Synergistic assembly of dendrimer-templated platinum catalysts on nitrogen-doped carbon nanotube electrodes for oxygen reduction

A study of the synergistic tuning of nitrogen-doped carbon nanotubes (NCNTs) as support- and size-monodisperse platinum nanoparticles templated from G4-NH2 dendrimers (Pt-DEN's) as catalysts targeted toward oxygen reduction is reported. UV-vis spectroscopy, adsorption isotherms, TGA, TEM, and voltammetry were used to characterize the loading and activity of Pt-DENs immobilized on CNT and NCNT supports. The facile uptake of Pt-DENs was found to be influenced by the number of edge plane sites on the NCNT support with higher adsorption rates observed for NCNTs with increased nitrogen content. Pt-DEN/NCNT composites exhibit high activity with a mass-transport-limited current density and mass activity of 2.3 mA cm(-2) and 0.05 mA g(-1), respectively, for the oxygen reduction reaction (ORR).     

高分散在氮掺杂碳纳米管表面铂纳米粒子的高效甲醇电氧化性能

以氮掺杂碳纳米管（NCNT）为载体,利用掺杂氮原子的锚定作用,通过微波辅助乙二醇还原法方便地将Pt纳米粒子高分散地固载于NCNT表面,制得了Pt/NCNT系列催化剂,对催化剂制备规律、电催化甲醇氧化反应（MOR）性能及构效关系开展了系统深入的研究。结果表明,随Pt负载量在18.2%~58.7%（w/w,下同）范围增加,Pt纳米粒子的粒径在2.2~3.7 nm范围相应地逐渐增大。单位质量催化剂的MOR催化活性先增加后急剧减小,在负载量为47.8%时达到最大。Pt的质量比活性在中等负载量（27.6%~47.8%）区间出现高值平台。该变化规律源于Pt纳米粒子的MOR催化活性在3 nm前后的明显差异,即<3 nm时活性差,>3 nm时活性优异。高负载量（58.7%）时活性的急剧下降源于Pt纳米粒子因团聚引起的Pt利用率的降低。     

高分散在氮掺杂碳纳米管表面铂纳米粒子的高效甲醇电氧化性能

以氮掺杂碳纳米管(NCNT)为载体,利用掺杂氮原子的锚定作用,通过微波辅助乙二醇还原法方便地将Pt纳米粒子高分散地固载于NCNT表面,制得了Pt/NCNT系列催化剂,对催化剂制备规律、电催化甲醇氧化反应(MOR)性能及构效关系开展了系统深入的研究。结果表明,随Pt负载量在18.2%~58.7%(w/w,下同)范围增加,Pt纳米粒子的粒径在2.2~3.7 nm范围相应地逐渐增大。单位质量催化剂的MOR催化活性先增加后急剧减小,在负载量为47.8%时达到最大。Pt的质量比活性在中等负载量(27.6%~47.8%)区间出现高值平台。该变化规律源于Pt纳米粒子的MOR催化活性在3 nm前后的明显差异,即3 nm时活性差,3 nm时活性优异。高负载量(58.7%)时活性的急剧下降源于Pt纳米粒子因团聚引起的Pt利用率的降低。     

Highly Oriented Nitrogen-doped Carbon Nanotube Integrated Bimetallic Cobalt Copper Organic Framework for Non-enzymatic Electrochemical Glucose and Hydrogen Peroxide Sensor

The hierarchical three-dimensional nitrogen-doped carbon nanotube anchored bimetallic cobalt copper organic framework (NCNT MOF CoCu) is successfully synthesized by the direct growth approach using the high-temperature carbonization of bimetallic cobalt copper organic framework (MOF CoCu-500). The as-prepared NCNT MOF CoCu nanostructure possesses high-level activity for both glucose and hydrogen peroxide (H₂O₂) sensing molecules. The cyclic voltammetry (CV) and chronoamperometry (CA) studies demonstrate excellent electrocatalytic performance for the oxidation of glucose with a linear range of 0.05 to 2.5 mM, high sensitivity of 1027 μA mM⁻¹cm⁻², and the lowest detection limit of 0.15 μM. Similarly, the NCNT MOF CoCu nanostructure showed significantly higher H₂O₂ activity with a linear range of 0.05 to 3.5 mM, high sensitivity of 639.5 μA mM⁻¹cm⁻², and the lowest detection limit of 0.206 μM. Thanks to its special hierarchical nanoarchitecture, homogeneous nitrogen-doped carbon nanotubes, and highly graphitized carbon, which may be increased the synergistic effect between bimetallic CoCu and NCNT in the organic framework. The potentially effective fabricated sensor was also used as a suitable probe for the detection of glucose and H₂O₂ in the analysis of the real samples.     

