Name: synthesis and performance characterizations of transition metal single atom catalyst for electrochemical co2 reduction
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这项工作得到了哈佛大学罗兰研究所的罗兰研究员计划的支持。这项工作是在纳米系统中心 (CNS) 的一部分进行的, 这是国家纳米技术基础设施网络的一个成员, 它得到国家科学基金会的支持。ECS-0335765。中枢神经系统是哈佛大学的一部分。

1. 镍单原子催化剂的制备 (GS)
<ol><li>静电纺丝前体溶液的制备<ol>
<li>取20毫升闪烁瓶, 溶解0.5 克聚丙烯腈 (Mw= 15万), 0.5 克 polypyrrolidone (Mw= 130万), 0.5 克 Ni (无3)2· 6H2O, 0.1 毫升氰 (DCDA)甲基酰胺 (DMF)。</li>
		<li>将 DMF 混合物加热到80摄氏度, 将混合物保持在80摄氏度, 持续搅拌直至所有聚合物和盐溶解, 并观察到一个清晰的溶液。</li>
	</ol>
</li>
	<li>静电纺丝生产高分子纤维<ol>
<li>设置传统的静电纺丝参数为:15 伏的静电电压, 15 厘米的气隙距离, 集衬底 8 x 8 厘米碳纤维纸 (CFP) 与-4 伏电压。</li>
		<li>提取5毫升的前体溶液成5毫升注射器, 启动注射器泵的流速为1.2 毫升 h−1, 然后启动静电纺丝。 注: 采用高压静电纺丝。尽管在纺纱过程中, 系统的电流很低, 但还是提出了一个隔热的木柜。</li>
		<li>当静电纺丝工艺完成后, 取出 CFP 基体。聚合物纤维膜覆盖 CFP 表面。</li>
	</ol>
</li>
	<li>将聚合物纤维退火成碳纳米管<ol>
<li>将所制备的聚合物纤维薄膜/CFP 在箱式炉内1.5 小时内加热至300摄氏度, 并保持0.5 小时的温度以氧化聚合物。 注: 氧化过程后, 纳米纤维 (NFs) 是自分离的碳纸产生的独立薄膜。</li>
		<li>用剪刀把这些纳米纤维切成小块 (0.5 厘米 x 2cm), 然后把它们放进石英船里。</li>
		<li>将石英船放入管式炉内, 并将其 deaerate 在形成气体 (5% H2的 Ar) 大气中。保持气体流量为 100 sccm 和压力为 1 Tor。</li>
		<li>在10分钟内加热至300摄氏度, 2 h 斜向750摄氏度, 在那里保持另1小时, 然后自然降温。</li>
	</ol>
</li>
	<li>球磨机作为合成的5分钟到纳米粉催化和表征的一般 GS 催化剂。</li>
</ol>2. 电化学 CO2还原测量
<ol><li>电池和电极<ol>
<li>要准备 0.1 M KHCO3电解质为以下测量, 首先溶化 2.5 g KHCO3在250毫升纯净的水, 然后通过电解净化电解质用二个石墨杆在 0.1 mA 为 24 h 去除任何痕量金属离子。</li>
		<li>采用新鲜 (电化学) 抛光玻碳 (1 厘米 x 2 厘米), 并覆盖其背面与电化学惰性, 疏水性蜡, 作为工作电极基板。</li>
		<li>采取4毫升闪烁瓶, 混合5毫克的正准备的 GS 催化剂与1毫升乙醇和100µL 的离子溶液 (5% 在 2-proponal) 在瓶内, 油脂实验20分钟得到一个均匀的催化剂墨水悬浮。</li>
		<li>吸管80µL 的催化剂墨水到 2 cm2玻碳表面 (0.2 毫克 cm-2质量装货) 和真空干燥催化剂被盖的电极在干燥在使用之前。</li>
		<li>分别使用铂箔和饱和甘汞电极 (SCE) 作为计数器和参考电极。</li>
		<li>使用自定义的气密 H 型玻璃细胞, 由质子交换膜分离, 用于上述3电极组装以及电化学测试运行。</li>
		<li>将工作电极和 SCE 参考电极放在 H 细胞的一个隔间中, 并将 Pt 箔电极置于另一腔内。在 H 细胞的每个隔间注入25毫升的电解质。</li>
