碳载PtSn催化剂上乙醇电氧化的原位时间分辨红外光谱研究

采用调变的多元醇法制备了高分散碳载PtSn催化剂(PtSn/C),XRD测试结果表明金属粒子的平均粒径为2.2 nm,略小于Pt/C催化剂,而晶格参数相对增大。通过电化学原位时间分辨红外光谱研究了乙醇在PtSn/C催化剂上的吸附和氧化过程,表明线性吸附态CO(CO_L)是主要的乙醇解离吸附物种,导致催化剂中毒,阻止反应继续进行;当电位增大到0.3 V时,出现了乙醛和乙酸的红外吸收峰,作为乙醇解离吸附的竞争反应,乙醛和乙酸的生成有效抑制了催化剂中毒,随着电位的增大和时间的延长,生成乙酸的选择性增大;电位进一步增大至0.4 V时有微弱CO₂吸收峰出现,是乙醇电氧化的最终产物,主要来自于CO_L的氧化消耗。根据实验结果讨论了PtSn/C催化剂上乙醇的电催化氧化机理。     

PtRhSn/GN催化剂上甲醇电催化氧化的原位红外光谱研究

通过多元醇还原法制备了石墨烯(GN)负载的Pt及Pt基多元催化剂:Pt/GN,PtRh/GN,PtSn/GN,PtRhSn/GN。循环伏安研究表明,Rh的加入提升了Pt基催化剂的甲醇电催化氧化活性,而Sn的加入明显降低了甲醇在Pt基催化剂上的过电位,起始氧化电位负移106mV。电化学原位红外光谱研究进一步表明,Rh和Sn的加入使得Pt基催化剂对甲醇氧化的起始氧化电位负移;Rh的加入使得CO谱峰强度增大,而Sn的加入明显降低了CO谱峰强度。三元催化剂PtRhSn/GN很好的综合了Rh和Sn的电子效应及协同效应特点,相比于Pt/GN催化剂,起始氧化电位负移60mV,且活性达到其1.57倍。     

Pt/C催化剂中纳米Pt颗粒团聚效应的小角X射线散射

 应用小角X射线散射(SAXS)技术,对乙二醇合成法、浸渍还原法和微波加热法制备的Pt/C催化剂粉体内纳米Pt颗粒的团聚效应进行了研究,得到了不同方法制备的Pt颗粒及其团聚体的特征尺寸、体积分布、表面积变化、团聚程度等信息,并利用透射电镜（TEM）对3种样品进行了测试。实验结果表明:微波加热法制备的催化剂中,Pt颗粒较好地分散于C载体上,且Pt颗粒具有尺度小、分布范围窄、总表面积大和团聚体较少等特征;常规浸渍和乙二醇还原两种方法制备的催化剂中Pt颗粒大小分布相似,但乙二醇还原法制备的催化剂总表面积和团聚体尺度更大,数量也更多。     

无表面活性剂Pt和PtRu纳米粒子制备及其甲醇氧化活性

利用一种简单的方法制备不含任何表面活性剂并具有高甲醇氧化活性的Pt和PtRu纳米电催化剂. 以CO为还原剂, CO和多壁碳纳米管(MWCNT_s)为保护剂和载体,通过一步反应得到沉积在多壁碳纳米管上Pt纳米粒子,在制备过程中无需使用任何有机溶剂或表面活性剂. 利用循环伏安法和计时电流法表征了所合成催化剂的甲醇氧化活性,甲醇氧化的峰电位(ca. 0.9 V vs. RHE)处的电流密度和比质量电流高达11.6 mA/cm² 和860 mA/mg_Pt. 在Pt/MWCNT_s表面电沉积Ru后,催化剂在低电位处的甲醇氧化活性得到提高,其在0.5和0.6 V的稳态比质量电流分别达到了20和80 mA/mg.     

