PtRu/C电催化剂上甲醇吸附氧化过程的电化学原位红外光谱

采用调变的多元醇法制备了高分散的Pt/C, PtRu/C和Ru/C电催化剂. XRD计算结果表明, PtRu/C电催化剂的平均粒径和合金度分别为2.2 nm和71%. 采用电化学方法和原位傅里叶变换红外反射光谱方法(in situ FTIRS)研究了甲醇在3种电催化剂上的吸附氧化过程, 发现PtRu/C对甲醇的催化活性明显高于Pt/C, Ru的加入一方面影响了甲醇在Pt上的解离吸附性能, 另一方面提供了Ru-OH物种, 从而抑制了低电位下电催化剂中毒. 红外光谱研究结果表明, 线性吸附态CO(COL)是主要毒化物种, 反应产物主要是CO2, 还有少量的甲酸甲酯. 根据实验结果讨论了甲醇在PtRu/C电催化剂上的氧化机理.     

中空树枝状三氧化钨载铂催化剂对甲醇的电催化氧化性能研究

采用水热法和牺牲模板法相结合制备具有中空树枝结构的三氧化钨载体(d-WO₃),在其表面进一步负载活性成分Pt,得到纳米Pt/d-WO₃复合催化剂。采用X射线粉末衍射(XRD)、透射电镜(TEM)和比表面积和孔结构分析(BET)等对催化剂的形貌和结构进行了表征。结果表明,三氧化钨具有长6 μm和宽2 μm的中空树枝状结构,孔径分布主要集中在20~120 nm,比表面积为24 m²/g,平均粒径为7.2 nm的Pt纳米粒子均匀分布在其表面。采用循环伏安和计时电流法研究了Pt/d-WO₃催化剂在酸性溶液中对甲醇的电催化氧化性能。结果表明,Pt/d-WO₃催化剂比Pt/C和Pt/WO₃催化剂对甲醇有更高的电催化氧化活性和稳定性。d-WO₃所具有的中空介孔结构和双功能作用机理有利于甲醇在铂表面的直接脱氢氧化过程。     

Metal Oxide Promoted Electrocatalysts for Methanol Oxidation

An important research target in DMFCs is to find better catalyst materials that are cheaper, less-prone to poisoning and more catalytically active. In this context, metal oxides with good catalytic properties and stronger interaction with Pt nanoparticles can generate active interfacial regions for electrocatalysis. Pt catalysts promoted by certain metal oxides show enhanced methanol electro-oxidation activity and CO tolerance behavior. In this paper we summarize the recent progress from our laboratory which explored the possibility of developing Pt–MoO₃/C and Pt–Nb₂O₅/C electrocatalysts in acidic media, and Pt–V₂O₅/C electrocatalyst in alkaline media for direct electro-oxidation of methanol. The oxide electrocatalysts have been prepared by a fast and efficient method of loading the metal oxide on carbon black (Vulcan XC-72) employing an intermittent microwave heating (IMH) method. These materials are found to achieve higher activity and stability towards methanol electro-oxidation.     

Methanol oxidation in acidic and alkaline electrolytes using PtRuIn/C electrocatalysts prepared by borohydride reduction process

PtRuIn/C electrocatalysts( 20% metal loading by weight) were prepared by sodium borohydride reduction process using H_2PtCl6·6H_2O,RuCl_3·xH_2O and InCl_3·xH_2O as metal sources,borohydride as reducing agent and Carbon Vulcan XC72 as support. The synthetized PtRuIn/C electrocatalysts were characterized by X-ray diffraction( XRD),energy dispersive analysis( EDX),transmission electron microscopy( TEM),cyclic voltammetry( CV),chronoamperommetry( CA) and polarization curves in alkaline and acidic electrolytes( single cell experiments). The XRD patterns showPtpeaks are attributed to the face-centered cubic( fcc) structure,and a shift of Pt( fcc) peaks indicates that Ru or In is incorporated into Ptlattice. TEMmicrographs showmetal nanoparticles with an average nanoparticle size between 2.7 and 3.5 nm. Methanol oxidation in acidic and alkaline electrolytes was investigated at room temperature,by CV and CA. PtRu/C( 50 ∶ 50) shows the highest activity among all electrocatalysts in study considering methanol oxidation for acidic and alkaline electrolyte. Polarization curves at 80 ℃ showPtRuIn/C( 50 ∶ 25 ∶ 25)with superior performance for methanol oxidation,when compared to Pt/C,PtIn/C and PtRu/C for both electrolytes. The best performance obtained by PtRuIn/C( 50 ∶ 25 ∶ 25) in real conditions could be associated with the increased kinetics reaction and/or with the occurrence simultaneously of the bifunctional mechanism and electronic effect resulting from the presence of Ptalloy.     

