LaNiO3/Pd复合薄膜电极材料在碱性溶液中的电化学行为研究

用射频磁控溅射法在Si(111)衬底上沉积制备金属Pd膜、LaNiO3单层膜和Pd/LaNiO3复合薄膜,利用XRD,SEM,EDS能谱、四元探针和电化学方法系统研究了退火处理和表面覆Pd对Pd/LaNiO3复合薄膜电极的相组织结构、表面形貌、电学以及电化学储氢行为的影响。结果表明,700℃退火1 h后,LaNiO3薄膜具有结晶度较佳的钙钛矿型菱方结构组织和最小的电阻率(0.79 mΩ·cm),退火温度高于800℃后,LaNiO3菱方型结构组织开始分解,电阻率增加。LaNiO3薄膜在空气中退火后其表面化学吸附氧转变为晶格氧,导致LaNiO3薄膜氧元素含量明显增加。电化学测试结果表明,在碱液中金属Pd膜具有良好的析氢电催化活性和较好的电化学储氢性能,其最大放电容量为130 mAh·g-1。退火态LaNiO3单膜电极放电容量很小(27 mAh·g-1),当表面覆Pd后退火态LaNiO3/Pd复合薄膜电极放电容量增加至181 mAh·g-1,扣除其表面Pd膜吸氢容量后LaNiO3薄膜电极的实际放电容量最高达到400 mAh·g-1。LaNiO3表面镀Pd后能极大改善和提高LaNiO3薄膜电极的电催化活性和电化学储氢容量。     

氢氧化镍薄膜制备及析氧电催化活性评价的综合实验设计

设计一个包括氢氧化镍薄膜制备、铁掺杂以及析氧电催化活性评价的系统性应用化学综合实验。通过开展本实验,学生能够(1)学习利用电化学沉积方法制备电催化剂薄膜的技术;(2)初步掌握利用循环伏安、塔菲尔曲线等电化学测试技术对析氧电催化剂的活性进行评价的方法;(3)认识到痕量的杂质元素(铁)将对物质性能(析氧电催化活性)产生显著影响的客观事实。本实验将引导学生关注绿色可再生能源的开发及应用,有利于学生化学应用能力的培养。     

焦粉活性炭/Al-Ni(OH)2复合电极材料的制备及其超级容器性能

以焦粉为原料,用HNO3预处理除灰,采用KOH浸渍-煅烧活化法制备焦粉活性炭(CPAC),通过场发射扫描电子显微镜、X射线衍射等表征其形貌,采用BET测试其比表面积、孔结构及孔径分布。初步考察了活化温度、活化时间等对焦粉活性炭电极材料电化学性能的影响。采用共沉淀法制备CPAC/Al-Ni(OH)2复合电极材料,通过恒电流充放电测试及循环伏安测试表征CPAC/Al-Ni(OH)2复合电极材料的电化学性能。结果表明,当活化温度为800℃、活化时间为3 h制得的焦粉活性炭电极材料的电化学性能最佳,比电容达到211 F/g。CPAC-800℃-3 h/Al-Ni(OH)2复合电极材料随Al掺杂量的增大呈现先增大后减小的趋势。在固定Al质量掺杂量为4%,炭镍质量比为1∶1时所得复合材料的比电容量最大:1173.6 F/g。恒电流充放电及循环伏安测试表明Al掺杂量为4%、炭镍比为1∶1的复合材料具有较好的电化学性能。     

贵金属负载TiO2对光催化还原CO2选择性的影响

利用光沉积方法在TiO₂表面分别负载1%(质量分数) Pt、Pd、Au和Ag助催化剂.用TEM、XRD、UV-vis等技术对催化剂进行了表征,并利用连续瞬态电流时间响应和线性扫描伏安法等电化学方法,对贵金属负载的TiO₂光催化剂在光照条件下的电流响应强度及电催化析氢电位等特性加以测试.分析了贵金属助催化剂对光催化还原CO₂性能的差异.结果表明,负载贵金属助催化剂能显著加速光生电子空穴的分离,降低复合率;另外,助催化剂对还原CO₂选择性的顺序为Ag>Au>Pd>Pt.贵金属助催化剂还原CO₂的加氢选择性和析氢过电位存在相关性,即越不利于析氢过程的助催化剂,其催化CO₂加氢还原产物的选择性越高.     