氯柱硼镁石在硼酸溶液中溶解转化的Raman光谱

利用Raman光谱对氯柱硼镁石在30 ℃时,4.5%的硼酸水溶液中溶解相转化过程进行了研究。研究结果表明相转化产物为库水硼镁石(2MgO·3B₂O₃·15H₂O)。根据Raman光谱位移对溶液中各种聚硼酸根B(OH)-₄,B₂O(OH)2-₆,B₃O₃(OH)-₄等阴离子的Raman峰进行了归属以及它们间的相互作用分别进行了讨论分析。提出了溶液中硼氧配阴离子的存在形式及其相互作用机理和我国青藏高原盐湖区库水硼镁石形成的地球化学成盐条件和机理。     

表面合金电催化剂上甲酸氧化的原位FTIR反射光谱研究

运用原位红外反射光谱(FTIRS)和电化学循环伏安法(CV)研究了甲酸在三种不同电极上的电催化特性。结果表明甲酸在碳载铂电极(Pt/GC)上的电催化氧化机理与本体铂电极(Pt)相类似,即可以通过活性中间体或毒性中间体氧化至CO_2。Pt/GC对甲酸的氧化比Pt具有更高的电催化活性。Pt/GC表面以Sb吸附原子修饰的电极(Sb-Pt/GC)上,甲酸氧化的起始电位(E;)提前至-0.10V,氧化电流峰电位(Ep)提前至0.34V,氧化峰电流(jp)值增加了7.28倍,半峰宽(FWHM)为0.30V。同样,Surface al-loy/GC电极上,E_I为-0.12V,E_p为0.32V和j_p为7.25mA·cm~(-2),相对Pt/GC分别负移了0.22,0.02V和增大了8.15倍,半峰宽(FWHM)为0.5V。表明Sb-Pt/GC和Surface alloy/GC电极不仅能够有效地抑制毒性中间体CO的生成,而且还可以显著地提高其对活性中间体的氧化的电催化活性。     

有机硼酸盐插层Zn/Al-LDH的红外和拉曼光谱特征

研究了碳酸根和硼酸根的二元锌铝水滑石的X射线衍射,拉曼和红外光谱特征。采用一步水热共沉淀法,分别制得结晶良好的层间为碳酸根和硼酸根的二元锌铝水滑石。X射线衍射分析显示,硼酸根插层后水滑石（003）特征衍射峰向小角度移动,峰型尖锐,水滑石通道高度从0.28 nm增加至0.42 nm;红外光谱和拉曼光谱特征表明,硼酸根插层后,碳酸根的红外和拉曼特征峰消失。层间硼酸根以B₃O₃(OH)-₄,B₄O₅(OH)2-₄和B(OH)-₄三种形式存在。随层间离子的不同,与羟基相关的红外光谱和拉曼光谱峰位均有所改变。研究结果表明以硼酸三正丁酯为插层剂,可获得单一相、纯度较高的硼酸根型锌铝水滑石,拉曼光谱可准确探测水滑石层间阴离子变化对其结构和性能的影响。     

Pt/TiO2催化剂的载体结构对甲醇催化氧化性能的影响

二氧化钛载体包括二氧化钛纳米管阵列(TNTAs)和二氧化钛纳米线阵列(TNWAs)两种,载体的结构不同对催化性能有一定的影响。然而,Pt负载在TNTAs和TNWAs催化性能的比较鲜有报道。本文通过微波法制备了Pt/TNTAs和Pt/TNWAs两种催化剂,结果表明,Pt/TNTAs催化甲醇氧化效果要优于Pt/TNWAs。相较于Pt/TNWAs, Pt/TNTAs的优越催化性能可能与纳米管的限域效应有关。可见,载体的结构对催化剂的性能有很大的影响。     

Pt/TiO_2催化剂的载体结构对甲醇催化氧化性能的影响（英文）

二氧化钛载体包括二氧化钛纳米管阵列(TNTAs)和二氧化钛纳米线阵列(TNWAs)两种,载体的结构不同对催化性能有一定的影响.然而,Pt负载在TNTAs和TNWAs催化性能的比较鲜有报道.本文通过微波法制备了Pt/TNTAs和Pt/TNWAs两种催化剂,结果表明,Pt/TNTAs催化甲醇氧化效果要优于Pt/TNWAs.相较于Pt/TNWAs,Pt/TNTAs的优越催化性能可能与纳米管的限域效应有关.可见,载体的结构对催化剂的性能有很大的影响.     