Implanting Atomic Dispersed Ru in PtNi Colloidal Nanocrystal Clusters for Efficient Catalytic Performance in Electro-oxidation of Liquid Fuels

Although PtRu alloy nanocatalysts have been certified to possess excellent electrocatalytic performance and CO-poisoning tolerance toward formic acid and methanol electro-oxidation, the unaffordable usages of ruthenium (Ru) and platinum (Pt) have greatly limited their widespread adoption. Here, a facile one-pot method is reported for implanting atomic dispersed Ru in PtNi colloidal nanocrystal clusters with different Ru/Pt/Ni molar ratios, greatly reducing the dosages of Pt and Ru, and further improving the catalytic performances for the electro-oxidation of formic acid and methanol. Through simple control of the amount of Ni(acac)₂ precursor, trimetallic Ru_0.3Pt_70.5Ni_29.2, Ru_0.6Pt_55.9Ni_43.5, Ru_0.2Pt_77.3Ni_22.5, and Ru_0.9Pt_27.3Ni_71.8 colloidal nanocrystal clusters (CNCs) are obtained. In particular, the Ru_0.3Pt_70.5Ni_29.2 CNCs exhibit excellent specific activities for formic acid and methanol electro-oxidation, that is, 14.2 and 15.3 times higher, respectively, than those of the Pt/C catalyst. Moreover, the Ru_0.3Pt_70.5Ni_29.2 CNCs also possess better anti-CO-poisoning properties and diffusion ability than the other RuPtNi CNCs. The excellent formic acid and methanol electro-oxidation activities of RuPtNi CNCs are ascribed to the optimal ligand effects derived from the Pt, Ni, and atomic dispersed Ru atoms, which can improve the OH adsorption ability and further the anti-CO-poisoning capability. This research opens a new door for increasing the electro-oxidation properties of liquid fuels by using lower dosages of noble metals in Pt-based catalysts.     

Highly active PtRuFe/C catalyst for methanol electro-oxidation

High methanol electro-oxidation activity was obtained on novel PtRuFe/C (2:1:1 at.%) catalyst. Mass and specific activities were 5.67 A  g⁻¹ catal. and 177 mA m⁻² for the PtRuFe/C catalyst while those of the commercial PtRu/C catalyst were 2.28 A g⁻¹ catal. and 87.7 mA m⁻², respectively. CO stripping results showed that on-set voltage for CO electro-oxidation was lowered by incorporation of Fe. XRD and XPS results revealed that Fe₂O₃ was formed instead of Fe(0), which resulted in large electron deficiency in Pt and easy CO electro-oxidation. The electron deficiency of Pt was proved by XPS results of Pt4f peaks, which moved to higher binding energies in PtRuFe/C than PtRu/C.     

Influence of Metal Oxides on Platinum Activity towards Methanol Oxidation in H2SO4 solution

Pt–CeO₂/C, Pt–TiO₂/C, and Pt–ZrO₂/C electrocatalysts were prepared by using a modified microwave‐assisted polyol process. Physical characterization was performed by using XRD, TEM, and EDX analyses. The incorporation of different metal oxides increased the dispersion degree of Pt nanoparticles and reduced their diameter to 2.50 and 2.33 nm when TiO₂ and ZrO₂ were introduced to Pt/C, respectively. The electrocatalytic activity of various electrocatalysts was examined towards methanol oxidation in H₂SO₄ solution by using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Among the studied composites, Pt–ZrO₂/C was selected to be a candidate electrocatalyst for better electrochemical performance in direct methanol fuel cells.     

