Paper-derived cobalt and nitrogen co-doped carbon nanotube@porous carbon as a nonprecious metal electrocatalyst for the oxygen reduction reaction

The oxygen reduction reaction (ORR) is a vitally important process in fuel cells. The development of high-performance and low-cost ORR electrocatalysts with outstanding stability is essential for the commercialization of the electrochemical energy technology. Herein, we report a facile synthesis of cobalt (Co) and nitrogen (N) co-doped carbon nanotube@porous carbon (Co/N/CNT@PC-800) electrocatalyst through a one-step pyrolysis of waste paper, dicyandiamide, and cobalt(II) acetylacetonate. The surface of the hierarchical porous carbon supported a large number of carbon nanotubes (CNTs), which were derived from dicyandiamide through the catalysis of Co. The addition of Co resulted in the formation of a hierarchical micro/mesoporous structure, which was beneficial for the exposure of active sites and rapid transportation of ORR-relevant species (O₂, H⁺, OH^?, and H₂O). The doped N and Co formed more active sites to enhance the ORR activity of the electrocatalyst. The Co/N/CNT@PC-800 material exhibited optimal ORR performance with an onset potential of 0.005 V vs. Ag/AgCl and a half-wave potential of –0.173 V vs. Ag/AgCl. Meanwhile, the electrocatalyst showed an excellent methanol tolerance and a long-term operational durability than that of Pt/C, as well as a quasi-four-electron reaction pathway. The low-cost and simple synthesis approach makes the Co/N/CNT@PC-800 a prospective electrocatalyst for the ORR. Furthermore, this work provides an alternative approach for exploring the use of biomass-derived electrocatalysts for renewable energy applications.     

氮掺杂碳纳米管负载的Ru和Pd催化剂上异丙醇的转化(英文)

Ru and Pd (2 wt%) loaded on pure and on Ndoped carbon nanotubes (NCNTs) were prepared and tested using the isopropyl alcohol decomposition reaction as probe reaction. The presence of nitrogen functionalities (pyridinic, pyrrolic, and quaternary nitrogen) on the nitrogen doped support induced a higher metal dispersion: Pd/NCNT (1.8 nm) Pd/CNT (4.9 nm), and Ru/NCNT (2.4 nm) Ru/CNT (3.0 nm). The catalytic activity of the supports was determined first. Isopropyl alcohol conversion produces acetone on CNTs while on NCNTs it led to both dehydration and dehydrogenation products. At 210 °C and in the presence of air, the isopropyl alcohol conversion was higher on the NCNTs (25%) than on the CNTs (11%). The Pd loaded catalysts were more active and more selective than the Ru ones. At 115 °C, the Pd catalysts were 100% selective towards acetone for a conversion of 100%, whereas the Ru catalysts led to dehydration and dehydrogenation products. The nitrogen doping induced the appearance of redox properties when oxygen is present in the reaction mixture.     