水溶液中硫酸根离子的拉曼光谱定量分析

拉曼光谱因其具有无损、非接触以及原位的技术优势被广泛应用于科学研究领域。但是,当前拉曼光谱主要应用于定性研究,即根据拉曼波数偏移进行物质分子的鉴别,相比之下,拉曼光谱定量分析则明显不足。因此,有必要进一步开展拉曼光谱定量方面的研究。根据拉曼光谱原理分析可知,拉曼光谱定量研究应当根据相对强度比进行,也就是在定量化过程中需要选择一个参考系,可以分为内标法和外标法。拉曼光谱定量可以根据被测分子与该参考系的拉曼强度比值进行,通过这个方法可以消除测试条件的影响。对水溶液而言,可将液态水的OH伸缩振动作为内标,进行拉曼光谱定量分析。本文研究了Na₂SO₄-H₂O,K₂SO₄-H₂O以及NaCl-Na₂SO₄-H₂O体系的拉曼光谱特征。通过将水分子的OH伸缩振动（2 750~3 900 cm-1附近）拟合为两个高斯谱峰,并以I_SO2-4/I_W为参数来确定溶液中的硫酸根离子浓度,其中I_SO2-4为硫酸根离子的特征峰强度,I_W为水的两个高斯谱峰强度之和。实验结果表明,水溶液中SO2-₄浓度与拉曼强度比I_SO2-4/I_W之间有较好的线性关系,其中,R2=0.997 73,符合定量要求。据此,本文应用拉曼光谱定量分析,建立了一种相对快速、准确测量水溶液中SO2-₄浓度的方法。     

Electrooxidation of ethanol using Pt rare earth–C electrocatalysts prepared by an alcohol reduction process

Pt rare earth–C electrocatalysts (rare earth = La, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm, and Lu) were prepared by an alcohol reduction process using ethylene glycol as reduction agent and solvent and Vulcan XC 72 as support. The electrocatalysts were characterized by energy-dispersive X-ray analysis, X-ray diffraction (XRD), and cyclic voltammetry. The electrooxidation of ethanol was studied in acid medium by cyclic voltammetry and chronoamperometry using thin porous coating technique. The XRD patterns indicate that all electrocatalysts present the face-centered cubic structure of Pt and the presence of rare earth hydroxides. All electrocatalysts prepared by this methodology showed superior performance for ethanol electrooxidation at room temperature compared to Pt–C.     

Synthesis of Pt-Ni-Fe/CNT/CP nanocomposite as an electrocatalytic electrode for PEM fuel cell cathode

In order to use carbon nanotube (CNT)-supported catalyst as fuel cell electrodes, Pt-Ni-Fe/CNT/carbon paper (CP) electrode was prepared using an ethylene glycol reduction method. CNTs were directly synthesized on Ni-impregnated carbon paper, plain carbon cloth, and Teflonized carbon cloth using chemical vapor deposition. FESEM and TEM images and thermogravimetric analysis indicated that in situ CNT on carbon paper (ICNT/CP) possesses more appropriate structural quality and stronger adhesion to the substrate than other substrates. The contact angle analysis demonstrated that the degree of ICNT/CP surface hydrophobicity encountered a 24% increase in comparison to CP and promoted to superhydrophobicity from hydrophobicity. The polarization curves and electrochemical impedance spectroscopy results of the loaded Pt-Ni-Fe on in situ and ex situ CNT/CP illustrated that the power density increased and charge transfer resistance reduced compared to commercial Pt/C loaded on CP. The results can be attributed to the outstanding properties of CNTs and high catalytic activity of triple catalysts causing alloying of Pt with Ni and Fe, which makes them a proper candidate to be used as cathode electrodes in proton exchange membrane fuel cells.     

Electro-oxidation of ethylene glycol on PtSn/C and PtSnNi/C electrocatalysts

A PtSn/C electrocatalyst with a Pt–Sn molar ratio of 50:50 and A PtSnNi/C electrocatalyst with a Pt–Sn–Ni molar ratio of 50:40:10 were prepared by alcohol-reduction process using ethylene glycol as solvent and reducing agent. The electrocatalysts were characterized by energy dispersive X-ray, X-ray diffraction, and cyclic voltammetry. The electro-oxidation of ethylene glycol was studied by cyclic voltammetry and chronoamperometry using the thin porous coating technique. PtSnNi/C electrocatalyst showed a superior performance compared to PtSn/C electrocatalysts in the potential range of interest for a direct ethylene glycol fuel cell.     