甲醇电氧化催化剂Pt/CeO2-CNTs与PtRu/C的比较研究

为认识合成催化剂Pt/CeO2-CNTs与商用催化剂PtRu/C(E-TEK)的催化性能和结构特点, 用CO溶出法和恒电位氧化法比较了这两种催化剂对CO的电氧化活性, 运用循环伏安法和恒电位氧化法比较了这两种催化剂对甲醇的电氧化活性. CO电氧化实验结果表明, PtRu/C上CO的电氧化活性明显优于Pt/CeO2-CNTs; 甲醇电氧化实验结果却表明, Pt/CeO2-CNTs与PtRu/C上甲醇电氧化表观活性相当. 为从结构特点上解释PtRu/C上CO电氧化和甲醇电氧化活性的不一致, 对PtRu/C进行了循环伏安扫描和CO溶出实验. 结果表明, PtRu/C的甲醇电氧化电流之所以没有预期高, 一是由于Pt比表面积不够大, 同时Pt-Ru之间协同作用有待提高. 本研究结果表明, 尽管Ru对Pt上CO电氧化有显著助催化作用, 但要充分发挥其对Pt上甲醇电氧化的助催化作用, 需同时提高Pt表面积和Pt-Ru接触界面. 该结论对设计甲醇电氧化催化剂具有普适意义.     

Synthesis of Pt and Pt-Fe nanoparticles supported on MWCNTs used as electrocatalysts in the methanol oxidation reaction

This work reports a feasible synthesis of highly-dispersed Pt and Pt-Fe nanoparticles supported on multiwall carbon nanotubes (MWCNTs) without Fe and multiwall carbon nanotubes with iron (MWCNTs-Fe) which applied as electrocatalysts for methanol electrooxidation. A Pt coordination complex salt was synthesized in an aqueous solution and it was used as precursor to prepare Pt/MWCNTs, Pt/MWCNTs-Fe, and Pt-Fe/MWCNTs using FeCl₂·4NH₂O as iron source which were named S1, S2 and S3, respectively. The coordination complex of platinum (TOA)₂PtCl₆ was obtained by the chemical reaction between (NH₄)₂PtCl₆ with tetraoctylammonium bromide (TOAB) and it was characterized by FT-IR and TGA. The materials were characterized by Raman spectroscopy, SEM, EDS, XRD, TEM and TGA. The electrocatalytic activity of Pt-based supported on MWCNTs in the methanol oxidation was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). Pt-Fe/MWCNTs electrocatalysts showed the highest electrocatalytic activity and stability among the tested electrocatalysts due to that the addition of ”Fe” promotes the OH species adsorption on the electrocatalyst surface at low potentials, thus, enhancing the activity toward the methanol oxidation reaction (MOR).     

Relating the Composition of PtxRu100−x/C Nanoparticles to Their Structural Aspects and Electrocatalytic Activities in the Methanol Oxidation Reaction

A controlled composition‐based method—that is, the microwave‐assisted ethylene glycol (MEG) method—was successfully developed to prepare bimetallic Pt_xRu_100?x/C nanoparticles (NPs) with different alloy compositions. This study highlights the impact of the variation in alloy composition of Pt_xRu_100?x/C NPs on their alloying extent (structure) and subsequently their catalytic activity towards the methanol oxidation reaction (MOR). The alloying extent of these Pt_xRu_100?x/C NPs has a strong influence on their Pt d‐band vacancy and Pt electroactive surface area (Pt ECSA); this relationship was systematically evaluated by using X‐ray absorption (XAS), scanning electron microscopy (SEM) coupled with energy dispersive X‐ray spectroscopy (EDX), transmission electron microscopy (TEM), density functional theory (DFT) calculations, and electrochemical analyses. The MOR activity depends on two effects that act in cooperation, namely, the number of active Pt sites and their activity. Here the number of active Pt sites is associated with the Pt ECSA value, whereas the Pt‐site activity is associated with the alloying extent and Pt d‐band vacancy (electronic) effects. Among the Pt_xRu_100?x/C NPs with various Pt:Ru atomic ratios (x=25, 50, and 75), the Pt₇₅Ru₂₅/C NPs were shown to be superior in MOR activity on account of their favorable alloying extent, Pt d‐band vacancy, and Pt ECSA. This short study brings new insight into probing the synergistic effect on the surface reactivity of the Pt_xRu_100?x/C NPs, and possibly other bimetallic Pt‐based alloy NPs.     