有机膦酸盐衍生的氮掺杂的磷酸钴/碳纳米管杂化材料作为高效氧还原电催化剂（英文）

随着环境污染和能源危机的日益严重,探索高效的非贵金属氧还原电催化剂来替代商业Pt/C迫在眉睫.其中,报道比较多的是具有钴基活性物种和氮掺杂碳的复合材料例如Co-Nx-C, Co3O4/GO, Co-N/CNT等,该复合材料具有高导电性、良好的稳定性和优异的催化活性.与其他钴基催化剂相比,磷酸钴由于其成本低廉,对环境友好,多功能的优良特性,已被广泛应用于催化、吸附、分离及储能等领域,在电催化方面也有极大的应用潜力.研究表明,磷酸基团不仅可以充当质子受体,也会诱导局部钴原子的几何结构发生扭曲,从而有利于水分子的吸附并促进析氧反应的发生.此外,磷酸钴也被证实具有一定的氧还原活性.尽管磷酸钴电催化剂的研究已经取得了一定进展,磷酸根有利于质子传输,但是其导电性很差,不利于电荷的转移和传输,使得其电催化活性不高.将磷酸钴和导电碳材料复合是解决问题的有效方法.而且,磷酸钴在碱性溶液中并不稳定,极大限制了其在电催化氧还原中的应用.金属有机膦酸盐是一类包含金属离子和有机膦酸配体的杂化材料,通过简单的焙烧便可以很容易地得到金属无机磷酸盐,并且在焙烧过程中氮掺杂的碳也会原位产生,并包覆在磷酸钴的表面,使得其导电性和催化活性大大提高.为此,本研究组制备了有机膦酸钴衍生的磷酸钴和氮磷掺杂的石墨烯的复合材料并用于电催化氧还原和析氧反应,所得到的材料导电性和稳定性良好,然而,该催化剂的表观活性与商业Pt/C相比仍有较大差距,且使用有机膦酸钴作为前驱体对活性的影响也不甚清楚.因此,本文采用含氮的有机膦酸配体乙二胺四亚甲基膦酸钠(EDTMPS)为磷源制备了氮掺杂的磷酸钴/碳纳米管杂化材料(CoPiC-N/CNT-3),其催化活性和稳定性良好,并进一步探讨了各种不同因素对电催化活性的影响.XRD和TEM结果表明,用这种方法得到的磷酸钴(CoPiC)为Co2P2O7物相,与磷酸二氢钠为磷源制备得到的CoPi相比,CoPiC的表面有石墨化碳层的存在, EDS图谱表明, Co, P, C, N均匀地掺杂到复合材料的骨架结构中.Raman光谱结果表明,石墨化碳层的存在和适量的碳纳米管的引入均可以增强复合材料的石墨化程度并提高了导电性,而氮掺杂导致其缺陷位点增多.XPS结果进一步表明,有机膦酸钴可以作为前驱体可制得氮掺杂的磷酸钴/碳纳米管杂化材料.电催化反应测试表明, CoPi C-N/CNT-3的氧还原活性与商业Pt/C相当,其遵循的是4电子的反应路径,而且抗甲醇氧化能力和稳定性均优于Pt/C.原因主要归结于以下几点:(1)磷酸钴颗粒与氧化碳纳米管的协同作用可以显著增强氧还原催化活性,引入的碳纳米管可以克服磷酸钴导电性差的缺陷;(2)磷酸钴在复合材料中分散均匀,使得可以充分利用催化剂的活性位点;(3)氮掺杂可以调变材料的电子结构,从而改善催化活性;(4)石墨化碳层的存在可以改善材料的电子导电性和稳定性,有利于电子转移并可以保护磷酸钴颗粒在催化氧还原反应过程中不被电解液腐蚀.可见,所制有机膦酸衍生的氮掺杂的磷酸钴/碳纳米管杂化材料有望替代Pt/C催化剂,并推动清洁可再生能源领域的相关研究.     

Comparing the deactivation behaviour of Co/CNT and Co/γ-Al2O3 nano catalysts in Fischer-Tropsch synthesis

An extensive study of Fischer-Tropsch (FT) synthesis on cobalt nano particles supported on γ-alumina and carbon nanotubes (CNTs) catalysts is reported.20 wt% of cobalt is loaded on the supports by impregnation method.The deactivation of the two catalysts was studied at 220 C,2 MPa and 2.7 L/h feed flow rate using a fixed bed micro-reactor.The calcined fresh and used catalysts were characterized extensively and different sources of catalyst deactivation were identified.Formation of cobalt-support mixed oxides in the form of xCoO yAl2O3 and cobalt aluminates formation were the main sources of the Co/γ-Al2O3 catalyst deactivation.However sintering and cluster growth of cobalt nano particles are the main sources of the Co/CNTs catalyst deactivation.In the case of the Co/γ-Al2O3 catalyst,after 720 h on stream of continuous FT synthesis the average cobalt nano particles diameter increased from 15.9 to 18.4 nm,whereas,under the same reaction conditions the average cobalt nano particles diameter of the Co/CNTs increased from 11.2 to 17.8 nm.Although,the initial FT activity of the Co/CNTs was 26% higher than that of the Co/γ-Al2O3,the FT activity over the Co/CNTs after 720 h on stream decreased by 49% and that over the Co/γ-Al2O3 by 32%.For the Co/γ-Al2O3 catalyst 6.7% of total activity loss and for the Co/CNTs catalyst 11.6% of total activity loss cannot be recovered after regeneration of the catalyst at the same conditions of the first regeneration step.It is concluded that using CNTs as cobalt catalyst support is beneficial in carbon utilization as compared to γ-Al2O3 support,but the Co/CNTs catalyst is more susceptible for deactivation.     

