牺牲模板法制备空心结构钯纳米粒子/石墨烯复合体及其甲酸电氧化性能研究

通过Pd Cl42-与Co之间发生简单的置换反应,在表面活性剂PVP的作用下,成功地制备出由3 nm的Pd纳米粒子组成的空心结构Pd纳米球结构,将其命名为Pd-NS。随后,以石墨烯(GN)作为载体,将Pd-NS负载在GN的表面制备了Pd-NS/GN催化剂。在甲酸电氧化催化反应中,Pd-NS/GN催化剂表现出较大的电化学比表面积、良好的电催化性能以及较高的稳定性。     

AgPd双金属纳米空心球的合成及其催化性能

以Ag纳米颗粒为牺牲模板,H₂PdCl₄为前驱体,抗坏血酸为还原剂,聚乙烯吡咯烷酮为表面活性剂,在70 ℃下采用电偶置换法结合还原法制备出AgPd双金属纳米空心球。采用紫外可见光谱、粉末X射线衍射、透射电镜结合能量色散等手段对由不同体积的0.01 mol·L^-1 H₂PdCl₄溶液制备的产物进行结构表征。结果表明,随着H₂PdCl₄溶液体积的增加,产物的空心化程度逐渐升高,晶粒的尺寸逐渐增大。当 H₂PdCl₄溶液体积为 120 μL时,合成的 AgPd双金属纳米空心球组成和结构较为均匀,其粒径约为 25 nm,壳层厚度 2~3 nm。双金属中,由于 Ag 和 Pd 电负性的差异,电子从 Ag 转移到了 Pd,使 Pd 表面出现电子富集区,显著提高了其催化效率。将所合成的AgPd双金属以及纯金属Ag和Pd作为催化剂,分别用于硼氢化钠催化还原4-硝基苯酚的反应,发现AgPd双金属的催化性能远高于纯金属Ag和Pd,其中AgPd-120纳米空心球(H₂PdCl₄溶液体积120 μL)作催化剂时的反应速率常数最高,是同等尺寸纯Ag纳米球的24.0倍,纯Pd纳米立方体的14.7倍。     

AgPd双金属纳米空心球的合成及其催化性能

以Ag纳米颗粒为牺牲模板,H₂PdCl₄为前驱体,抗坏血酸为还原剂,聚乙烯吡咯烷酮为表面活性剂,在70℃下采用电偶置换法结合还原法制备出AgPd双金属纳米空心球。采用紫外可见光谱、粉末X射线衍射、透射电镜结合能量色散等手段对由不同体积的0.01 mol·L^-1 H₂PdCl₄溶液制备的产物进行结构表征。结果表明,随着H₂PdCl₄溶液体积的增加,产物的空心化程度逐渐升高,晶粒的尺寸逐渐增大。当H₂PdCl₄溶液体积为120 μL时,合成的AgPd双金属纳米空心球组成和结构较为均匀,其粒径约为25 nm,壳层厚度2~3 nm。双金属中,由于Ag和Pd电负性的差异,电子从Ag转移到了Pd,使Pd表面出现电子富集区,显著提高了其催化效率。将所合成的AgPd双金属以及纯金属Ag和Pd作为催化剂,分别用于硼氢化钠催化还原4-硝基苯酚的反应,发现AgPd双金属的催化性能远高于纯金属Ag和Pd,其中AgPd-120纳米空心球(H₂PdCl₄溶液体积120 μL)作催化剂时的反应速率常数最高,是同等尺寸纯Ag纳米球的24.0倍,纯Pd纳米立方体的14.7倍。     

碳纳米管负载的Pd-Ag-Sn催化剂对甲酸的电氧化

采用硼氢化钠还原的方法合成了碳纳米管负载的钯基纳米催化剂（Pd/CNT,Pd₇Ag₃/CNT,Pd₇Sn₂/CNT,Pd₇Ag₁Sn₂/CNT,Pd₇Ag₂Sn₂/CNT和Pd₇Ag₃Sn₂/CNT）。通过XRD,TEM和XPS对其进行了表征,结果表明,相比Pd/CNT和Pd-Ag（或Pd-Sn）催化剂的纳米颗粒,Pd-Ag-Sn催化剂展现出了更小的平均颗粒尺寸（2.3 nm）。此外,还通过循环伏安（CV）和计时电流法（CA）测试了这些催化剂对甲酸氧化的电活性,在酸碱介质中,Pd-Ag-Sn/CNT对甲酸氧化都表现出了更高的电流密度。其中,Pd₇Ag₂Sn₂/CNT催化剂在酸碱介质中的电流密度分别是108.8和211.3 mA·cm^-2,相应的Pd质量电流密度高达1 364和2 640 mA·mg^-1,远远高于商业Pd/C,表明Pd-Ag-Sn/CNT催化剂对甲酸氧化表现出了极好的电催化活性。     