微流控合成高活性甲醇氧化碳载铂钌电催化剂

报道了一种以微流控技术制备对甲醇具有高效电氧化催化活性的碳载PtRu催化剂(PtRu/C)的方法。 通过改变反应液在微流控反应器中的流速,得到了一系列纳米粒径分布在1.4~2.0 nm范围内的PtRu/C催化剂。 对这些催化剂进行电化学测试发现,当反应液以90 μL/min的流速流经微流控反应器时制得的催化剂具有最高催化活性。 进一步研究发现,这是由于在该流速制得的催化剂具有较大的电化学活性面积和较高含量的Pt(0)。 该种制备催化剂的方法在能源转化和环境领域有望被广泛使用。     

Heat-induced alterations in the surface population of metal sites in bimetallic nanoparticles

The ability to alter the surface population of metal sites in bimetallic nanoparticles (NPs) is of great interest in the context of heterogeneous catalysis. Here, we report findings of surface alterations of Pt and Ru metallic sites in bimetallic carbon-supported (PtRu/C) NPs that were induced by employing a controlled thermal-treatment strategy. The thermal-treatment procedure was designed in such a way that the particle size of the initial NPs was not altered and only the surface population of Pt and Ru was changed, thus allowing us to deduce structural information independent of particle-size effects. X-ray absorption spectroscopy (XAS) was utilized to deduce the structural parameters that can provide information on atomic distribution and/or extent of alloying as well as the surface population of Pt and Ru in PtRu/C NPs. The PtRu/C catalyst sample was obtained from Johnson Matthey, and first the as-received catalyst was reduced in 2 % H2 and 98 % Ar gas mixture at 300 degrees C for 4 h (PtRu/C as-reduced). Later this sample was subjected to thermal treatment in either oxygen (PtRu/C-O2-300) or hydrogen (PtRu/C-H2-350). The XAS results reveal that when the as-reduced PtRu/C catalyst was exposed to the O2 thermal-treatment strategy, a considerable amount of Ru was moved to the catalyst surface. In contrast, the H2 thermal-treatment strategy led to a higher population of Pt on the PtRu/C surface. Characterization of the heat-treated PtRu/C samples by X-ray diffraction and transmission electron microscopy reveals that there is no significant change in the particle size of thermally treated samples when compared to the as-received PtRu/C sample. The electrochemical properties of the as-reduced and heat-treated PtRu/C catalyst samples were confirmed by cyclic voltammetry, CO-adsorption stripping voltammetry, and linear sweep voltammetry. Both XAS and electrochemical investigations concluded that the PtRu/C-H2-350 sample exhibits significant enhancement in reactivity toward methanol oxidation as a result of the increased surface population of the Pt when compared to the PtRu/C-O2-300 and PtRu/C as-reduced samples.     

Preparation of polyaniline–tin dioxide composites and their application in methanol electro-oxidation

Polyaniline–tin dioxide (PANI-SnO₂) composites were prepared by chemical polymerization method, and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Due to the good stability in diluted acidic solution, PANI-SnO₂ composites were selected as the catalyst support and second catalyst for methanol electro-oxidation. The electrocatalytic properties of the PANI-SnO₂ supported Pt catalyst (Pt/PANI-SnO₂) for methanol oxidation have been investigated by cyclic voltammetry, chronoamperometry, and chronopotentiometry. Under the same loading mass of Pt, the Pt/PANI-SnO₂ catalyst shows higher electrocatalytic activity towards methanol electro-oxidation than Pt/SnO₂ catalyst.     