Pd/Mm(富铈稀土)薄膜电极在KOH溶液中的电化学行为

利用磁控溅射法制备了Pd/Mm(Mischmetal)混合稀土薄膜,采用X射线衍射、AFM及循环伏安和交流阻抗谱等电化学测试技术研究了Pd/Mm稀土薄膜的晶体结构、表面形貌及其在KOH溶液中的电化学行为.结果表明,Pd/Mm薄膜表面的Pd层由纳米级的孤岛状颗粒构成,颗粒大小为100～200 nm.循环伏安法研究表明,氢的电化学氧化和还原均通过表面Pd金属层进行.Pd/Mm稀土薄膜电极的交流阻抗图由两个容抗弧组成,低频区的容抗弧对应氢在电极中的固态扩散过程,而高频段的容抗弧对应氢在电极表面的电化学还原过程,其中氢在薄膜电极内部的扩散是速率控制步骤.     

不同Co含量对纳米多孔Ni-Co结构及析氢催化性能的影响

通过真空熔炼和快速凝固的方法制备了不同Co含量的Ni-Co-Al合金,经脱合金化后得到纳米多孔Ni-Co。采用XRD、SEM、TEM、N2吸附-脱附研究了所得纳米多孔Ni-Co结构特征,以线性扫描伏安法(LSV)、交流阻抗(IMP)等手段对纳米多孔NiCo/GCE电极析氢性能进行了测试。结果表明:纳米多孔Ni-Co合金骨架表面存在尺寸更为细小的5～10 nm的小孔,Co含量(质量分数)在40%～60%时,析氢催化性能较好。     

MoS2-石墨烯的制备及其电催化析氢性能的研究

本文利用改进的Hummers方法合成层状的石墨烯,并用原位合成法在石墨烯上负载了颗粒状二硫化钼。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X-射线光电子能谱分析仪(XPS)、粉末X-射线衍射仪(XRD)、比表面及孔隙度分析仪对所合成物质的形貌、结构、比表面积及孔径进行分析;使用电化学工作站测试催化剂的线性循环伏安和Tafel曲线来分析所合成催化剂的电化学析氢性能。结果表明在所有样品中石墨烯/二硫化钼-21.7复合物的电催化性能最好,其在电流密度为-10 mA·cm~(-2)时过电位为-193 mV。     

氮掺杂碳材料负载碳化钼的合成及析氢性能研究

过渡金属碳化物被认为是一类可替代贵金属的高效电催化析~*氢反应催化剂,提升其催化性能和稳定性能获得了广泛关注和研究。本文以钼酸铵和二氰二胺为前驱体,均匀混合后利用一步高温退火法制备了氮掺杂碳材料负载碳化钼(Mo_2C-NC)的复合材料。通过透射电子显微镜,X射线粉末衍射以及X射线光电子能谱等测试对该催化剂形貌,组成及结构进行表征。电化学测试结果表明,Mo_2C-CN复合催化剂表现了优异的电催化析氢性能:当电流密度为10 mA cm~(-2)时,在酸性和碱性体系中,Mo_2C-CN催化剂的过电势分别为和130和257 mV s~(-1),并且均展示出了优异的稳定性能。     

退火温度对TiO_2/CdSe纳米片异质结薄膜光电性能的影响

采用水热法在FTO上制备(001)高活性晶面主导的TiO_2纳米片薄膜,利用循环伏安法在TiO_2纳米片薄膜上沉积CdSe颗粒,制备了TiO_2/CdSe纳米片异质结薄膜。分别在150、250、350、450℃,氩气保护气氛中对样品进行退火。利用X射线衍射仪(XRD)、场发射扫描电镜(FESEM)、X射线光电子能谱分析仪(XPS)、紫外-可见(UV-Vis)分光光度计以及电化学工作站对不同温度退火后的TiO_2/CdSe纳米片异质结薄膜的微观形貌、晶体结构、光电化学性能进行表征和测试。结果表明:六方相CdSe纳米颗粒均匀包覆在TiO_2纳米片表面,直径30 nm左右;随着退火温度的升高CdSe纳米颗粒长大,形成光滑的CdSe薄膜,且晶化程度提高;TiO_2纳米片表面的Se元素与Cd元素发生氧化;TiO_2/CdSe纳米片异质结薄膜对可见光的吸收光谱发生红移,禁带宽度逐渐减小。光电化学性能测试表明随着退火温度的升高,TiO_2/CdSe纳米片异质结薄膜的光电流密度显著提高,开路电压减小,但由于SeO_2和CdO的出现,导致填充因子减小,影响光电转换效率的提高。在本实验条件下,TiO_2/CdSe纳米片异质结薄膜的最佳退火温度为150℃,填充因子为0.77,光电转换效率达到3.12%。     