CuPd/MgO室温高效催化甲醛溶液产氢

采用浸渍还原法制备了MgO负载纳米CuPd合金的复合催化剂(CuPd/MgO)。该催化剂在室温催化甲醛溶液重整产氢过程中表现出优异的催化性能,转换频率(TOF)高达812.6h^-1,分别是相同条件下Cu/MgO(TOF=356.7h^-1)和Pd/MgO(TOF=34.8h^-1)的2.3倍和23倍。基于实验测试和表征结果,发现CuPd/MgO催化剂中纳米CuPd合金与表面富集缺陷的MgO载体之间存在金属-载体强相互作用。这种相互作用能够促进氧气在催化剂表面吸附活化并生成活性氧物种(超氧阴离子自由基,·O₂^-),·O₂^-先后促进甲醛中的C—H键断裂和水分子的解离,随后与反应体系中生成的质子及氢自由基(·H)依次结合,最终实现氢气的析出与氧气的再生。     

在一维ZnO表面可控构建Co3Mn1纳米晶及其催化CO氧化性能

利用热分解法制备了结构明确的负载型纳米晶催化剂。在纳米晶成核和生长过程中加入一维ZnO纳米棒作为晶种,调控不同组分的纳米晶在 ZnO纳米棒表面均匀生长,从而获得了结构明确的 MnO/ZnO、Co₃O₄/ZnO、Co₃Mn₁/ZnO催化剂。透射电子显微镜(TEM)与 X 射线粉末衍射(XRD)结果显示,不同组分纳米颗粒都均匀分散在 ZnO 纳米棒表面。相对于 MnO/ZnO 和Co₃O₄/ZnO催化剂,Co₃Mn₁/ZnO催化剂在CO氧化反应中具有最佳的催化性能。在200 L·g_cat^-1·h^-1的气时空速下,Co₃Mn₁/ZnO催化剂起活温度为 50 ℃,其 T100(CO 转化率达到 100% 时的温度)为 200 ℃;利用 X 射线光电子能谱(XPS)对不同催化剂进行了分析,结果显示,Co₃Mn₁/ZnO催化剂的氧空位比MnO/ZnO催化剂提高了30%以上,从而使其具有较高的CO氧化催化性能。更为重要的是,Co₃Mn₁/ZnO复合纳米晶催化剂的活化能(39.4 kJ·mol^-1)远低于其它负载型纳米晶催化剂。     

CuPd/MgO室温高效催化甲醛溶液产氢

采用浸渍还原法制备了MgO负载纳米CuPd合金的复合催化剂(CuPd/MgO)。该催化剂在室温催化甲醛溶液重整产氢过程中表现出优异的催化性能,转换频率(TOF)高达812.6 h^-1,分别是相同条件下Cu/MgO (TOF=356.7 h^-1)和Pd/MgO (TOF=34.8 h^-1)的2.3倍和23倍。基于实验测试和表征结果,发现CuPd/MgO催化剂中纳米CuPd合金与表面富集缺陷的MgO载体之间存在金属-载体强相互作用。这种相互作用能够促进氧气在催化剂表面吸附活化并生成活性氧物种(超氧阴离子自由基,·O₂^-),·O₂^-先后促进甲醛中的C—H键断裂和水分子的解离,随后与反应体系中生成的质子及氢自由基(·H)依次结合,最终实现氢气的析出与氧气的再生。     

高比表面介孔LaNiO3负载纳米Au催化剂的研究

分别采用纳米铸型法和溶胶-凝胶法制备了系列LaNiO₃载体,并用沉积-沉淀法制备了系列Au/LaNiO₃催化剂.对催化剂进行了XRD、BET、AAS、TEM和XPS等表征,测试了其对CO催化氧化活性.实验结果表明,纳米铸型法得到的LaNiO₃-NCM具有介孔结构,且比表面积可达126 m²·g^-1,以其为载体制备的Au/LaNiO₃-NCM催化剂在30℃条件下将CO完全转化,活性远高于以传统溶胶-凝胶法制备的LaNiO₃-SG为载体的金催化剂.XPS结果表明该Au/LaNiO₃-NCM催化剂表面存在较多的氧化态Au^δ+（0 < δ < 3）和晶格氧,且活性组分Au含量也较高,说明高比表面介孔LaNiO₃载体有利于提高活性组分Au的负载量,从而提高催化剂催化活性.     