Modulating the Charge-Transfer Step of a p–n Heterojunction with Nitrogen-Doped Carbon: A Promising Strategy To Improve Photocatalytic Performance

Engineering p–n heterojunctions among metal oxide semiconductors to provide a built-in electric field is an efficient strategy to facilitate the separation of photogenerated electrons and holes and improve their photocatalytic activities. However, the inherent poor conductivity of p–n heterojunctions still limits the charge-transfer step and thus hampers their practical application in photocatalysis. In this work, a nitrogen-doped carbon-coated NiO/TiO₂ p–n (NCNT) heterojunction with hierarchical mesoporous sphere morphology was synthesized by in situ pyrolytic decomposition of nickel–titanium complexes. The NiO/TiO₂ p–n heterojunction in NCNT was fully characterized by several techniques, supported by theoretical calculations and Mott–Schottky plots. On coating with a thin nitrogen-doped carbon layer, the electron transfer of the obtained p–n heterojunction could be significantly enhanced. On account of the favorable structural features of the p–n heterojunction with nitrogen-doped carbon coating and hierarchical mesoporous structure, NCNT exhibited excellent photocatalytic activity toward various reaction systems, including the hydrogen evolution reaction and the visible-light-induced hydroxylation of phenylboronic acids.     

Highly active Co-doped LaMnO3 perovskite oxide and N-doped carbon nanotube hybrid bi-functional catalyst for rechargeable zinc–air batteries

Herein, non-precious cobalt doped lanthanum manganese perovskite oxide nanoparticles are used as a growth substrate for nitrogen-doped carbon nanotubes to form efficient and durable hybrid bi-functional catalyst (LMCO/NCNT). LMCO/NCNT demonstrates significantly enhanced onset and half-wave oxygen reduction reaction (ORR) potentials (− 0.11 and − 0.24 V vs. SCE, respectively), and oxygen evolution reaction (OER) current density (27 mA cm^− 2 at 0.9 V vs. SCE). Likewise, practical rechargeable zinc–air battery testing using atmospheric air reveals superior discharge voltages obtained with LMCO/NCNT, particularly at current densities higher than 30 mA cm^− 2, and significantly lower charge voltages at all current densities tested, compared to state-of-art commercial platinum on carbon catalyst. In addition, very stable charge and discharge voltages of 2.2 and 1.0 V, respectively, are obtained over 60 cycles. The excellent performance and durability of the hybrid catalyst are attributed to very uniformly distributed LMCO nanoparticles on the surface of NCNT resulting in enhanced surface area and material utilization.     

Integrating NiCo Alloys with Their Oxides as Efficient Bifunctional Cathode Catalysts for Rechargeable Zinc–Air Batteries

The lack of high‐efficient, low‐cost, and durable bifunctional electrocatalysts that act simultaneously for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is currently one of the major obstacles to commercializing the electrical rechargeability of zinc–air batteries. A nanocomposite CoO‐NiO‐NiCo bifunctional electrocatalyst supported by nitrogen‐doped multiwall carbon nanotubes (NCNT/CoO‐NiO‐NiCo) exhibits excellent activity and stability for the ORR/OER in alkaline media. More importantly, real air cathodes made from the bifunctional NCNT/CoO‐NiO‐NiCo catalysts further demonstrated superior performance to state‐of‐the‐art Pt/C or Pt/C+IrO₂ catalysts in primary and rechargeable zinc–air batteries.     

High reaction activity of nitrogen-doped carbon nanotubes toward the electrooxidation of nitric oxide

Carbon nanotubes doped with N (NCNTs) enable 1.5 times faster electron-transfer kinetics for the oxidation of NO compared to pristine carbon nanotubes (CNTs), which may be due to the low adsorption energy for a NO on pyridinic NCNT(5,5) allowing NO to lose electrons readily and facilitate the following oxidation to nitrate.     