Electrodeposition of cobalt oxide films from carbonate solutions containing Co(II)–tartrate complexes

An electrochemical procedure of anodic deposition of cobalt oxyhydroxide film on a glassy carbon substrate in an alkaline medium (i.e. pH 11.6) is described. The electrodeposited film was obtained either by voltage cycling or by potentiostatic conditions using non-deaerated 0.1 M Na₂CO₃ solutions containing 40 mM tartrate ions and 4 mM CoCl₂. The effects on the film formation and growth, such as tartrate–cobalt ratio, pH, applied potential, etc. were widely evaluated. The electrodeposition process, under anodic conditions and moderately alkaline solutions, most likely involves a redox transition Co(II)→Co(III)/Co(IV) with destruction of the tartrate complex and formation of insoluble oxide/hydroxide cobalt species on the glassy carbon surface. The resulting cobalt oxyhydroxide films were characterised by cyclic voltammetry (CV) in 0.1 M NaOH solutions and by scanning electron microscopy (SEM) analysis after different strategies of preparation and various electrochemical treatments. The electrochemical activity of the deposited films was checked using various organic molecules as model compounds.     

N-CNTs/NiCo-LDH复合材料的制备及电化学性能

通过高温碳化聚吡咯纳米管制备了氮掺杂碳纳米管(N-CNTs), 并采用共沉淀法将镍钴层状双氢氧化物(NiCo-LDH)原位生长在N-CNTs上, 制备出具有三维互联网状结构的N-CNTs/NiCo-LDH复合材料. 研究了镍钴摩尔比对N-CNTs/NiCo-LDH复合材料形貌结构和电化学性能的影响. 结果表明, 当镍钴摩尔比为1∶2时, N-CNTs/Ni₁Co₂-LDH具有最佳的电化学性能. 在1 A/g电流密度下, 其比电容可达1311.8 F/g; 当电流密度为 10 A/g时, 电容保持率高达88.3%, 展现出优异的倍率性; 在经过2500次循环后, 电容保持率仍可达76.4%, 具有良好的循环稳定性.由N-CNTs/Ni₁Co₂-LDH与活性炭(AC)电极所构建的N-CNTs/Ni₁Co₂-LDH//AC水系混合型超级电容器, 在750 W/kg功率密度下, 具有27.19 W·h/kg的高能量密度.     

Effect of cobalt weight content on the structure and catalytic properties of Co/CNT catalysts in the fischer–tropsch synthesis

Cobalt-based Fischer–Tropsch synthesis (FTS) catalysts containing 1 to 40 wt % cobalt supported on multi-walled carbon nanotubes (CNTs) have been investigated. The CNTs have been characterized by low-temperature nitrogen adsorption, scanning electron microscopy, and X-ray photoelectron spectroscopy. All catalysts have been prepared by impregnating, with an ethanolic solution of cobalt nitrate, the CNTs preoxidized with concentrated nitric acid and have been tested in the FTS at 220°C and atmospheric pressure. Correlations have been established between the cobalt weight content of the catalyst and the Co particle size determined by transmission electron microscopy and X-ray diffraction. The Co content and particle size have an effect on the activity and selectivity of the catalyst and on the target fraction (C₅₊) yield in the FTS. The highest CO conversion is observed for the catalyst containing 20 wt % Co; the highest selectivity and activity, for the catalyst containing 5 wt % Co; the highest C₅₊ yield, for the catalyst containing 10 wt % Co.     