		<li>将 H 细胞中的3电极连接到电化学工作台进行潜在控制。</li>
		<li>将电解液与 n2在 50.0 sccm (由质量流控制器监视) 中气泡30分钟向 N2饱和 0.1 M KHCO3。</li>
		<li>选择循环伏安法 (CV) 技术在 EC 实验室软件, 设置 "E 范围 (潜力)" 作为 "-10 v 到 10 v", "I 范围 (当前)" 作为 "自动", 执行5连续 CV 扫描从-0.5 v 到-1.8 V (vs. SCE) 扫描率为 50 mV/秒在 N2-饱和 0.1 M KHCO3。</li>
		<li>更改为 50 sccm CO2气体流, 等待30分钟向 CO2饱和 0.1 M KHCO3电解质, 并保持相同的 CO2流贯穿以下电解。</li>
		<li>在 EC 实验室软件中选择 CV 技术, 将 "E 范围 (潜在)" 设置为 "-10 v 到 10 v", "I 范围 (当前)" 作为 "自动", 执行5连续 CV 扫描从-0.5 v 到-1.8 V (与 SCE) 在 CO2饱和 0.1 M KHCO3的扫描率 50 mV/秒。</li>
		<li>使用 ph 计来确定电解质的 ph 值, i. e, 0.1 M KHCO3饱和的 N2或 CO2。</li>
		<li>使用 e (vs) = e (vs SCE) + 0.244 V + 0.0591 x pH 值, 将与 sce 相对应的所有电位转换为可逆氢电极刻度。</li>
		<li>通过选择恒电位电化学阻抗谱 (PEIS) 技术, 在 EC 实验室软件中确定解决方案电阻 (R u), 然后将频率范围从 0.1 Hz 设置为200赫, 记录电阻值.</li>
		<li>手动补偿ir降为 e (ir 校正 vs) = e (vs) Ru x I (安培平均电流)。</li>
	</ol>
</li>
	<li>CO2还原产品在线气相色谱分析 (GC)<ol>
<li>采用 GC, 配以分子筛5A 和 micropacked 柱的组合, 用于 CO2RR 期间的气体产品分析。 注意: 在附加的材料表中可以找到详细的 GC 列类型。</li>
		<li>使用导热系数检测器 (TCD) 来量化 H2浓度, 和一个火焰电离探测器 (methanizer), 以定量分析 CO 含量和/或任何其他烷烃物种。</li>
		<li>对 H2和 CO 浓度的校准曲线使用两种不同标准气体 (h2: 100 和 1042 ppm;CO: 100 和 496.7 ppm;与氩气平衡)。</li>
		<li>在电解过程中, 维护 co2气体流速在 50.0 sccm, 将 co2传递到包含 co2饱和 0.1 M KHCO3电解质的阴极间隔, 并将排气口排放到 GC 中。</li>
		<li>逐步调整工作电极上的电压, 范围从-0.3 到-1.0 伏, 每个电位保持15分钟, 并记录相应的 chronoamperimetric 曲线。</li>
		<li>分别测定 TCD 和 FID 信号排气中的 H2和 CO 含量。 注: 气体产品在每种电位下连续电解10分钟后取样。50 sccm CO2气体与连续产生的 H2和 CO 混合, 在电解过程中流经 GC 的取样回路 (1 毫升)。</li>
		<li>计算给定气体产品的局部电流密度, 如下所示: <img alt="Equation" src="/files/ftp_upload/57380/57380eq2.jpg"> 其中xi 是由来自两个标准气体样本 (斯科特和 Airgas) 的校准曲线所参照的在线 GC 确定的某些产品的体积分数, v是 50 sccm 的流量, ni 是数字涉及的电子, p0 = 101.3 帕, F是法拉第常数, R 是气体常数。</li>
		<li>在每个潜在的中计算相应的法拉第效率 (FE). <img alt="Equation" src="/files/ftp_upload/57380/57380eq7.jpg"> </img> 注: 由于气体流速、电流密度、气相浓度分析等误差, 整体法拉第效率可在90至110% 范围内。</li>
	</ol>
</li>
</ol>