A Universal and Facile Way for the Development of Superior Bifunctional Electrocatalysts for Oxygen Reduction and Evolution Reactions Utilizing the Synergistic Effect

Increasing energy demands have stimulated intense research activities on reversible electrochemical conversion and storage systems with high efficiency, low cost, and environmental benignity. It is highly challenging but desirable to develop efficient bifunctional catalysts for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A universal and facile method for the development of bifunctional electrocatalysts with outstanding electrocatalytic activity for both the ORR and OER in alkaline medium is reported. A mixture of Pt/C catalyst with superior ORR activity and a perovskite oxide based catalyst with outstanding OER activity was employed in appropriate ratios, and prepared by simple ultrasonic mixing. Nanosized platinum particles with a wide range of platinum to oxide mass ratios was realized easily in this way. The as‐formed Pt/C–oxide composites showed better ORR activity than a single Pt/C catalyst and better OER activity than a single oxide to bring about much improved bifunctionality (ΔE is only ≈0.8 V for Pt/C–BSCF; BSCF=Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ), due to the synergistic effect. The electronic transfer mechanism and the rate‐determining step and spillover mechanism were two possible origins of such a synergistic effect. Additionally, the phenomenon was found to be universal, although the best performance could be reached at different platinum to oxide mass ratios for different oxide catalysts. This work thus provides an innovative strategy for the development of new bifunctional electrocatalysts with wide application potentials in high‐energy and efficient electrochemical energy storage and conversion.     

Nanoporous PtRu Alloys with Unique Catalytic Activity toward Hydrolytic Dehydrogenation of Ammonia Borane

Nanoporous (NP) PtRu alloys with three different bimetallic components were straightforwardly fabricated by dealloying PtRuAl ternary alloys in hydrochloric acid. Selective etching of aluminum from source alloys generates bicontinuous network nanostructures with uniform size and structure. The as‐made NP‐PtRu alloys exhibit superior catalytic activity toward the hydrolytic dehydrogenation of ammonia borane (AB) than pure NP‐Pt and NP‐Ru owing to alloying platinum with ruthenium. The NP‐Pt₇₀Ru₃₀ alloy exhibits much higher specific activity toward hydrolytic dehydrogenation of AB than NP‐Pt₃₀Ru₇₀ and NP‐Pt₅₀Ru₅₀. The hydrolysis activation energy of NP‐Pt₇₀Ru₃₀ was estimated to be about 38.9 kJ mol^?1, which was lower than most of the reported activation energy values in the literature. In addition, recycling tests show that the NP‐Pt₇₀Ru₃₀ is still highly active in the hydrolysis of AB even after five runs, which indicates that NP‐PtRu alloy accompanied by the network nanoarchitecture is beneficial to improve structural stability toward the dehydrogenation of AB.     

A simple one-step preparation of high utilization AuPt nanoparticles supported on MWCNTs for methanol oxidation in alkaline medium

A simple one-step preparation of gold–platinum electrocatalysts supported on multi-walled carbon nanotubes (MWCNTs) with high utilization is reported. A low Pt loading series of bimetallic AuPt/MWCNTs catalysts were prepared by the improved ethylene glycol reduction method, and then they were compared in terms of the electrocatalytic activity for methanol oxidation using cyclic voltammetry (CV) and chronoamperometry in alkaline solutions. The structure of AuPt/MWCNTs was characterized by the transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The results showed high Pt utilization, uniform AuPt nanoparticles size and good electrocatalytic activity for methanol electro-oxidation. The effect of Au/Pt mass ratio on electrocatalytic activity was also investigated by CV and chronoamperometry. The highest peak current density, lowest onset potential and best anti-poisoning effect for methanol electro-oxidation appeared at the Au/Pt/MWCNTs mass ratio of 2:4:32.     

