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。     

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.     

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.     

Confined Ni-In intermetallic alloy nanocatalyst with excellent coking resistance for methane dry reforming

Carbon dioxide and methane are two main greenhouse gases which are contributed to serious global warming.Fortunately,dry reforming of methane(DRM),a very important reaction developed decades ago,can convert these two major greenhouse gases into value-added syngas or hydrogen.The main problem retarding its industrialization is the seriously coking formation upon the nickel-based catalysts.Herein,a series of confined indium-nickel(In-Ni)intermetallic alloy nanocatalysts(In_xNi@SiO₂)have been prepared and displayed superior coking resistance for DRM reaction.The sample containing 0.5 wt.%of In loading(In_0.5Ni@SiO₂)shows the best balance of carbon deposition resistance and DRM reactivity even after 430 h long term stability test.The boosted carbon resistance can be ascribed to the confinement of core–shell structure and to the transfer of electrons from Indium to Nickel in In-Ni intermetallic alloys due to the smaller electronegativity of In.Both the silica shell and the increase of electron cloud density on metallic Ni can weaken the ability of Ni to activate C–H bond and decrease the deep cracking process of methane.The reaction over the confined InNi intermetallic alloy nanocatalyst was conformed to the Langmuir-Hinshelwood(L-H)mechanism revealed by in situ diffuse reflectance infrared Fourier transform spectroscopy(in-situ DRIFTS).This work provides a guidance to design high performance coking resistance catalysts for methane dry reforming to efficiently utilize these two main greenhouse gases.     

MOFs基材料在光催化CO2还原中的应用

系统总结了金属有机框架(MOFs)基材料在光催化还原CO₂中的最新研究进展, 其中包括MOFs直接作为光催化剂和作为复合光催化2个主要部分, 讨论了MOFs基光催化剂在催化还原CO₂方面展现出的独特优势, 并对MOFs基光催化剂的结构稳定性与CO₂转化效率等问题进行讨论与分析, 对未来发展趋势进行了展望.     

光催化CO_2转化为碳氢燃料体系的综述

传统化石能源燃烧产生CO2引起的地球变暖和能源短缺已经成为一个严重的全球性问题.利用太阳光和光催化材料将CO2还原为碳氢燃料,不仅可以减少空气中CO2浓度,降低温室效应的影响,还可以提供碳氢燃料,缓解能源短缺问题,因此日益受到各国科学家的高度关注.本文综述了光催化还原CO2为碳氢燃料的研究进展,介绍了光催化还原CO2的反应机理,并对现阶段报道的光催化还原CO2材料体系进行了整理和分类,包括TiO2光催化材料,ABO3型钙钛矿光催化材料,尖晶石型光催化材料,掺杂型光催化材料,复合光催化材料,V、W、Ge、Ga基光催化材料及石墨烯基光催化材料.评述了各种材料体系的特点及光催化性能的一些影响因素.最后对光催化还原CO2的研究前景进行了展望.     

光电催化二氧化碳还原研究进展

CO_2是最常见的化合物,作为潜在的碳一资源,可用于制备多种高附加值的化学品,如一氧化碳、甲烷、甲醇、甲酸等。传统的热催化转化CO_2方法能耗高,反应条件苛刻。因此,如何在温和条件下高效地将CO_2转化成高附加值的化学品,一直以来是催化领域的研究热点和难点之一。光催化技术反应条件温和、绿色环保。然而,纯光催化反应普遍存在太阳能利用效率有限,光生载流子分离效率低等问题。针对上述问题,在光催化的基础上引入电催化,可以提高载流子的分离效率,在较低的过电位下,实现多电子、质子向CO_2转移,从而提高催化反应效率。总之,光电催化技术可以结合光催化和电催化的优势,提高CO_2催化还原反应效率,为清洁、绿色利用CO_2提供了一种新方法。本文依据光电催化CO_2还原反应基本过程,从光吸收、载流子分离和界面反应等三个角度综述了光电催化反应的基本强化策略,并对未来可能的研究方向进行了展望。     