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在上述静电纺丝过程中, 在材料合成过程中应注意两个重要步骤: 1) 加热 DMF 混合物 (步进 1.1.2) 和 2) 泵速调整 (步进 1.2.2) 以匹配纺丝速率。图 1A中的 SEM 图像显示了获得的碳纳米纤维相互连接 (直径约200纳米)。它们被分成了小块, 通过球铣削来进行刻画, 如图 1B所示。纳米粒子在碳纳米纤维中均匀分布。在高温下, 用镍合金化的碳原子会析出, 并在冷却过...

将 CO2转换为化学品或使用清洁电的燃料变得越来越重要, 作为一种潜在的途径, 以防止进一步 CO2排放1,2,3,4, 5,6。然而, 由于高动能障碍和与氢进化反应 (她) 在水中的竞争而导致 co2还原反应 (co2RR) 的低活动性和选择性, 这一实际应用目前受到挑战。媒体。大多数传统的过渡金属催化剂, 如 Fe、Co 和镍, 由于其精湛的活动78, 表现出低 Co2RR 选择性。有效调整其材料性能以改变这些过渡金属催化剂的反应通路, 对于提高它们的 CO2RR 选择性至关重要。在改变催化剂电子性能的不同方法中, 将金属原子分散到单原子形态中, 由于它们的催化行为与体积相对应显著地变化, 因而受到了强烈的关注。9,10,11. 然而, 由于无界原子的高机动性, 在不存在支持材料的情况下获得单一金属原子是相当有挑战性的。因此, 有必要建立一个与过渡金属原子进行限制和协调的缺陷的主矩阵材料。这可能开辟了新的机会: 1) 调整过渡金属的电子性质为 CO2RR 活动站点, 和 2) 同时保持相对简单的原子协调为基础机制研究。此外, 那些被困在密闭环境中的过渡金属原子在催化过程中不能轻易移动, 防止在许多情况下观察到的表面原子成核或重建12,13 ,14。
二维层状石墨烯作为金属单原子的宿主, 由于其高的电子电导率、化学稳定性和惰性对 CO2的还原和她的催化反应特别感兴趣。更重要的是, 铁、钴和镍金属被称为能够催化在其表面的碳石墨化过程15。简而言之, 这些过渡金属在高温热退火过程中会产生碳合金。当温度下降时, 碳开始从合金化阶段沉淀出来, 并被催化在过渡金属表面形成石墨烯层。在此过程中, 随着石墨烯缺陷的产生, 金属单原子将被困在这些石墨烯缺陷作为 CO2RR16,17,18,19的活动站点。在这里, 我们报告这一详细的协议, 旨在帮助新的从业者在单原子催化领域, 以及提供一个明确的示范在线 CO2减少产品分析。更多信息可以在我们最近发布的文章19和一系列相关工作20,21,22,23中找到。