Exploration of electrodeposited platinum alloy catalysts for methanol electro-oxidation in 0.5 M H<Subscript>2</Subscript>SO<Subscript>4</Subscript>: Pt-Ni system

In this work, we examine the electrocatalytic activity of electrodeposited Platinum (Pt)-Nickel (Ni) alloy layers on an inert substrate electrode for methanol oxidation reaction. Analyses using energy-dispersive fluorescent X-ray analysis and powder X-ray diffractometry confirm alloying of Pt with Ni in a range of compositions. Steady-state polarisation measurements in 0.5 M methanol+0.5 M H₂SO₄ solutions clearly show that the onset of electro-oxidation shifts to less anodic potential values (approximately 160 mV), while also exhibiting current enhancements up to ~15 times the currents obtained for the pure Pt electrodeposit. A linear relationship between the cyclic voltammetric peak (oxidation) current and [MeOH] is observed at a scan rate of 50 mVs^–1, thus indicating reduced influence of adsorbed CO (CO_ads) surface poison. A critical composition, Pt (92%)/Ni (8%) [denoted Pt-Ni(3) alloy] is found to exhibit maximum electrocatalytic activity, beyond which the activity drops, whereas pure Ni does not catalyse the reaction. While the promotion of electro-oxidation is understood to be largely due to the alloy catalyst, surface redox species of Ni oxide formed during the electro-oxidation process may also contribute to the oxygenation of CO_ads, thereby enhancing the oxidation current. Plausible mechanisms of methanol oxidation on Pt/ transition metal alloy electrocatalysts are discussed in terms of electron transfer (in the alloy) and the role of Ni oxide species.     

PtRu纳米线的合成及其在直接甲醇燃料电池阳极中的催化活性

 分别以SBA-15和MCM-41介孔分子筛作模板剂,采用浸渍还原法制备了纵横比及合金度不同的双组元PtRu纳米线和纳米棒电催化剂. 透射电镜、 X射线衍射表征和电化学测试结果表明, PtRu纳米线具有较高的合金度和较大的纵横比,在甲醇硫酸溶液中表现出更好的电催化活性. 初步探讨了PtRu纳米线催化剂的合金度和纵横比对其电催化活性和电极性能的影响.     

Pt/RuO2/CNTs纳米催化剂中RuO2含量对甲醇电催化氧化性能的影响

制备了一种新的甲醇直接燃料电池Pt/RuO2/CNTs阳极催化剂,在相同Pt负载量下,其甲醇电催化氧化活性是Pt/CNTs的3倍.采用循环伏安法研究发现Pt/RuO2/CNTs纳米催化剂中RuO2含量对甲醇电催化氧化活性有明显影响,当Pt和RuO2在碳纳米管上含量分别为15%和9.5%时,Pt/RuO2/CNTs催化剂具有最佳的甲醇电催化氧化活性.RuO2负载在碳纳米管上比电容的变化,反映了水合RuO2结构中质子与电子传输平衡的能力,分析表明,催化剂中RuO2含量不同导致电容的变化是影响甲醇电催化氧化活性的主要原因.当催化剂结构中质子与电子传输达到平衡时,催化剂比电容最大,电催化氧化活性最高.这种基于电容关联电催化剂的观点对甲醇直接燃料电池阳极催化剂的设计非常有意义.     

Catalytic activity and stability toward methanol oxidation of PtRu/CNTs prepared by adsorption in aqueous solution and reduction in ethylene glycol

In this paper, we reported an improved process for the preparation of PtRu/CNTs, which involves the adsorption of Pt and Ru ions on CNTs in aqueous solution and the reduction of the adsorbed Pt and Ru ions on CNTs in ethylene glycol. The surface morphology, structure, and compositions of the prepared catalyst were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy-dispersive spectrometer. TEM observation showed that the particles size of the prepared PtRu alloy was in the range of 2–5 nm, XRD patterns confirmed a face-centered cubic crystal structure. The activity and stability of the prepared catalyst toward methanol oxidation were studied in 0.5 M H₂SO₄ + 1 M CH₃OH solution by cyclic voltammetry, chronoamperometry, and chronopotentiometry. The electrochemical results showed that the prepared catalyst exhibited higher activity and stability toward methanol oxidation than commercial PtRu/C with the same loading amount of Pt and Ru.