光催化CO2还原的超薄层状催化剂

The acceleration of industrialization and the continuous upgradation of consumption structure has increased the atmospheric content of CO₂ far beyond the past levels, leading to a serious global environmental problem. Photocatalytic reduction of CO₂ is one of the most promising methods to solve the problem of rising atmospheric CO₂ content. The core of this technology is to develop efficient, environment-friendly, and affordable photocatalysts. A photocatalyst is a semiconductor that can absorb photons from sunlight and produce electron-hole pairs to initiate a redox reaction. Owing to their low specific surface areas, significant electron-hole recombination, and less surface-active sites, bulk photocatalysts are not satisfactory. Ultrathin layered materials have shown great potential for photocatalytic CO₂ reduction owing to their characteristics of large specific surface area, a large number of low-coordination surface atoms, short transfer distance from the inside to the catalyst surface, along with other advantages. Photoexcited electrons only need to cover a short distance to transfer to the nanowafer surface, and the speed of migrating electrons on the nanowafer surface is much higher than that in the layers or in the bulk catalyst. The ultrathin structure leads to significant coordinative unsaturation and even vacancy defects in the lattice structure of the atoms; while the former can be used as active sites for CO₂ adsorption and reaction, the latter can improve the separation of the electron-hole pair. This review summarizes the latest developments in ultrathin layered photocatalysts for CO₂ reduction. First, the photocatalytic reduction mechanism of CO₂ is introduced briefly, and the factors governing product selectivity are explained. Second, the existing catalysts, such as g-C₃N₄, black phosphorus (BP), graphene oxide (GO), metal oxide, transition metal dichalcogenides (TMDCs), perovskite, BiOX (X = Cl, Br, I), layered double hydroxide (LDH), 2D-MOF, MXene, and two-dimensional honeycomb-like Ge―Si alloy compounds (gersiloxenes), are classified. In addition, the prevalent preparation methods are summarized, including mechanical stripping, gas stripping, liquid stripping, chemical etching, chemical vapor deposition (CVD), template method, self-assembly of surfactant, and the intermediate precursor method of lamellar Bi-oleate complex. Finally, we introduced the strategy of improving photocatalyst performance on the premise of maintaining its layered structure, including the factors of thickness adjustment, doping, structural defects, composite, etc. The future opportunities and challenges of ultrathin layered photocatalysts for the reduction of carbon dioxide have also been proposed.     

可见光驱动丰产金属卟啉类配合物催化的二氧化碳选择性还原反应

随着能源短缺和环境问题日益突出, 寻找清洁和可再生能源来替代化石燃料是本世纪科学家面临的最紧迫的任务之一. 为了实现我国“双碳”战略目标, 利用太阳能将二氧化碳(CO₂)转化为清洁燃料和化学品是实现社会可持续发展的途径之一. 催化剂是CO₂光还原技术的核心组成部分, 其可以吸附气态CO₂分子, 在可见光照射下将CO₂还原为一氧化碳(CO)、 甲酸(HCOOH)、 甲醇(CH₃OH)或甲烷(CH₄)等能源小分子. 目前, 新型CO₂还原光催化体系的开发取得了很好的进展. 本文综合评述了近年来均相及非均相丰产金属卟啉类催化剂在光催化CO₂还原中的研究进展, 并对在金属卟啉均相催化剂作用下, CO₂光还原为CO或CH₄的反应机理分别进行了介绍, 还讨论了金属卟啉基多孔有机聚合物与卟啉有机金属框架在光催化CO₂方面的重要应用. 最后, 对可见光驱动卟啉类金属配合物催化的CO₂还原的发展前景进行了展望.     

金属-有机框架基材料在二氧化碳光催化转化中的应用

将大气中的二氧化碳(CO₂)转化为燃料或高附加值化学品是降低大气中CO₂含量、 减缓温室效应的有效途径之一. 光催化CO₂化学转化条件温和, 能耗低, 在CO₂转化中占有重要地位. 金属-有机框架(MOF)基材料由于具有比表面积大、 光电性质优良和可调节性强等特点, 是CO₂光催化转化的常用催化剂之一. 本文综合评述了近两年MOF基材料在光催化CO₂还原反应、 CO₂环加成反应和CO₂羧基化反应中的应用, 阐释了MOF基材料在CO₂光催化转化中的优势和局限性, 并展望了其未来发展.     

二维/一维BiOBr0.5Cl0.5/WO3 S型异质结助力光催化CO2还原

S型异质结不但可以提高载流子的分离效率,还可以维持较强的氧化还原能力。因此,构建S型异质是提高光催化二氧化碳还原反应的有效途径。本研究通过静电自组装法构建了具有近红外光响应(> 780 nm)的二维BiOBr_0.5Cl_0.5纳米片和一维WO₃纳米棒S型异质结光催化剂,并用于高效还原二氧化碳。能带位置和界面电子相互作用的综合分析表明：在光催化二氧化碳还原反应过程中,BiOBr_0.5Cl_0.5/WO₃遵循S型电子转移路径;不仅提高了载流子的高效分离,还维持了两相(BiOBr_0.5Cl_0.5和WO₃)较高的氧化还原能力。此外,二维纳米片/一维纳米棒的结构使得半导体之间具备良好的界面接触,有利于载流子的分离,且暴露更多的活性位点,最终提高催化效率。结果显示,BiOBr_0.5Cl_0.5/WO₃异质结催化剂表现出较高的CO₂还原能力和CO选择性,CO的产率高达16.68 μmol∙g^-1∙h^-1,分别是BiOBr_0.5Cl_0.5的1.7倍和WO₃的9.8倍。本工作为构建S型二维/一维异质结光催化剂高效还原二氧化碳提供了新的思路。     

均相体系可见光催化还原CO2研究进展和面临挑战

利用太阳能将CO₂还原成可以利用的燃料或者有机物,是洁净新能源的重要研究方向,具有很大的挑战性。均相体系作为光催化还原CO₂最早研究的体系,对于CO₂还原的分子机理研究、新型催化剂设计以及体系优化方面具有重要指导意义。近五年来,均相体系光催化还原CO₂的研究取得了显著进展。本综述将对近五年来均相体系中光催化还原CO₂取得的重要研究进展进行综述,并对均相光催化体系发展面临的挑战进行了总结。     