<table><tbody><tr><td>syringe pump&amp;nbsp;</td><td>KD Scientific</td><td>KDS-100</td><td></td></tr><tr><td>tube furnance</td><td>Lindberg/Blue M</td><td>TF55035A-1</td><td></td></tr><tr><td>ball miller</td><td>SPEX SamplePrep</td><td>5100</td><td></td></tr><tr><td>electrochemical work station</td><td>BioLogic</td><td>VMP3</td><td></td></tr><tr><td>pH meter</td><td>Orion</td><td>320 PerpHecT&amp;nbsp;</td><td>2 points calibration before use</td></tr><tr><td>gas chromatograph</td><td>Shimadzu</td><td>GC-2014</td><td>a combined seperation system consisting of molecular sieve 5A, Hayesep Q, Hayesep T, and Hayesep N</td></tr><tr><td>mass flow controller</td><td>Alicat Scientific&amp;nbsp;</td><td>MC-50SCCM-D/5M</td><td></td></tr><tr><td>ultrapure water system</td><td>Millipore</td><td>Synergy</td><td></td></tr><tr><td>vacuum desiccator&amp;nbsp;</td><td>PolyLab</td><td>55205</td><td></td></tr><tr><td>polyacrylonitrile</td><td>Sigma-Aldrich</td><td>181315</td><td>M&lt;sub&gt;w&lt;/sub&gt;=150,000</td></tr><tr><td>polypyrrolidone</td><td>Sigma-Aldrich</td><td>437190</td><td>M&lt;sub&gt;w&lt;/sub&gt;=1,300,000</td></tr><tr><td>Ni(NO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;6H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma-Aldrich</td><td>244074</td><td></td></tr><tr><td>dicyandiamide</td><td>Sigma-Aldrich</td><td>D76609</td><td></td></tr><tr><td>dimethylformamide</td><td>Sigma-Aldrich</td><td>227056</td><td></td></tr><tr><td>carbon fiber paper&amp;nbsp;</td><td>AvCarb</td><td>MGL370</td><td></td></tr><tr><td>Nafion 117 membrane</td><td>Fuel Cell Store</td><td>117</td><td>used as proton exchange membrane in H-cell</td></tr><tr><td>KHCO&lt;sub&gt;3&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>431583</td><td>further purified by electrolysis</td></tr><tr><td>platinum foil&amp;nbsp;</td><td>Beantown Chemical</td><td>126580</td><td></td></tr><tr><td>saturated calomel electrode</td><td>CH Instruments</td><td>CHI150</td><td></td></tr><tr><td>glassy carbon electrode</td><td>HTW GmbH</td><td>SIGRADUR</td><td>1 cm &amp;times; 2 cm</td></tr><tr><td>wax</td><td>Apiezon</td><td>W-W100</td><td></td></tr><tr><td>Nafion 117 solution</td><td>Sigma-Aldrich</td><td>70160</td><td>used as ionomer in catalyst ink preparation&amp;nbsp;</td></tr><tr><td>forming gas</td><td>Airgas</td><td>UHP</td><td>5% H&lt;sub&gt;2&lt;/sub&gt; balanced with Ar</td></tr><tr><td>carbon dioxide</td><td>Airgas</td><td>LaserPlus</td><td></td></tr><tr><td>sandard gas</td><td>Airgas</td><td>customized</td><td>500 ppm CO, 500 ppm CH&lt;sub&gt;4&lt;/sub&gt;, 1000 ppm H&lt;sub&gt;2&lt;/sub&gt; balanced with Ar</td></tr><tr><td>sandard gas</td><td>Air Liquide</td><td>customized</td><td>100 ppm H&lt;sub&gt;2&lt;/sub&gt;, 100 ppm CO and other alkanes balanced with Ar</td></tr></tbody></table>

synthesis and performance characterizations of transition metal single atom catalyst for electrochemical co2 reduction

该协议既提供了镍单原子催化剂的合成方法, 又介绍了其在水 CO2还原中的催化活性和选择性的电化学检测。与传统金属纳米晶不同的是, 金属单原子的合成涉及一种基体材料, 它可以限制这些单一原子并防止它们聚集。我们报告的静电纺丝和热退火方法, 以准备镍单原子分散和协调在石墨烯壳, 作为活性中心的 co2减少到 co。在合成过程中, N 掺杂在产生石墨烯空缺以捕获 Ni 原子方面起着关键作用。采用畸变校正扫描透射电镜和三维原子探针层析成像技术识别石墨烯空缺中的单个镍原子点。同时还介绍了电化学 CO2还原装置与在线气相色谱联用的详细设置。与金属镍相比, 镍单原子催化剂显著改善 CO2的还原和抑制 H2演化侧反应。