Synthesis of the nitrogen-doped carbon nanotube (NCNT) bouquets and their electrochemical properties

The nitrogen-doped carbon nanotube (NCNT) bouquets have been synthesized by the pyrolysis of nitrogen-containing ion-exchange resin. The material shows excellent oxygen reduction performance after being supported by the Pt nanoparticles (Pt/NCNTs) compared with commercial Pt/C (46.7 wt.% Pt, TKK, Japan) in terms of the onset potential, half-wave potential, mass activity and durability. The better ORR performance of the Pt/NCNTs indicates potential applications in PEMCs.     

The Role of Nitrogen-doping in the Catalytic Transfer Hydrogenation of Phenol to Cyclohexanone with Formic Acid over Pd supported on Carbon Nanotubes

Highly selective one-step hydrogenation of phenol to cyclohexanone, an important intermediate in the production of nylon 6 and nylon 66, is desirable but remains a challenge. Pd nanoparticles supported on nitrogen- and oxygen-functionalized carbon nanotubes (NCNTs, OCNTs) were prepared, characterized, and applied in the hydrogenation of phenol to cyclohexanone to study the effect of N-doping. Almost full conversion of phenol with high selectivity to cyclohexanone was achieved over Pd/NCNT under mild reaction conditions using either H₂ or formic acid (FA) as a hydrogen source. The effects of reaction temperature and FA/phenol ratio and the reusability were investigated. Separate FA decomposition experiments without and with the addition of phenol were performed to investigate the reaction mechanism, especially the deactivation behavior. Deactivation was observed for both catalysts during the FA decomposition, while only Pd/OCNT rather than Pd/NCNT was deactivated in the transfer hydrogenation with FA and the FA decomposition in the presence of phenol, indicating the unique role of N-doping. Therefore, we assume that deactivation is caused by the strongly bound formates on the active Pd sites, suppressing further FA decomposition and/or transfer hydrogenation on Pd. The nonplanar adsorption of phenol on NCNTs via weak O−H⋅⋅⋅N interactions enables the occurrence of the subsequent hydrogenation by adsorbed formate on Pd.     

A reevaluation of the correlation between the synthesis parameters and structure and properties of nitrogen-doped carbon nanotubes

Nitrogen-doped carbon nanotubes(NCNTs) were synthesized by chemical vapor deposition using cobaltbased oxides as catalyst and ethylenediamine(EDA) as carbon/nitrogen precursor. The influence of growth time,EDA concentration and growth temperature on the morphology,yield,composition,graphitization and oxidation resistance of the NCNTs was systematically investigated by using Raman spectroscopy,temperature-programmed oxidation and other techniques. The NCNT growth from ethylenediamine with a high N/C ratio involves several processes including mainly(1) catalytic growth of NCNTs,(2) homogeneous gas-phase decomposition of EDA,(3) non-catalytic deposition of pyrolytic carbon/nitrogen species and(4)surface etching of amorphous carbon or carbon at defect sites through gasification. At a later growth stage the etching process appears to be dominating,leading to the thinning of nanotubes and the decrease of yield.Moreover,the surface etching through carbon gasification strongly influences the structure and degree of graphitization of NCNTs.     

Iron atom–nanoparticles for interactional enhancing the electrocatalytic reaction activity in Li-S batteries

The undesirable shuttle effect and sluggish redox kinetics of polysulfides seriously result in low sulfur utilization and poor capacity retention. Here, an integrated strategy is proposed by rational designing multifunctional architecture to manipulate the redox kinetics of polysulfides, specifically, by employing iron atoms (Fe-As) and iron-species nanoparticles (Fe-NPs) co-embedded nitrogen-doped carbon nanotube (Fe-NCNT) as catalyst and host for sulfur. The synergistic cooperation of Fe-As and Fe-NPs provides efficient active sites to facilitate the diffusion, strengthen the affinities, and promote the conversion reactions for polysulfides. Furthermore, the NCNT not only offers practical Li⁺ transport pathways but also immobilize the polysulfides effectively. Benefiting from these merits, the Fe-NCNT/S electrodes exhibit high initial specific capacity of 1502.6 mAh/g at 0.1 C, outstanding rate performance (830 mAh/g at 2 C), and good cycling performance (597.8 mAh/g after 500 cycles with an ultralow capacity fading rate of 0.069% per cycle). This work features the distinct interaction of iron atom-nanoparticles on facilitating immobilization-diffusion-transformation process of polysulfides, and it also expected to pave the way for the application in practical Li-S batteries.     