Enhanced electrocatalytic performance of functionalized carbon nanotube electrodes for oxygen reduction in proton exchange membrane fuel cells

Although nitrogen doped CNTs (N-CNTs) are considered as a promising alternative to platinized carbon for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs), the origin of the enhanced ORR activity with N-CNTs is not clear at present. Among several plausible reasons, the exposure of edge plane and creation of impurity band/surface states near the Fermi level are considered as major causes behind the catalytic activity. However, CNTs without nitrogen doping are not known to catalyze the ORR. In this work, we study the ORR activity of functionalized carbon nanotubes with different functional groups, such as sulfonic acid and phosphonic acid, in order to understand the role of surface functionalities in catalyzing the reaction. Functionalized CNTs show significantly enhanced activity towards the ORR, while CNTs without such surface functional groups do not reveal any such special ORR activity. Linear sweep voltammetry experiments with different rotation rates show diffusion controlled limiting current values for functionalized CNTs, and the 'n' values derived from Koutecky-Levich plots are 3.3 and 1.7 for S-MWCNTs and P-MWCNTs, respectively. This work demonstrates the ORR activity of functionalized MWCNTs, which opens up new strategies for electrocatalyst design in PEMFCs.     

钴掺杂对碳化钼催化噻吩加氢脱硫性能的影响

以MoO3和CoMo混合氧化物为前驱体, 制备了碳化钼和碳化钼-钴催化剂, 采用XRD, BET, SEM和XPS等技术对其进行了表征, 研究了Co掺杂对碳化钼催化剂噻吩加氢脱硫性能的影响. 结果表明, 掺入适量的Co后制得的CoMo双金属混合氧化物为MoO3和CoMoO4的两相混合体, 经CH4/H2气氛程序升温还原碳化反应生成共生共存的Co-Mo2C, Co以金属细颗粒的形态均匀地分散在生成的Mo2C组分之间. 在共生过程中含Co物种的掺入可降低制备碳化钼所需要的还原碳化温度, 使制备的碳化钼颗粒变小, 比表面积增大, 表面Mo2+含量增多, 从而对碳化钼的噻吩加氢脱硫活性有较好的促进作用, Co的添加量以Co/Mo摩尔比为0.2左右较为适宜. 用化学共沉淀法制得的Co-Mo2C共生共存体系的噻吩加氢脱硫反应活性, 好于由金属Co与Mo2C机械混合法制得的Co+Mo2C二相共存体系. 这表明当两个活性相共存时, 只有经过相互共生过程才能发挥其最佳的协同效应.     

E?ect of Thermal Treatment on Structure and Catalytic Activity of Supported Fischer-Tropsch Nano-Cobalt Catalysts for Clean Fuels

"A series of 15%Co/Al2O3 catalysts were prepared by incipient wetness impregnation under various calcination conditions (90-500 oC), and were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy experiments (XPS), temperature programmed reduction, and catalytic measurements of hydrogenation of carbon monoxide to long-chained hydrocarbons leading to clean fuels (Fischer-Tropsch synthesis). The results of XPS show the presence of incompletely decomposed cobalt nitrate for catalysts calcined at 90-200 oC, and the presence of Co3O4 for catalysts calcined at 200-500 oC. For the four alumina-supported nano cobalt catalysts with different thermal treatment (200-500 oC), XRD and XPS results illustrated that there were mainly nano Co3O4 crystalite phases of 9-10 nm and the size of cobalt nano-particles did almost not change with the different temperature of thermal treatment. This was different from that of silica-supported cobalt catalysts. The supported cobalt catalyst (CoAp340 sample) calcinated at 340 oC presented a better activity for Fischer Tropsch synthesis to clean fuels, at mild conditions like atmospheric pressure (100 kPa), 1800 mL/g/h and 190 oC; rather than high pressure (2 MPa or more)."     