扫描电镜 (SEM), 扫描透射电镜 (茎) 和能量色散 X 射线光谱学 (EDX) 映射图像, 显示在图 1中的形态学特征的 GS。三维原子探针层析成像 (3 维易测) 结果显示在图 2中, 用于直接识别单个 Ni 站点分布及其邻近的化学环境。在线电化学 GC 测量的设置和结果显示在图 3中, 用于量化 CO2RR 气体产品。
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Watch this Scientific Journal Video about Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction at JoVE.com

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

电化学 CO2还原的过渡金属单原子催化剂的合成及性能表征

在这里, 我们提出了一个协议, 以合成和电化学测试的过渡金属在石墨烯空缺协调合作的活性中心, 选择性二氧化碳还原到一氧化碳的水溶液。

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...

synthesis-performance-characterizations-transition-metal-single-atom

Universidad San Sebastian

Research

JoVE Journal

Chemistry

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

18.0K 次观看.  Harvard University. 在这里, 我们提出了一个协议, 以合成和电化学测试的过渡金属在石墨烯空缺协调合作的活性中心, 选择性二氧化碳还原到一氧化碳的水溶液。

视频: Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 &#176;C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder.

A &#8220;removable ceramic coating method&#8221; is presented in visual format for the synthesis of non-sintered and metal-terminated monometallic and bimetallic early transition metal carbide and nitride nanoparticles with tunable sizes and crystal structures.

单金属和双金属前过渡金属碳化物和氮化物纳米粒子的反相微乳液介导的合成

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The ...

科研

化学

On the Preparation and Testing of Fuel Cell Catalysts Using the Thin Film Rotating Disk Electrode Method

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a high surface area carbon, and to test their performance in thin film rotating disk electrode (TF-RDE) measurements. The TF-RDE methodology is widely used for catalyst screening; nevertheless, the measured performance sometimes considerably differs among research groups. These uncertainties impede the advancement of new catalyst materials and, consequently, several authors discussed possible best practice methods and the importance of benchmarking.
The visual tutorial highlights possible pitfalls in the TF-RDE testing of Pt/C catalysts. A synthesis and testing protocol to assess standard Pt/C catalysts is introduced that can be used together with polycrystalline Pt disks as benchmark catalysts. In particular, this study highlights how the properties of the catalyst film on the glassy carbon (GC) electrode influence the measured performance in TF-RDE testing. To obtain thin, homogeneous catalyst films, not only the catalyst preparation, but also the ink deposition and drying procedures are essential. It is demonstrated that an adjustment of the ink&#39;s pH might be necessary, and how simple control measurements can be used to check film quality. Once reproducible TF-RDE measurements are obtained, determining the Pt loading on the catalyst support (expressed as Pt wt%) and the electrochemical surface area is necessary to normalize the determined reaction rates to either surface area or Pt mass. For the surface area determination, so-called CO stripping, or the determination of the hydrogen underpotential deposition (Hupd) charge, are standard. For the determination of the Pt loading, a straightforward and cheap procedure using digestion in aqua regia with subsequent conversion of Pt(IV) to Pt(II) and UV-vis measurements is introduced.

Preparing and testing Pt/C fuel cell catalysts is subject to continuous discussion in the scientific community with respect to reproducibility and best practice. With the presented work, we intend to present a step-by-step tutorial to make and test Pt/C catalysts, which can serve as benchmark for novel catalyst systems.

用薄膜旋转圆盘电极法制备和测试燃料电池催化剂的研究

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a ...