金属前驱体对质子交换膜燃料电池用PtCu/C催化剂性能的影响

采用乙二醇还原法,利用不同金属前驱体(CuSO_4/CuCl_2、K_2PtCl_4/H_2PtCl_6)制备了铂铜总质量分数为20%的四种PtCu/C催化剂,并通过透射电子显微镜(TEM)、X射线衍射(XRD)、循环伏安法(CV)和线性扫描伏安法(LSV)对催化剂进行物相结构表征及电化学性能测试。结果表明,以CuSO_4和K_2PtCl_4为前驱体组合制备出的PtCu/C催化剂性能最优。所制备的PtCu/C催化剂金属颗粒平均粒径为2.3nm,粒径范围窄,在碳载体上负载均匀;电化学活性面积(ECSA)达到73.0m2/gPt,质量比活性(MA)为126.65mA/mgPt,均优于商业Pt/C催化剂。     

Achieving Superior Electrocatalytic Performance by Surface Copper Vacancy Defects during Electrochemical Etching Process

Vacancy defects of catalysts have been extensively studied and proven to be beneficial to various electrocatalytic reactions. Herein, an ultra‐stable three‐dimensional PtCu nanowire network (NNW) with ultrafine size, self‐supporting rigid structure, and Cu vacancy defects has been developed. The vacancy defect‐rich PtCu NNW exhibits an outstanding performance for the oxygen reduction reaction (ORR), with a mass activity 14.1 times higher than for the commercial Pt/C catalyst (20 %.wt, JM), which is currently the best performance. The mass activity of the PtCu NNW for methanol oxidation reaction (MOR) is 17.8 times higher than for the commercial Pt/C catalyst. Density‐functional theory (DFT) calculations indicate that the introduction of Cu vacancies enhances the adsorption capacity of Pt atoms to the HO* intermediate and simultaneously weakens the adsorption for the O* intermediate. This work presents a facile strategy to assemble efficient electrocatalysts with abundant vacancy defects, at the same time, provides an insight into the ORR mechanism in acidic solution.     

Synthesis of CuCorePtShell Nanoparticles as Model Structures for Core–Shell Electrocatalysts by Direct Platinum Electrodeposition on Copper

The synthesis of Cu(core)Pt(shell) model catalysts by the direct electrochemical deposition of Pt on Cu particles is presented. Cu particles with an average diameter of 200 nm have been deposited on glassy‐carbon electrodes by double pulse electrodeposition from a copper sulfate solution. Subsequent deposition from a platinum nitrate solution under potential control allows for a high selectivity of the Pt deposition towards Cu. Using a combination of cyclic voltammetry, XPS and sputtering, the structure of the generated particles has been analyzed and their core–shell configuration proven. It is shown that the electrocatalytic activity for the oxygen reduction is similar to that of other PtCu catalyst systems. The synthesized structures could allow for the analysis of structure–activity relations of core–shell catalysts on the way to the simple and controlled synthesis of supported Cu(core)Pt(shell) nanoparticles as oxygen reduction catalysts.     