Using ONIOM calculations to investigate the abilities of simple and nitrogen,boron, sulfur-doped carbon nanotubes in sensing of carbon monoxide

In this work, geometries, stabilities, and electronic properties of the carbon monoxide (CO) molecule as an adsorbent in a simple carbon nanotube (CNT) and nitrogen (N), boron (B), sulfur (S)-doped CNTs (NCNT, BCNT, and SCNT) with parallel and perpendicular configurations are fully considered using ONIOM, natural bond orbital, and quantum theory of atom in molecule (QTAIM) calculations. The adsorption energies (E_ad) demonstrate that a CO molecule could be adsorbed on the surface of the simple CNT with parallel configuration and N-doped CNT with perpendicular configuration in an exothermic process. QTAIM calculations showed the close-shell (noncovalent) interactions between the CO molecule and CNT or N, B, S-doped CNTs. In addition, the energy gap (E_g) values between the highest occupied molecular orbital and the lowest unoccupied molecular orbital are calculated. In accordance with the results of energy gap, simple and N-doped CNTs could be used as CO sensors.     

Highly graphitized carbon-wrapped PtFeCo alloy with enhanced durability and activity toward methanol electro-oxidation

Exploring efficient strategies to construct durable and active Pt-based electrocatalysts toward methanol oxidation reaction (MOR) remains great significance for the application of direct methanol fuel cells (DMFCs). Here, we report a facile pyrolysis procedure for fabricating carbon layer wrapped PtFeCo alloy nanoparticles supported on nitrogen-doped carbon nanotubes (NCNT). Physical characterizations demonstrate that the nitrogen-doped carbon support is highly graphitized and the PtFeCo particles are firmly wrapped by the graphitized carbon. Since the wrapping of highly graphitized carbon effectively prevents PtFeCo alloy from metal dissolution, the durability of the synthesized PtFeCo/Co–NCNT_a catalyst has been substantially improved, remaining about 76% of its initial mass activity after 1000 cycles of durability test in acid condition. In addition, due to the strain and ligand effects caused by alloying Pt with Fe and Co, the PtFeCo/Co–NCNT_a catalyst exhibits a greatly enhanced mass activity of 4.2-fold and a specific activity of 6.3-fold higher than those of commercial Pt/C-JM catalyst. Consequently, this work may provide an effective route for preparing durable and active Pt-based catalysts for methanol electro-oxidation.     

Bromine-Enhanced Generation and Epoxidation of Ethylene in Tandem CO2 Electrolysis Towards Ethylene Oxide

The indirect electro-epoxidation of ethylene (C₂H₄), produced from CO₂ electroreduction (CO₂R), holds immense promise for CO₂ upcycling to valuable ethylene oxide (EO). However, this process currently has a mediocre Faradaic efficiency (FE) due to sluggish formation and rapid dissociation of active species, as well as reductive deactivation of Cu-based electrocatalysts during the conversion of C₂H₄ to EO and CO₂ to C₂H₄, respectively. Herein, we report a bromine-induced dual-enhancement strategy designed to concurrently promote both C₂H₄-to-EO and CO₂-to-C₂H₄ conversions, thereby improving EO generation, using single-atom Pt on N-doped CNTs (Pt₁/NCNT) and Br⁻-bearing porous Cu₂O as anode and cathode electrocatalysts, respectively. Physicochemical characterizations including synchrotron X-ray absorption, operando infrared spectroscopy, and quasi in situ Raman spectroscopy/electron paramagnetic resonance with theoretical calculations reveal that the favorable Br₂/HBrO generation over Pt₁/NCNT with optimal intermediate binding facilitates C₂H₄-to-EO conversion with a high FE of 92.2 %, and concomitantly, the Br⁻ with strong nucleophilicity protects active Cu⁺ species in Cu₂O effectively for improved CO₂-to-C₂H₄ conversion with a FE of 66.9 % at 800 mA cm⁻², superior to those in the traditional chloride-mediated case. Consequently, a single-pass FE as high as 41.1 % for CO₂-to-EO conversion can be achieved in a tandem system.     