环境科学

Simple Methods for the Preparation of Non-noble Metal Bulk-electrodes for Electrocatalytic Applications

The rock material pentlandite with the composition Fe4.5Ni4.5S8 was synthesized via high temperature synthesis from the elements. The structure and composition of the material was characterized via powder X-ray diffraction (PXRD), M&#246;ssbauer spectroscopy (MB), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and energy dispersive X-ray spectroscopy (EDX). Two preparation methods of pentlandite bulk electrodes are presented. In the first approach a piece of synthetic pentlandite rock is directly contacted via a wire ferrule. The second approach utilizes pentlandite pellets, pressed from finely ground powder, which is immobilized in a Teflon casing. Both electrodes, whilst being prepared by an additive-free method, reveal high durability during electrocatalytic conversions in comparison to common drop-coating methods. We herein showcase the striking performance of such electrodes to accomplish the hydrogen evolution reaction (HER) and present a standardized method to evaluate the electrocatalytic performance by electrochemical and gas chromatographic methods. Furthermore, we report stability tests via potentiostatic methods at an overpotential of 0.6 V to explore the material limitations of the electrodes during electrolysis under industrial relevant conditions.

A facile preparation method of electrodes using the bulk material Fe4.5Ni4.5S8 is presented. This method provides an alternative technique to conventional electrode fabrication and describes prerequisites for unconventional electrode materials including a straightforward electrocatalytic testing method.

用于制备用于电催化应用的非贵金属体电极的简单方法

The rock material pentlandite with the composition Fe4.5Ni4.5S8 was synthesized via high temperature synthesis from the elements. The structure and ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

铂镍纳米线的合成及减氧性能优化

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

化学沉淀法合成铌2O5改性高比表面积镍催化剂

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic polymers, with the aim of photo-activating oxygen-evolving manganese oxide catalysts, which are important components in artificial photosynthesis. The cross-linking technique was applied to obtain a self-standing membrane with a high PW12O403- content. Incorporation and structure retention of PW12O403- within the polymer matrix were confirmed by FT-IR and micro-Raman spectroscopy, and optical characteristics were investigated by UV-Vis spectroscopy, which revealed successful construction of the metal-to-metal charge transfer (MMCT) unit. After deposition of MnOx oxygen evolving catalysts, photocurrent measurements under visible light irradiation verified the sequential charge transfer, Mn &#8594; MMCT unit &#8594; electrode, and&#160;the photocurrent intensity was consistent with the redox potential of the donor metal (Ce or Co). This method provides a new strategy for preparing integrated systems involving catalysts and photon-absorption parts for use with photo-functional materials.

Here, we present a protocol to prepare charge transfer chromophores based on a polyoxometalate/polymer composite membrane.

氧化锰催化剂光活化 Polyoxometalate 基光响应膜的制备

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic ...

Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics

A significant number of heterogeneously-catalyzed chemical processes occur under liquid conditions, but simulating catalyst function under such conditions is challenging when it is necessary to include the solvent molecules. The bond breaking and forming processes modeled in these systems necessitate the use of quantum chemical methods. Since molecules in the liquid phase are under constant thermal motion, simulations must also include configurational sampling. This means that multiple configurations of liquid molecules must be simulated for each catalytic species of interest. The goal of the protocol presented here is to generate and sample trajectories of configurations of liquid water molecules around catalytic species on flat transition metal surfaces in a way that balances chemical accuracy with computational expense. Specifically, force field molecular dynamics (FFMD) simulations are used to generate configurations of liquid molecules that can subsequently be used in quantum mechanics-based methods such as density functional theory or ab initio molecular dynamics. To illustrate this, in this manuscript, the protocol is used for catalytic intermediates that could be involved in the pathway for the decomposition of glycerol (C3H8O3). The structures that are generated using FFMD are modeled in DFT in order to estimate the enthalpies of solvation of the catalytic species and to identify how H2O molecules participate in catalytic decompositions.

The goal of the protocol presented here is to generate and sample trajectories of configurations of liquid water molecules around catalytic species on a flat transition metal surface. The sampled configurations can be used as starting structures in quantum mechanics-based methods.

利用密度泛函理论和力场分子动力学对多相水-金属催化剂接口进行多尺度采样

A significant number of heterogeneously-catalyzed chemical processes occur under liquid conditions, but simulating catalyst function under such conditions ...