Co-N4大环配合物分子应用于异相电催化CO2还原

利用可再生能源产生的电能催化二氧化碳还原(CO₂RR)是可持续制备碳基化学品的一种潜在途径.电催化剂是实现这个转化的关键,目前还需要深入地研究机理去优化催化剂的设计.M-N₄结构的大环配合物是一类结构明确、性能易调控的分子电催化剂,是研究结构-性能关系的理想平台.其中,金属酞菁在异相电催化CO₂RR中展现出较好的催化性能,受到广泛关注.而其它M-N₄结构大环配合物(如金属卟啉、金属咔咯)在异相电催化CO₂RR中报道较少,且催化性能一般.本文对比研究了酞菁钴(CoPc)、四苯基卟啉钴(CoTPP)和三苯基咔咯钴(CoTPC)三种分子异相电催化CO₂RR的性能,揭示制约金属卟啉和金属咔咯分子应用于异相体系的原因,并提出改进方法.首先采用碳纳米管(CNT)复合的方法对三种分子进行了研究.结果表明,只有CoPc能够与CNT形成性能优异的复合电催化剂,而CoTPP和CoTPC复合电催化剂几乎不具备活性.这是因为这两种分子具有扭曲的苯环导致分子与CNT作用力弱,在复合物里面只有很少的分子锚定在CNT上.本文采用直接滴涂法制备三种分子与CNT物理混合电极,并研究了分子载量对催化性能的影响.结果表明,在1.08×10^-8molcm^-2低分子载量时,CoTPP+CNT和Co TPC+CNT样品基本无活性,它们的电催化活性随着分子载量的提升而显著增加.在5.4×10^-7molcm^-2的高载量时,CoTPC+CNT和CoTPP+CNT样品在-0.67 V(相对可逆氢电极,下同)的电位下分别展现出14.0和7.61 mA cm^-2的CO分电流密度,是1.08×10^-8 molcm^-2载量样品的8.7和7.9倍.这说明对于Co TPP和CoTPC分子,可以通过加大载量来增加与CNT作用几率,从而提高电极活性.然而,基于CoPc制备的样品活性随着CoPc分子载量的增加变化不明显.这是由于在低载量下CoPc分子已经很好地与CNT相互作用,并且CNT上CoPc分子负载量是有限的,继续增大载量只会导致聚集.本文进一步发展一种聚乙烯吡啶(PVP)桥连的办法,提升CoTPP和CoTPC在低载量下的电极活性.聚乙烯链能够通过疏水作用缠绕在CNT上,同时吡啶能够与分子金属中心配位,从而为分子与CNT结合建立桥梁.当分子载量为1.08×10^-8mol cm^-2时,CoTPP+CNT/PVP在-0.67 V电位下展现出85%以上的CO法拉第效率,而且CO分电流密度达到7.84 mA cm^-2,是没有添加PVP对比样CoTPP+CNT的8倍.由此可见,分子与基底的相互作用强度对异相电催化CO₂RR的性能有重要影响.对于与基底相互作用弱的大环配合物分子可以通过大分子载量的滴涂法或引入桥连分子来提高电极性能.这些方法可以拓展到其它分子体系,有助于构建高效的异相分子电催化剂.     