聚苯胺改性氮掺杂碳纳米管制备及其超级电容器性能

利用苯胺原位化学聚合合成聚苯胺包覆碳纳米管(CNTs), 再炭化处理制备氮掺杂碳纳米管(NCNTs).激光拉曼(Raman)光谱和X射线光电子谱(XPS)分析及透射电镜(TEM)观察表明, 苯胺包覆碳纳米管经炭化处理后, 得到以碳纳米管为核、氮掺杂碳层为壳, 具有核-壳结构的氮掺杂碳纳米管, 而碳纳米管本征结构未遭破坏. 研究表明, 随着苯胺用量的增大, 氮掺杂碳纳米管的氮掺杂碳层变厚, 氮含量从7.06%(质量分数)增加到8.64%, 而作为超级电容器电极材料, 随着氮掺杂碳层厚度降低, 氮掺杂碳纳米管在6 mol·L^-1氢氧化钾电解液中的比容量从107 F·g^-1增大到205 F·g^-1, 远高于原始碳纳米管10 F·g^-1的比容量, 且聚苯胺改性氮掺杂碳纳米管表现出较好的充放电循环性, 经1000次充放电循环后仍保持初始容量的92.8%~97.1%, 表明氮掺杂碳纳米管不仅通过表面氮杂原子引入大的法拉第电容和改善亲水性使电容量显著增大, 其具有的核壳结构特征也使循环稳定性增强。     

熔融制样-X射线荧光测定钨钼锡矿中的主次成分

采用熔融制样-X射线荧光光谱法测定矿物中的Cu、Pb、Zn、Mo、W、Al、Fe、Si、K、Na、Ti、Ca、Sn等13种主次量元素,采用混合均匀的三混熔剂,以硝酸锂为氧化剂、溴化锂为脱膜剂,进行实验条件优化选择。在650℃下对样品进行预氧化,在1100℃下高温熔融,熔融时间为300 s,最后制成均匀透明,表面光滑无气孔的熔片,以部分国家一级标准物质和自制的钨钼锡标准样品,熔融制片进行测定,线性拟合建立标准曲线,并通过测定谱线选择、基体校正,使钨钼锡的测定范围扩宽,从微量到主量均能进行测定,并且适用于多种不同矿石的测定。样品的组成和含量变化会对分析线强度造成吸收、增强以及谱线重叠的影响,采用经验系数和理论α系数结合来校正其产生的基体效应。相同条件下熔融10个标准样品进行测定,其相对标准偏差(RSD)均小于5%,表明方法的准确度、精密度均满足国家相关质量标准的要求。选用一些含量不同的标准样品进行测定,最终的测定结果与标准值相符,表明方法可用于钨钼锡矿的测定。     

128例脑性瘫痪血钙、锌、铁、铜、镁元素分析

为探讨小儿脑性瘫痪(CP)体内微量元素的变化,测定了128例脑性瘫痪患者血钙、锌、铁、铜、镁含量,随机选择128例正常儿童进行对照分析。结果表明,两组病例血锌、铜、镁均在正常范围,脑瘫组血钙56例、铁45例低于正常参考值,健康组血钙16例、铁11例低于正常参考值。经统计学处理,两组病例中血钙、铁、铜、镁含量具有显著性差异(P<0.05),血锌无显著性差异(P>0.05)。提示脑瘫儿童血钙、铁、铜、镁含量均低于正常儿童,补充钙、铁、镁等可能有利于脑瘫康复。     

中药质量控制技术发展展望

本文从中药产业需求、现代化需求、技术需求、机遇与挑战等方面概括了中药质量控制技术发展的背景;讨论了中药质量控制技术对于提高中药药效和安全性、推动产业发展和推进中药国际化的意义;综述了中药质量控制技术的现状,分析了在过程控制、安全性控制、标准品和对照品制备、指纹图谱技术等方面的不足;提出了中药质量控制技术应重点发展以分离和表征技术为主的中药质量控制关键技术、中药安全性控制技术、中药质量控制标准体系、中药质量控制原创性技术和中药标准品、对照品生产技术,制定技术标准,建立具有中药特色的过程控制和产品质量控制标准。     

血清铁、锌、钙、镁、磷与妊娠的关系探讨

为探讨血清铁、锌、钙、镁、磷在孕妇体内的水平，做好围产期孕妇的保健工作，提高孕产妇的健康水平和新生儿健康素质，抽取125例孕中期妇女空腹静脉血，采用透射比浊法测定了其血清铁、锌、钙、镁、磷的含量。结果表明，铁、锌、钙、镁、磷的异常在孕妇中有一定的发生率，其中尤以钙与锌的缺乏最为多见。提示应定期检测孕妇血清铁、锌、钙、镁、磷水平，并采取相府的防治措施．以提高孕产妇及新生儿的健康水平。