高(111)晶面暴露的Pd纳米颗粒的制备与表征及其加氢性能

通过液相氢气还原法,在不同温度下制备出了不同（111）晶面占比的Pd单晶纳米颗粒,用活性炭吸附制备成Pd/C纳米催化剂。通过透射电子显微镜（TEM）、傅里叶变换（FFT）、X射线衍射（XRD）表征证实了低温下制备的Pd纳米颗粒具有较高的（111）晶面占比。氢氧脉冲滴定（H₂-O₂）和H₂-程序升温脱附（H₂-TPD）结果显示,上述催化剂表面吸附氢气量与其Pd（111）晶面占比呈线性关系。此外,该系列Pd/C催化剂具有相似的粒径4.3 nm以及较窄的尺寸分布,相近的孔隙参数和Pd负载量,从而可对比（111）晶面比例差异对其加氢性能的影响。3个探针反应（苯乙烯、环己烯和对硝基甲苯的加氢反应）的实验结果表明,相比于低（111）晶面暴露比例的Pd/C催化剂,含有高（111）晶面暴露比例的Pd/C催化剂显示出更高的加氢活性,且Pd（111）晶面比例与氢气消耗速率呈一定的线性关系,这归因于H₂优先吸附于Pd（111）晶面促进了活性氢原子的形成。基于以上分析,高（111）晶面暴露的Pd基催化剂有利于加氢性能的提高。     

炭载Pd-Fe合金催化剂的制备及电催化氧还原活性

研究了用NH₄Cl作配位剂的配位还原法来制备的Pd-Fe/C催化剂,发现由于NH₄Cl能与Pd形成配合物,使PdCl₂的还原电位负移,与FeCl₃的还原电位接近,从而在低温下制备得到了高合金化程度的Pd-Fe/C催化剂。XPS表征结果表明:Pd与Fe形成合金后,Pd的电荷密度的减少,增加了Pd⁰的含量。因此,得到的Pd-Fe/C催化剂对氧还原的电催化活性比用相同方法制得的Pd/C催化剂高,而且该催化剂对甲醇氧化没有电催化活性。     

Palladium Nanoparticles Embedded into Graphene Nanosheets: Preparation,Characterization, and Nonenzymatic Electrochemical Detection of H2O2

A novel nonenzymatic H₂O₂ sensor based on a palladium nanoparticles/graphene (Pd‐NPs/GN) hybrid nanostructures composite film modified glassy carbon electrode (GCE) was reported. The composites of graphene (GN) decorated with Pd nanoparticles have been prepared by simultaneously reducing graphite oxide (GO) and K₂PdCl₄ in one pot. The Pd‐NPs were intended to enlarge the interplanar spacing of graphene nanosheets and were well dispersed on the surface or completely embedded into few‐layer GN, which maintain their high surface area and prevent GN from aggregating. XPS analysis indicated that the surface Pd atoms are negatively charged, favoring the reduction process of H₂O₂. Moreover, the Pd‐NPs/GN/GCE could remarkably decrease the overpotential and enhance the electron‐transfer rate due to the good contact between Pd‐NPs and GN sheets, and Pd‐NPs have high catalytical effect for H₂O₂ reduction. Amperometric measurements allow observation of the electrochemical reduction of H₂O₂ at 0.5 V (vs. Ag/AgCl). The H₂O₂ reduction current is linear to its concentration in the range from 1×10^?9 to 2×10^?3 M, and the detection limit was found to be 2×10^?10 M (S/N=3). The as‐prepared nonenzymatic H₂O₂ sensor exhibits excellent repeatability, selectivity and long‐term stability.     

掺氮石墨烯-铜基催化剂的制备及催化性能

采用水热法合成掺氮石墨烯(N/GN),通过超声辅助等体积浸渍法制备掺氮石墨烯-铜基催化剂(Cu-N/GN)。通过XRD、SEM、TEM、N2吸附脱附、XPS和XAES对催化剂的微观结构、形貌及元素组成进行表征,并考察Cu-N/GN对乙炔氢氯化反应的催化性能。结果表明:在催化剂中铜颗粒尺寸较小、均匀分布于N/GN片层上,且铜含量较低(3.6%);Cu-N/GN对乙炔氢氯化反应的催化效果良好,乙炔转化率为68%,氯乙烯选择性为99%。     