Syntheses,Structures and Characterization of Cobalt(II) and Cobalt(III) Complexes with N-Benzylated Polyamines and a Terminal Azido Ligand

Mononuclear cobalt(II) and cobalt(III) complexes, [Co(trenb)(N₃)]Cl (1) and [Co(dienb)(N₃)₂(OAc)] (2) (trenb = tris[2-(benzylamino)ethyl]amine, dienb = 1,9-diphenyl-2,5,8-triazanonane) were synthesized and characterized by elemental analyses, IR and electronic spectra. Their crystal structures were also determined by X-ray diffraction analyses. In Complex 1, cobalt(II) is five-coordinate trigonal bipyramidal with one azido nitrogen atom and four nitrogen donors of the tripodal ligand; the chloride interacts weakly with one of the secondary amino groups of trenb via a hydrogen bond. In Complex 2, cobalt(III) is in a distorted octahedral coordination environment, consisting of three nitrogen atoms of the amine ligand, two azide nitrogen atoms and an oxygen atom of the acetate ion; a six-membered ring involving the hydrogen bond may stabilize the complex, which maintains its solid geometry in DMF as indicated by the electronic spectrum.     

Nitrogen-doped carbon nanotubes for heat transfer applications

In this research, it is aimed to enhance the heat transfer properties of the carbon nanotubes through nitrogen doping. To this end, nitrogen-doped multiwall carbon nanotubes (N-CNTs) were synthesized via chemical vapor deposition method. For supplying carbon and nitrogen during the synthesis of N-CNTs, camphor and urea were used, respectively, at 1000 °C over Co–Mo/MgO nanocatalyst in a hydrogen atmosphere. N-CNTs with three different nitrogen loadings of 0.56, 0.98, and 1.38 mass% were synthesized, after which, water/N-CNT nanofluids of these three samples with concentrations of 0.1, 0.2, and 0.5 mass% were prepared. To obtain a stable nanofluid, N-CNTs were functionalized by nitric acid followed by stabilizing in water by employing the ultrasonic bath. Investigation on the stability of the samples showed a high stability level for the prepared water/N-CNT nanofluids in which the zeta potential of ??43.5 mV was obtained for the best sample. Also for studying the heat transfer properties, the thermal conductivity in the range of 0.1–0.5 mass% and convection heat transfer coefficients of nanofluids in the range of 0.1–0.5 mass%, and Reynolds number in the range of 4000–9000 were evaluated. The results showed 32.7% enhancement of the convection heat transfer coefficients at Reynolds number of 8676 and 27% increase in the thermal conductivity at 0.5 mass% and 30 °C.

     

A novel cobalt hexacyanoferrate nanocomposite on CNT scaffold by seed medium and application for biosensor

In this paper, for the first time, we introduced the seed-mediated method to the growth of cobalt hexacyanoferrate nanoparticles (CoNPs), using 3.5 nm gold nanoparticles as seeds and multiwalled carbon nanotubes (MWCNTs) as growth scaffold which would both show synergistic action toward the reduction of H₂O₂. Via gold seeds, the one-step fabrication of CoNPs on the glassy carbon electrode is simple without any linking reagents, which will ingeniously exert the electrochemical properties of cobalt hexacyanoferrate. Combined with glucose oxidase, the sensing surface is applied as a biosensor for glucose. The growth of CoNPs is a chemical deposition process around the small Au nanoseed particles. The nanoseeds bridge the CoNPs and CNTs to form a smart nanocomposite. Spherical CoNPs have a relatively moderate dispersion on the three-dimensional network of CNTs with relatively even diameter ca. 100 nm. Whereas, in the control experiments without gold seeds cobalt hexacyanoferrate can only form continuous films, of which the size is far from nanolevel and the catalytic ability is poor. The synthesis and fabrication/modification of CoNPs are simple and fast without prior preparation of CoNPs and lengthy process of cross-linking. The amount of the seeds and CNTs, growth time and concentration of growth solution were investigated. Scanning electron microscopy (SEM) and electrochemical method were used.     