新型钴-聚吡咯-碳载Pt燃料电池催化剂的制备与表征

采用脉冲微波辅助化学还原法制备了钴-聚吡咯-碳(Co-PPy-C)载Pt催化剂(Pt/Co-PPy-C),其中Pt的总质量占20%.利用透射电镜(TEM)、光电子射线能谱分析(XPS)和X射线衍射(XRD)研究了催化剂的结构,用循环伏安(CV)、线性扫描伏安(LSV)等方法考察了其电化学活性及氧还原反应(ORR)动力学特性及耐久性.Pt/Co-PPy-C电催化剂的金属颗粒直径约1.8 nm,略小于商用催化剂Pt/C(JM)颗粒尺寸(约2.5 nm);催化剂在载体上分散均匀,粒径分布范围较窄.Pt/Co-PPy-C的电化学活性比表面积(ECSA)(75.1 m2·g-1)高于商用催化剂的ECSA(51.3 m2·g-1).XPS测试表明,自制催化剂表面的Pt主要以零价形式存在.而XRD结果显示,自制催化剂中Pt(111)峰最强,Pt主要为面心立方晶格.Pt/Co-PPy-C具有与Pt/C(JM)相同的半波电位;在0.9 V下,Pt/Co-PPy-C的比活性(1.21 mA·cm-2)高于商用催化剂的比活性(1.04 mA·cm-2),表现出更好的ORR催化活性.动力学性能测试表明催化剂的ORR反应以四电子路线进行.CV测试1000圈后,Pt/Co-PPy-C和Pt/C(JM)的ECSA分别衰减了13.0%和24.0%,可见自制催化剂的耐久性高于商用Pt/C(JM),在质子交换膜燃料电池(PEMFC)领域有一定的应用前景.     

新型钴-聚吡咯-碳载Pt燃料电池催化剂的制备与表征

采用脉冲微波辅助化学还原法制备了钴-聚吡咯-碳（Co-PPy-C）载Pt 催化剂（Pt/Co-PPy-C）,其中Pt 的总质量占20%. 利用透射电镜（TEM）、光电子射线能谱分析（XPS）和X射线衍射（XRD）研究了催化剂的结构,用循环伏安（CV）、线性扫描伏安（LSV）等方法考察了其电化学活性及氧还原反应（ORR）动力学特性及耐久性. Pt/Co-PPy-C电催化剂的金属颗粒直径约1.8 nm,略小于商用催化剂Pt/C（JM）颗粒尺寸（约2.5 nm）;催化剂在载体上分散均匀,粒径分布范围较窄. Pt/Co-PPy-C的电化学活性比表面积（ECSA）（75.1 m²·g^-1）高于商用催化剂的ECSA（51.3 m²·g^-1）. XPS测试表明,自制催化剂表面的Pt 主要以零价形式存在. 而XRD结果显示,自制催化剂中Pt（111）峰最强,Pt 主要为面心立方晶格. Pt/Co-PPy-C具有与Pt/C（JM）相同的半波电位;在0.9 V下,Pt/Co-PPy-C的比活性（1.21 mA·cm^-2）高于商用催化剂的比活性（1.04 mA·cm^-2）,表现出更好的ORR催化活性.动力学性能测试表明催化剂的ORR反应以四电子路线进行. CV测试1000 圈后,Pt/Co-PPy-C和Pt/C（JM）的ECSA 分别衰减了13.0%和24.0%,可见自制催化剂的耐久性高于商用Pt/C（JM）,在质子交换膜燃料电池（PEMFC）领域有一定的应用前景.     

Microstructure and electrochemically active surface area of PtM/C electrocatalysts

The results of the study of microstructural parameters and the data on the electrochemically active surface area of Pt/C and Pt₅₀M₅₀/C (M = Ni, Cu, Ag) catalysts in 1 M H₂SO₄ solutions are compared. The metal-carbon nanomaterials were prepared by the method of chemical reduction of metals from the organoaqueous solutions of their compounds. The loading of metal component in them was 30–33 wt %. It is found that actual composition of metal component in the synthesized binary systems fits best the theoretically expected one (1: 1) for the PtAg/C catalyst whereas in the PtNi/C and PtCu/C systems, a considerable fraction of alloying component is present in the form of the corresponding oxides. A decrease in the average size of crystallites of metal component from 3.8 to 1.6 nm in the series of studied materials PtAg/C > Pt/C ≥ PtCu/C s> PtNi/C does not correspond to the character of the variation of electrochemically active surface area of the catalysts: PtNi/C ≈ PtCu/C < Pt/C ≪ PtAg/C increasing from 16–20 to 62–69 m²/g(Pt). The contradiction can be caused by the preferential segregation of platinum on the surface of nanoparticles of PtAg alloy, a higher degree of agglomeration of smaller nanoparticles, and, in the case of PtNi/C and PtCu/C materials, also by the insulation of a fraction of nanoparticle surface area by the corresponding oxides.     