Preparation of PtSnSb/C by an alcohol reduction process for direct ethanol fuel cell (DEFC)

PtSn/C and PtSnSb/C electrocatalysts (20 wt.% metal loading) were prepared by an alcohol reduction process using H₂PtCl₆.6H₂O, SnCl₂.2H₂O, and Sb(OOCCH3) as metal sources, ethylene glycol as solvent and reducing agent, and Vulcan XC72 as carbon support. The electrocatalysts were characterized by energy dispersive X-ray analysis, X-ray diffraction, and transmission electron microscopy, while that the performance for ethanol oxidation was investigated by cyclic voltammetry and chronoamperommetry (chrono) at room temperature. The diffractograms of the PtSn/C and PtSnSb/C electrocatalysts showed four peaks associated to Pt face-centered cubic structure and two peaks that were related to a SnO₂ phase. For PtSb/C and PtSnSb/C electrocatalysts, no Sb (antimony) peaks corresponding to a metallic antimony or antimony oxide phases were observed. Transmission electron microscopy images showed that the metal particles were homogeneously distributed over the support. The PtSnSb/C (50:45:05) electrocatalyst showed an increase of performance for ethanol oxidation in relation to PtSn/C electrocatalyst at room temperature. In the tests at 100 °C on a single cell of a direct ethanol fuel cell, the maximum power density of PtSnSb/C (50:45:05) electrocatalyst was slightly higher than that of PtSn/C electrocatalyst.     

Ethylene glycol reflux synthesis of carbon nanotube/ceria core-shell nanowires

Carbon nanotube (CNT)/ceria core-shell nanowires were prepared facilely on a large scale under the boiling reflux of ethylene glycol. The composites are characterized by transmission electron microscopy, X-ray diffraction as well as Fourier transformed infrared spectra. It is found that the entire outer surface of CNTs is fully sheathed with a dense layer of uniform nanosized CeO₂, and that the thickness of the coating sheath can be readily manipulated by tuning the molar ratio of ceria to CNTs. Finally, a possible formation mechanism has been suggested as follows: with the high reaction temperature, ethylene glycol is partially converted to oxalic acid, and the surface hydroxyl groups of CeO₂ tiny particles react with oxalic acid to form the polymer-like inorganic-organic compounds. Subsequently, in view of the low-energy point, the polymer-like inorganic-organic compounds are coated on the surface of CNTs, and thus CNTs/ceria core-shell composites are obtained.     

Electro-oxidation of ethanol using PtSnRh/C electrocatalysts prepared by an alcohol-reduction process

PtRh/C (90:10), PtRh/C (50:50), PtSn/C (50:50), and PtSnRh/C (50:40:10) electrocatalysts were prepared by an alcohol-reduction process using ethylene glycol as solvent and reduction agent and Vulcan Carbon XC72 as supports. The electrocatalysts were characterized by energy-dispersive X-ray analysis, X-ray diffraction, and transmission electron microscopy. The electro-oxidation of ethanol was studied by cyclic voltammetry chronoamperometry at room temperature and on a single cell of a direct ethanol fuel cell at 100 °C. Cyclic voltammetry and chronoamperometry experiments showed that PtSnRh/C and PtSn/C electrocatalysts have similar performance for ethanol oxidation at room temperature, while the activity of PtRh/C electrocatalysts was very low. At 100 °C on a single cell, PtSnRh/C showed superior performance compared to PtSn/C and PtRh/C electrocatalysts.     