氮掺杂碳纳米管包覆碳化硅作为不含金属的催化剂(英文)

A hierarchical metal-free catalyst consisting of nitrogen-doped carbon nanotubes decorated onto a silicon carbide (N-CNTs/SiC) macroscopic host structure was prepared. The influence of N-CNTs incorporation on the physical properties of the support was evaluated using different characterization techniques. The catalyst was tested as a metal-free catalyst in the selective oxidation of H2S and steam-free dehydrogenation of ethylbenzene. The N-CNTs/SiC catalyst exhibited extremely good desulfurization performance compared to a Fe2O3/SiC catalyst under less conducive reaction conditions such as low temperature, high space velocity, and a low O2-to-H2S molar ratio. For the dehy-drogenation of ethylbenzene, a higher dehydrogenation activity was obtained with the N-CNTs/SiC catalyst compared to a commercial K-Fe/Al2O3 catalyst. The N-CNTs/SiC catalyst also displayed good stability as a function of time on stream for both reactions, which was attributed to the strong anchoring of the nitrogen dopant in the carbon matrix. The extrudate shape of the SiC support allowed the direct macroscopic shaping of the catalyst for use in a conventional fixed-bed reactor without the problems of catalyst handling, transportation, and pressure drop across the catalyst bed that are encountered with nanoscopic carbon-based catalysts.     

氧还原和析氧反应的双功能电催化剂--氮磷共掺碳负载四氧化三钴

金属-空气电池具备诸多优势,譬如绿色环保、能量转化率高、启动快速、能量密度高、使用寿命和干态存储时间长等.与燃料电池相比,金属-空气电池结构简单,放电电压平稳,成本低,但依然存在一些制约发展的问题,如阴极催化剂.阴极催化剂在金属-空气电池中发挥催化氧还原反应(oxygen reduction reaction, ORR)和析氧反应(oxygen evolution reac-tion, OER)的关键作用.铂及其合金常用作 ORR的单功能催化剂,而钌和铱等是目前 OER催化效率最高的,但 ORR活性很低,因此需要开发出一种廉价而又具备双功能催化作用的催化剂.单异原子掺杂的碳基催化剂的研究集中在 ORR催化性能上,而多异原子共掺碳最近有研究表明具有双催化氧的性质,如氮磷共掺碳.在这些氮磷共掺的碳架中,氮磷共掺物起着 OER催化作用,掺氮物为 ORR催化的活性位点,而掺磷物起着强化作用.异原子掺杂负载的钴基催化剂(如掺氮还原氧化石墨烯载 Co3O4)是近年来双功能催化剂研究的另一个热点.钴基催化剂有着催化 ORR和 OER的多价价态,然而其本身导电性能差,这一缺陷可通过杂化石墨化碳来弥补,石墨化碳有着优良的导电性能.据我们所知,目前仍没有关于氮磷共掺碳负载的 Co3O4双催化氧的研究.我们合成了氮磷共掺碳(NPC)负载的 Co3O4(Co3O4/NPC),并首次探索了其氧还原和析氧性能. Co3O4/NPC合成分两步进行.首先通过三聚氰胺与植酸之间的酯化或缩聚覆盖在导电炭黑颗粒表面,在保护气氛下焙烧得到 NPC,然后经溶剂热反应以及空气中氧化合成 Co3O4/NPC.催化剂的性能综合考虑了催化活性和稳定性两方面.采用线性扫描伏安法评估了 OER和 ORR的催化活性.对于 OER, Co3O4/NPC的起始电势是0.54 V (以饱和甘汞电极为参比电极),在0.80 V时电流密度达到21.95 mA/cm2,均优于 Co3O4/C和 NPC. Co3O4/NPC的高效 OER催化可归因于氮磷共掺物与 Co3O4之间的协同作用.对于 ORR, Co3O4/NPC的催化效率与商用 Pt/C相近,它们的扩散极限电流密度分别为–4.49和–4.76 mA/cm2(E =–0.80 V).在 ORR过程中, Co3O4起到主要的催化作用.采用计时电流(电流-时间)法评估了催化剂的稳定性.经6 h测定,对于 OER, Co3O4/NPC剩46%电流;而对于 ORR,剩95%电流.整体而言, Co3O4/NPC在 OER和 ORR中都表现出高的催化效率以及良好的稳定性.     