Tuning the Acidity of Pt/ CNTs Catalysts for Hydrodeoxygenation of Diphenyl Ether

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid nanosheets, a series of Pt/xHMNO6/CNTs with different solid acid compositions (x = 5, 20 wt%; M = Nb, Ta; N = Mo, W) have been prepared by carbon nanotube pretreatment, protonic exchange, solid acid exfoliation, aggregation and finally Pt particles impregnation. The Pt/xHMNO6/CNTs are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and NH3-temperature programmed desorption. The study revealed that HNbWO6 nanosheets were attached on CNTs, with some edges of the nanosheets being bent in shape. The acid strength of the supported Pt catalysts increases in the following order: Pt/CNTs &#60; Pt/5HNbWO6/CNTs &#60; Pt/20HNbMoO6/CNTs &#60; Pt/20HNbWO6/CNTs &#60; Pt/20HTaWO6/CNTs. In addition, the catalytic hydroconversion of lignin-derived model compound: diphenyl ether using the synthesized Pt/20HNbWO6 catalyst has been investigated.

A protocol for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs is presented.

调整二苯醚氢氧化的Pt/CNT催化剂的酸度

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid ...

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products and notably to generate chiral carbon centers. The crucial first step consists in the selective double hydroboration of CO2 catalyzed by an iron hydride complex. The product obtained with this 4 e- reduction is a rare bis(boryl)acetal, compound 1, which is subjected in situ to three different reactions in a second step. The first reaction concerns a condensation reaction with (diisopropyl)phenylamine affording the corresponding imine 2. In the second and third reaction, intermediate 1 reacts with triazol-5-ylidene (Enders&#39; carbene) to afford compounds 3 or 4, depending on the reaction conditions. In both compounds, C-C bonds are formed, and chiral centers are generated from CO2 as the only source of carbon. Compound 4 exhibits two chiral centers obtained in a diastereoselective manner in a formose-type mechanism. We proved that the remaining boryl fragment plays a key role in this unprecedented stereocontrol. The interest of the method stands on the reactive and versatile nature of 1, giving rise to various complex molecules from a single intermediate. The complexity of a two-step method is compensated by the overall short reaction time (2 h for the larger reaction time), and mild reaction conditions (25 &#176;C to 80 &#176;C and 1 to 3 atm of CO2).

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations are conducted in a one-pot two-step procedure for the synthesis of complex molecules. The selective 4 e- reduction of CO2 with a hydroborane reductant affords a reactive and versatile bis(boryl)acetal intermediate which is subsequently involved in condensation reaction or carbene-mediated C-C coupling generation.

多功能 CO2转化为复杂产品:单罐两步战略

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products ...

Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented herein. The novel strategy is based on a facile one-pot pyrolysis treatment of cobalt (II) acetylacetonate and nitrogen-rich organic precursors under Ar atmosphere at 800 &#176;C, resulting in the formation of Co- and N- co-doped carbon nanotube with earthworm-like morphology. The obtained catalyst was found to have a high density of defect sites, as confirmed by Raman spectroscopy. Here, cobalt (II) nanoparticles were stabilized on the atomically dispersed cobalt- and nitrogen-doped carbon nanotubes. The catalyst was confirmed to be effective in the catalytic hydrolysis of ammonia borane, in which the turnover frequency was 5.87 mol H2&#183;molCo-1&#183;min-1, and the specific hydrogen generation rate was determined to be 2447 mL H2&#183;gCo-1&#183;min-1. A synergistic function between the Co nanoparticle and the doped carbon nanotubes was proposed for the first time in the catalytic hydrolysis of ammonia borane reaction under a mild condition. The resulting hydrogen production with its high energy density and minimal refueling time could be suitable for future development as energy sources for mobile and stationary applications such as road trucks and forklifts in transport and logistics.

Here, we present a protocol to synthesize Co nanoparticles supported on carbon nanotubes with Co- and N- dopants for hydrogen productions.

碳纳米管负载掺杂Co和N原子金属纳米粒子的合成及其在制氢中的催化应用

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented ...

电化学 CO₂还原的过渡金属单原子催化剂的合成及性能表征

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