A comparative study for the electrocatalytic oxidation of alcohol on Pt-Au nanoparticle-supported copolymer-grafted graphene oxide composite for fuel cell application

The platinum-gold bimetallic nanoparticles supported poly(cyclotriphosphazene-co-benzidine)-grafted graphene oxide (poly(CP-co-BZ)-g-GO) composite has been prepared for electrochemical performance studies. Cyclic voltammetry and chronoamperometric studies were carried out to check the electrochemical properties of Pt-Au/poly(CP-co-BZ)-g-GO and Pt/poly(CP-co-BZ)-g-GO catalysts for methanol, ethylene glycol and glycerol in alkaline medium. The morphology and crystalline structure of the prepared Pt-Au/poly(CP-co-BZ)-g-GO and Pt/poly(CP-co-BZ)-g-GO and catalysts have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FT-IR). From the electrochemical results, it was concluded that Pt-Au/poly(CP-co-BZ)-g-GO catalyst shows higher catalytic activity and stability compared to Pt/poly(CP-co-BZ)-g-GO catalyst. The catalytic activity of Pt/poly(CP-co-BZ)-g-GO catalyst has been compared with Pt/poly(CP-co-BZ), Pt/GO and Pt/C catalysts. In addition, oxidation current of ethylene glycol is higher than the methanol and glycerol in alkaline medium on the prepared catalyst.     

Effect of Ni proportion on the performance of proton exchange membrane fuel cells using PtNi/C electrocatalysts

PtNi/C electrocatalysts were synthesised by borohydride method on functionalised carbon support. Energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy and both cyclic and linear voltammetry were employed to characterise the composition, crystalline structure, morphology and catalytic properties of the PtNi/C electrocatalysts. Different Ni proportions in the PtNi/C electrocatalysts were evaluated in the cathode or anode in a H₂/air proton exchange membrane fuel cells (PEMFC) by polarisation curves. PtNi particles uniformly dispersed with different proportions of metals obtained. The increase of Ni proportion in the electrocatalyst led to materials with higher mass activity values toward the oxygen reduction reaction and a greater electrochemical-active surface area. PtNi/C electrocatalysts in the cathode presented higher mass activity values at high potential in the PEMFC. The best PEMFC performance was obtained with PtNi 13 at.% Ni (cathode) and Pt/C (anode) relative to the Pt/C (cathode and anode) with identical Pt loadings. PtNi/C electrocatalysts in PEMFC may be used as an alternative to Pt/C electrocatalyst.     

Preparation and characterization of PtRu/C-rare earth using an alcohol-reduction process for ethanol electro-oxidation

PtRu/C (100% C) and PtRu/C-CeO₂, PtRu/C-La₂O₃, PtRu/C-Nd₂O₃, and PtRu/C-Er₂O₃ (85% C and 15% rare earth) electrocatalysts were prepared in a single step by an alcohol-reduction process using H₂PtCl₆ 6H₂O and RuCl₃ xH₂O as metal sources, ethylene glycol as solvent and reducing agent, Vulcan XC72 and rare earth (RE) as support. The electrocatalysts were characterized by energy dispersive X-ray, X-ray diffraction, and transmission electron microscopy. The performance for ethanol oxidation was investigated by cyclic voltammetry and chronoamperommetry at room temperature, and studies on the direct ethanol fuel cell were carried at 100 °C. The Pt:Ru atomic ratios were similar to the nominal used in preparation, and the average particle sizes were in the range of 2.0–3.0 nm. All PtRu/C-RE electrocatalysts showed an increase of performance for ethanol oxidation at room temperature and also on a single direct ethanol fuel cell tests in relation to PtRu/C electrocatalyst at 100 °C.     

Preparation of PtSn/C electrocatalysts using citric acid as reducing agent for direct ethanol fuel cell (DEFC)

PtSn/C electrocatalysts (Pt:Sn atomic ratios of 50:50 and 60:40) were prepared using citric acid as reducing agent, and the pH of the reaction medium was varied by the addition of OH⁻ ions. The obtained electrocatalysts were characterized by energy dispersive X-ray analysis, X-ray diffraction, and transmission electron microscopy. The electrocatalysts were tested on the direct ethanol fuel cell (DEFC) at 90 °C. The obtained PtSn/C electrocatalysts showed the presence of a face-centered cubic, Pt, and SnO₂ phases. In DEFC studies, the PtSn/C electrocatalysts showed a superior performance compared to a commercial PtSn/C and Pt/C electrocatalysts from E-TEK.