纳米SiC基光催化剂研究进展

Industrialization undoubtedly boosts economic development and improves the standard of living; however, it also leads to some serious problems, including the energy crisis, environmental pollution, and global warming. These problems are associated with or caused by the high carbon dioxide (CO₂) and sulfur dioxide (SO₂) emissions from the burning of fossil fuels such as coal, oil, and gas. Photocatalysis is considered one of the most promising technologies for eliminating these problems because of the possibility of converting CO₂ into hydrocarbon fuels and other valuable chemicals using solar energy, hydrogen (H₂) production from water (H₂O) electrolysis, and degradation of pollutants. Among the various photocatalysts, silicon carbide (SiC) has great potential in the fields of photocatalysis, photoelectrocatalysis, and electrocatalysis because of its good electrical properties and photoelectrochemistry. This review is divided into six sections: introduction, fundamentals of nanostructured SiC, synthesis methods for obtaining nanostructured SiC photocatalysts, strategies for improving the activity of nanostructured SiC photocatalysts, applications of nanostructured SiC photocatalysts, and conclusions and prospects. The fundamentals of nanostructured SiC include its physicochemical characteristics. It possesses a range of unique physical properties, such as extreme hardness, high mechanical stability at high temperatures, a low thermal expansion coefficient, wide bandgap, and superior thermal conductivity. It also possesses exceptional chemical characteristics, such as high oxidation and corrosion resistance. The synthesis methods for obtaining nanostructured SiC have been systematically summarized as follows: Template growth, sol-gel, organic precursor pyrolysis, solvothermal synthesis, arc discharge, carbon thermal reduction, and electrospinning. These synthesis methods require high temperatures, and the reaction mechanism involves SiC formation via the reaction between carbon and silicon oxide. In the section of the review involving the strategies for improving the activity of nanostructured SiC photocatalysts, seven strategies are discussed, viz., element doping, construction of Z-scheme (or S-scheme) systems, supported co-catalysts, visible photosensitization, construction of semiconductor heterojunctions, supported carbon materials, and construction of nanostructures. All of these strategies, except element doping and visible photosensitization, concentrate on enhancing the separation of holes and electrons, while suppressing their recombination, thus improving the photocatalytic performance of the nanostructured SiC photocatalysts. Regarding the element doping and visible photosensitization strategies, element doping can narrow the bandgap of SiC, which generates more holes and electrons to improve photocatalytic activity. On the other hand, the principle of visible photosensitization is that photo-induced electrons move from photosensitizers to the conduction band of SiC to participate in the reaction, thus enhancing the photocatalytic performance. In the section on the applications of nanostructured SiC, photocatalytic H₂ production, pollutant degradation, CO₂ reduction, photoelectrocatalytic, and electrocatalytic applications will be discussed. The mechanism of a photocatalytic reaction requires the SiC photocatalyst to produce photo-induced electrons and holes during irradiation, which participate in the photocatalytic reaction. For example, photo-induced electrons can transform protons into H₂, as well as CO₂ into methane, methanol, or formic acid. Furthermore, photo-induced holes can convert organic waste into H₂O and CO₂. For photoelectrocatalytic and electrocatalytic applications, SiC is used as a catalyst under high temperatures and highly acidic or basic environments because of its remarkable physicochemical characteristics, including low thermal expansion, superior thermal conductivity, and high oxidation and corrosion resistance. The last section of the review will reveal the major obstacles impeding the industrial application of nanostructured SiC photocatalysts, such as insufficient visible absorption, slow reaction kinetics, and hard fabrication, as well as provide some ideas on how to overcome these obstacles.      

纳米SiC基光催化剂研究进展

工业化无疑促进了经济的发展,提高了生活水平,但也导致了一些问题,包括能源危机、环境污染、全球变暖等, 其中这些所产生问题主要是由燃烧煤炭、石油和天然气等化石燃料引起的。光催化技术具有利用太阳能将二氧化碳转化为碳氢化合物燃料、从水中制氢、降解污染物等优点,从而在解决能源危机的同时避免环境污染,因此被认为是解决这些问题的最有潜力的技术之一。在各种光催化剂中,碳化硅(SiC)由于其优良的电学性能和光电化学性质,在光催化、光电催化、电催化等领域具有广阔的应用前景。本文首先系统地阐述了各种SiC的合成方法,具体包括模板生长法、溶胶凝胶法、有机前驱物热解法、溶剂热合成法、电弧放电法,碳热还原法和静电纺丝等方法。然后详细地总结了提升SiC光催化活性的各种改性策略,如元素掺杂、构建Z型(S型)体系、负载助催化剂、可见光敏化、构建半导体异质结、负载炭材料、构建纳米结构等。最后重点论述了半导体的光催化机理以及SiC复合物在光催化产氢、污染物降解和CO₂还原等领域的应用研究进展,并提出了前景展望。