滴定法相比,全自动电位滴定法方便、快捷,同时方法测定结果准确、可靠、精密度高,适合大批量样品快速分析。     

全自动电位滴定法测定锂电池原料碳酸锂中碳酸锂的含量

采用全自动电位滴定法测定锂电池原料碳酸锂中碳酸锂的含量,用盐酸标准溶液进行滴定,考虑自动电位滴定仪的灵敏性和准确度,通过多次对比实验,确定了仪器的最佳工作参数、滴定剂浓度和样品称样量等滴定条件;对2个不同品味试样分别进行了11次平行测定,相对标准偏差（RSD）均小于 1%。在碳酸锂试样中加入基准物质无水碳酸钠进行碳酸根的加标回收实验,碳酸根的加标回收率在99.4%～100.2%之间。与传统的酸碱滴定法相比,全自动电位滴定法方便、快捷,同时该方法测定结果准确、可靠、精密度高,适合大批量快速分析样品。     

Electrochemistry of a lithium electrode in lithium polysulfide solutions

The effect of lithium polysulfides on the cycling of a lithium electrode and the corrosion rate of lithium cathodic deposits in sulfolane electrolytes is studied. Lithium polysulfides are found to affect the shape of polarization curves, the overpotential of electrode processes, and the cycling time. The presence of lithium polysulfides in electrolyte systems increases the cycling time of a lithium electrode and positively affects the quality of lithium cathodic deposits. A suggested reason for the positive effect of lithium polysulfides is the appearance of a surface film on metallic lithium: this film has quite high protective properties but does not inhibit electrochemical processes.     

Formation and Thermal Decomposition of Indium Oxynitride Compounds

During the reactions of lithium oxide with indium nitride, lithium nitride with indium oxide, and lithium nitride with lithium indate LiInO2, the formation of a previously unknown crystalline phase, of composition Li4InNO2, was observed. The course of thermal decomposition of the new compound was determined. This revised version was published online in July 2006 with corrections to the Cover Date.