CVD synthesis of nitrogen doped carbon nanotubes using ferrocene/aniline mixtures

Nitrogen doped carbon nanotubes (N-CNTs) have been synthesized by the chemical vapour deposition (CVD) floating catalyst method using either 4-ferrocenylaniline or mixtures of varying concentrations of ferrocene/aniline together with toluene as added carbon source. The N-CNTs produced are less stable (thermal gravimetric analysis measurements), less graphitic and more disordered (transmission electron microscope measurements) than their undoped counterparts. The ratio of the Raman D- and G-band intensities increase with the nitrogen concentration used during the CNT growth. Furthermore, the transmission electron microscope (TEM) studies reveal that the CNTs are multi-walled (MW), and that the diameters of the N-MWCNTs can be controlled by systematically varying the concentrations of the nitrogen source. The TEM analysis also revealed that when ferrocenylaniline and ferrocene/aniline reactions are compared at similar Fe/N ratios, higher N doping levels are achieved (ca. 2-5×) when ferrocenylaniline is the catalyst.     

[Co（NH3）6]Cl3实验中制备条件对配合物形成影响的讨论

针对[Co(NH3)6]Cl3制备实验中,反应条件不同会导致生成具有不同组成的Co(Ⅲ)氨配合物这一问题,系统探讨了制备过程中在配体NH3、Cl-和H2O共存时,[Co(NH3)6]Cl3、[Co(NH3)5Cl]Cl2和[Co(NH3)5(H2O)]Cl3这三种Co(Ⅲ)氨配合物的生成条件和稳定性。通过对比分析各自的形成过程和制备条件,将化学原理应用于解释实验现象,可培养学生结合理论知识对实验案例进行对比分析的探究能力。     

Nitrite Oxidation with Copper–Cobalt Nanoparticles on Carbon Nanotubes Doped Conducting Polymer PEDOT Composite

Copper–cobalt bimetal nanoparticles (Cu?Co) have been electrochemically prepared on glassy carbon electrodes (GCEs), which were electrodeposited with conducting polymer nanocomposites of poly(3,4‐ethylenedioxythiophene) (PEDOT) doped with carbon nanotubes (CNTs). Owing to their good conductivity, high mechanical strength, and large surface area, the PEDOT/CNTs composites offered excellent substrates for the electrochemical deposition of Cu?Co nanoparticles. As a result of their nanostructure and the synergic effect between Cu and Co, the Cu?Co/PEDOT/CNTs composites exhibited significantly enhanced catalytic activity towards the electrochemical oxidation of nitrite. Under optimized conditions, the nanocomposite‐modified electrodes had a fast response time within 2 s and a linear range from 0.5 to 430 μm for the detection of nitrite, with a detection limit of 60 nm . Moreover, the Cu?Co/PEDOT/CNTs composites were highly stable, and the prepared nitrite sensors could retain more than 96 % of their initial response after 30 days.     

Design of a Prussian Blue Analogue/Carbon Nanotube Thin‐Film Nanocomposite: Tailored Precursor Preparation,Synthesis, Characterization,and Application

Multi‐walled carbon nanotubes (MWCNTs) filled with different species of cobalt (metallic cobalt, cobalt oxide) were synthesized by a chemical vapor deposition method through cobaltocene pyrolysis. A systematic study was performed to correlate different experimental conditions with the structure and characteristics of the obtained material. Thin films of Co‐filled CNTs were deposited over conductive substrates through a liquid–liquid interfacial method and were used for cobalt hexacyanoferrate (CoHCFe) electrodeposition by an innovative route in which the Co species encapsulated in the CNTs were employed as reactants. The CNT/CoHCFe films were characterized by different spectroscopic, microscopic, and electrochemical techniques and presented high electrochemical stability in different media. The nanocomposites were applied as both an electrochemical sensor to H₂O₂ and a cathode for ion batteries and showed limits of detection at approximately 3.7 nmol L ^?1 and a capacity of 130 mAh g^?1 at a current density of 5 A g^?1.