Germanium Quantum Dots Embedded in N‐Doping Graphene Matrix with Sponge‐Like Architecture for Enhanced Performance in Lithium‐Ion Batteries

Germanium quantum dots embedded in a nitrogen‐doped graphene matrix with a sponge‐like architecture (Ge/GN sponge) are prepared through a simple and scalable synthetic method, involving freeze drying to obtain the Ge(OH)₄/graphene oxide (GO) precursor and subsequent heat reduction treatment. Upon application as an anode for the lithium‐ion battery (LIB), the Ge/GN sponge exhibits a high discharge capacity compared with previously reported N‐doped graphene. The electrode with the as‐synthesized Ge/GN sponge can deliver a capacity of 1258 mAh g^?1 even after 50 charge/discharge cycles. This improved electrochemical performance can be attributed to the pore memory effect and highly conductive N‐doping GN matrix from the unique sponge‐like structure.     

One‐Step Synthesis of β‐Cyclodextrin Functionalized Graphene/Ag Nanocomposite and Its Application in Sensitive Determination of 4‐Nitrophenol

β‐Cyclodextrin functionalized graphene/Ag nanocomposite (β‐CD/GN/Ag) was prepared via a one‐step microwave treatment of a mixture of graphene oxide and AgNO₃. β‐CD/GN/Ag was employed as an enhanced element for the sensitive determination of 4‐nitrophenol. A wide linear response to 4‐nitrophenol in the concentration ranges of 1.0×10^?8–1.0×10^?7 mol/L, and 1.0×10^?7–1.5×10^?3 mol/L was achieved, with a low detection limit of 8.9×10^?10 mol/L (S/N=3). The mechanism and the heterogeneous electron transfer kinetics of the 4‐nitrophenol reduction were discussed according to the rotating disk electrode experiments. Furthermore, the sensing platform has been applied to the determination of 4‐nitrophenol in real samples.     

Simple and rapid synthesis of ternary polyaniline/titanium oxide/graphene by simultaneous TiO<Subscript>2</Subscript> generation and aniline oxidation as hybrid materials for supercapacitor applications

This paper reports a simple methodology for the synthesis of a polyaniline/titanium oxide/graphene hybrid (Pani/TiO₂/GN) using a simple methodology, and their application as a supercapacitor electrode material for energy storage. The Pani/TiO₂/GN hybrid was prepared by a simple approach by simultaneous generation of Pani and TiO₂ in situ from aniline and titanium iso-propoxide, respectively, in the presence of GN under ice bath conditions. The incorporation of GN improved the electrical conductivity of Pani and helped to decrease the charge transfer resistance, whereas TiO₂ generation by an in situ method increased the surface area considerably and enhanced the capacitance of the Pani/TiO₂/GN hybrid. TEM showed that Pani and TiO₂ were well incorporated and coated on the GN successfully. The shift of the peaks in the FTIR spectrum and XRD pattern of the Pani/TiO₂/GN hybrid compared to their pure counterparts suggested that TiO₂ and Pani had been perfectly coated on the GN, and there was a strong interaction among Pani, GN, and TiO₂ particles. The electrochemical performance of the as-prepared Pani/TiO₂/GN hybrid electrode showed a high specific capacitance of 403.2 F g^?1 at a current density of 2 A g^?1 and excellent cycling stability for up to 1000 cycles. This suggested that the effective incorporation of GN and TiO₂ into Pani and the high surface area could simultaneously increase the electrochemical capacitance and cyclic stability of the Pani/TiO₂/GN hybrid, leading to superior electrochemical performance.

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Graphical abstract The electrochemical performance of as-prepared Pani/TiO₂/GN hybrid electrode showed a high specific capacitance of 403.2 F g^?-1 at a current density of 2 A g^?-1 and excellent cycling stability for up to 1000 cycles. This suggested that the effective incorporation of GN and TiO₂ into Pani and the high surface area could simultaneously increase the electrochemical capacitance and cycle stability of the Pani/TiO₂/GN hybrid, leading to superior electrochemical performance.