PtM/C (M = Ni,Cu, or Ag) electrocatalysts: effects of alloying components on morphology and electrochemically active surface areas

The microstructures of Pt/C and PtM/C (M?=?Ni, Cu, or Ag) electrocatalysts were studied using X-ray diffraction and transmission electron microscopy (TEM). The electrochemically active surface areas of the prepared materials were estimated by cyclic voltammetry in 1 M H₂SO₄. The materials, with metal contents ranging from 30 to 35 wt.%, were synthesized by chemically reducing the metal precursors in water–ethylene glycol solutions. The actual composition of the bimetallic nanoparticles corresponds to a theoretical (1:1) composition for the PtAg/C catalysts, whereas in the PtNi/C and PtCu/C materials, a portion of the alloying component exists in an oxide form. Decreasing the average metallic crystallite sizes from 3.5 to 1.6 nm does not increase the electrochemically active surface area. This apparent contradiction is because a majority of the PtNi and PtCu nanoparticles consist of 2–4 disordered crystallites. In addition, a portion of the PtNi or PtCu nanoparticle surface is covered by nickel or copper oxides, respectively. PtAg nanoparticles, which have a smaller size relative to other bimetallic particles according to the TEM data, are characterized by an intense platinum surface segregation. The agglomeration processes are lowest for the PtAg nanoparticles.     

Carbon black supported PtCu nanoparticles derived from mix-phased Cu precursor for high-performanced oxygen reduction reaction in acid medium

Alloying high-cost Pt with transition metals has been considered as an effective route to synthesize the electrocatalysts with low Pt loading and excellent activity towards oxygen reduction reaction (ORR) under acid solution. The galvanic replacement method, as featured with efficiency and simplicity, is widely reported to produce Pt-based bimetallic alloys and thereby declare the significance of reductive transition metal precursor on the enhancement of ORR performance. Herein, mix-phased Cu−Cu₂O precursor was applied to prepare carbon black supported highly dispersed PtCu alloy nanoparticles (PtCu/C). The proper Cu−Cu₂O ratios can exactly facilitate the generation of small sized PtCu alloy nanoparticles with regulated bimetallic content. Meanwhile, the Cu₂O phase is revealed to benefit the electron transfer from Pt to Cu and thus improve the intrinsic activity of Pt active sites. And the metallic Cu can favor the promotion of electrochemical active surface area. Consequently, the as-prepared PtCu/C behaves impressive ORR activity with half-wave potential of 0.88 V (vs. RHE) and mass activity of 0.49 A cm⁻² mg_Pt⁻¹ at 0.8 V, which is 9.8 times of commercial Pt/C catalysts. Our work will offer helpful advices for the development and regulation of novel Pt-based alloy materials towards diverse electrocatalysis.     

Cu(PPh3)2BH4作还原剂制备PtCu/C催化剂催化烯烃硅氢 加成反应研究

采用湿法浸渍, Cu(PPh3)2BH4作为还原剂制备了负载型PtCu/C双金属催化剂, Pt∶Cu原子比为0.5～2.0. 用于苯乙烯与三乙氧基硅烷加成反应, Cu元素的引入使Pt/C催化剂的催化性能得到提高, 表现出比Speier催化剂、Karestedt催化剂和Pt/C催化剂更好的β-加成产物选择性. 催化直链烯烃与三乙氧基硅烷加成反应表现出优良的催化性能, 并且催化剂可重复使用.     

凹形树突状PtCu纳米催化剂的合成及对甲醇的电催化

以邻苯二胺为表面活性剂,通过水热釜法一步制备凹形树突状PtCu双金属纳米催化剂(PtCu NCDs)。PtCu NCDs在电催化甲醇氧化(MOR)的应用中表现出非常高的活性和很强的抗有毒中间体作用。PtCu NCDs对于甲醇氧化的质量活性为(0.53 A·mg^-1 Pt)是商业Pt/C(0.26 A·mg^-1 Pt)的2.04倍。从比活性的CV曲线图对比发现PtCu NCDs(1.07 mA·cm^-2)是商业Pt/C(0.55 mA·cm^-2)的1.95倍。而且,PtCu NCDs(2.76)比商业Pt/C催化剂(1.02)表现出更高的I_f/I_b比值。这些优异的电催化活性可能归功于PtCu NCDs特殊的凹形树突状形貌。