     

An Efficient RuTe2/Graphene Catalyst for Electrochemical Hydrogen Evolution Reaction in Acid Electrolyte

Developing efficient powder catalysts for hydrogen evolution reaction (HER) in the acidic electrolyte is significant for hydrogen generation in the proton exchange membrane (PEM) water electrolysis technique. Herein, we demonstrated an efficient catalyst for HER in the acid media based on the graphene supported ruthenium telluride nanoparticles (RuTe₂/Gr). The catalysts were easily fabricated by a facile microwave irradiation/thermal annealing approach, and orthorhombic RuTe₂ crystals were found anchored over the graphene surface. The defective structure was demonstrated in the aberration‐corrected transmission electron microscopy images for RuTe₂ crystals and graphene support. This catalyst required an overpotential of 72 mV to drive 10 mA cm^?2 for HER when loading on the inert glass carbon electrode; Excellent catalytic stability in acidic media was also observed to offer 10 mA cm^?2 for 10 hours. The Volmer‐Tafel mechanism was indicated on RuTe₂/Gr catalyst by Tafel slope of 33 mV dec^?1, similar to that of Pt/C catalysts. The high catalytic performance of RuTe₂/Gr could be attributed to its high dispersion on the graphene surface, high electrical conductivity and low charge transfer resistance. This powder catalyst has potential application in the PEM water electrolysis technique because of its low cost and high stability.     

Heterogenized peroxopolyoxotungstate catalyst on the surface of clicked magnetite‐graphene oxide nanocomposite: Magnetically recoverable epoxidation catalyst

A new heterogeneous catalyst for the epoxidation of olefins was prepared by immobilization of peroxophosphotungstate anions on the surface of clicked magnetite‐graphene oxide as magnetically recoverable support. To prepare the heterogeneous catalyst, the clicked magnetite‐graphene oxide support was prepared by thiolene click reaction of thiol functionalized graphene oxide with vinyl modified magnetite nanoparticles. The tailored support was then modified with aminopropyl groups followed by electrostatic interaction with peroxophosphotungstate anions to achieve the desired heterogeneous catalyst. Characterization of the catalyst was performed by various physicochemical methods which confirmed the successful immobilization of peroxopolyoxotungstate species on the surface of clicked magnetite‐graphene oxide. Catalytic activity of the catalyst revealed its high catalytic activity and selectivity in the epoxidation of various olefins in the presence of H₂O₂ as green oxidant. This heterogeneous catalyst can be magnetically reused several times without significant loss of activity and selectivity.     

Influence of borohydride concentration on the synthesized Au/graphene nanocomposites for direct borohydride fuel cell

Au/graphene nanocomposites are prepared via a one-pot chemical reduction process at room temperature, using graphene oxide (GO) and chloroauric acid (HAuCl₄) as precursors. The obtained Au/graphene nanocomposites are characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). TEM shows that the Au nanoparticles with size of approximately 8.7 nm disperse randomly on the surface of graphene. XPS confirms that the Au/graphene nanocomposites show a higher atomic percentage of C/O (6.3/1), in contrast to its precursor GO (2.2/1). Electrochemical studies reveal that the Au/graphene nanocomposites have electrochemically active surface area of 9.82 m² g^?1. Besides, the influence of borohydride concentration on the as-prepared Au/graphene nanocomposites is investigated in details by cyclic voltammetry, chronoamperometry, and chronopotentiometry. The results indicate that high concentration of borohydride can significantly improve the electrochemical performance of the Au/graphene catalyst.     

Ultrasensitive electrochemical immunoassay for carcinoembryonic antigen based on three-dimensional macroporous gold nanoparticles/graphene composite platform and multienzyme functionalized nanoporous silver label

Three-dimensional macroporous gold nanoparticles/graphene composites (3D-AuNPs/GN) were synthesized through a simple two-step process, and were used to modify working electrode sensing platform, based on which a facile electrochemical immunoassay for sensitive detection of carcinoembryonic antigen (CEA) in human serum was developed. In the proposed 3D-AuNPs/GN, AuNPs were distributed not just on the surface, but also on the inside of graphene. And this distribution property increased the area of sensing surface, resulting in capturing more primary antibodies as well as improving the electronic transmission rate. In the presence of CEA, a sandwich-type immune composite was formed on the sensing platform, and the horseradish peroxidase-labeled anti-CEA antibody (HRP-Ab₂)/thionine/nanoporous silver (HRP-Ab₂/TH/NPS) signal label was captured. Under optimal conditions, the electrochemical immunosensor exhibited excellent analytical performance: the detection range of CEA is from 0.001 to 10 ng mL⁻¹ with low detection limit of 0.35 pg mL⁻¹ and low limit of quantitation (LOQ) of 0.85 pg mL⁻¹. The electrochemical immunosensor showed good precision, acceptable stability and reproducibility, and could be used for the detection of CEA in real samples. The proposed method provides a promising platform of clinical immunoassay for other biomolecules