Electroformation of Pd-modified Thin Film Electrocatalysts Using E-ALD Technique

Electrochemical atomic layer deposition was used to form bimetallic (BiPd, CuPd) and trimetallic (CuBiPd) thin films via surface-confined reactions. Pd thin films were characterized by cyclic voltammetry, scanning electron microscopy (SEM) and the alloy formation with preferred Au/Pd(111) orientation was confirmed by XRD. AFM revealed uniform grain distribution, with 3D islands growing on CuBiPd. EDX verified the presence of all deposited elements. Compared to other prepared catalysts, CuBiPd catalyst showed higher activity and stability towards the ethanol oxidation reaction (EOR), as confirmed by the peak current and onset potential trends, respectively: CuBiPd (1.35 mA, −0.450 V)>CuPd (0.6016 mA, −0.442 V)>BiPd (0.275 mA, −0.384 V)>Pd (0.186 mA, −0.350 V). The EOR current on CuBiPd improved by 2.5 folds relative to Pd. The results show that CuBiPd electrocatalyst is a promising material for EOR with enhanced catalytic properties for direct ethanol fuel cell     

Pd-Enriched-Core/Pt-Enriched-Shell High-Entropy Alloy with Face-Centred Cubic Structure for C1 and C2 Alcohol Oxidation

High-entropy alloy nanoparticles (HEA NPs) have aroused great interest globally with their unique electrochemical, catalytic, and mechanical properties, as well as diverse activity and multielement tunability for multi-step reactions. Herein, a facile low-temperature synthesis method at atmospheric pressure is employed to synthesize Pd-enriched-HEA-core and Pt-enriched-HEA-shell NPs with a single phase of face-centred cubic structure. Interestingly, the lattice of both Pd-enriched-HEA-core and Pt-enriched-HEA-shell enlarge during the formation process of HEA, with tensile strains included in the core and shell of HEA. The as-obtained PdAgSn/PtBi HEA NPs show excellent electrocatalytic activity and durability for methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). The specific (mass) activity of PdAgSn/PtBi HEA NPs for MOR is 4.7 mA cm⁻² (2874 mA mg_(Pd+Pt)⁻¹), about 1.7 (5.9) and 1.5 (4.8) times higher than that of commercial Pd/C and Pt/C catalysts, respectively. Additional to high-entropy effect, Pt sites and Pd sites on the interface of the HEA act synergistically to facilitate the multi-step process towards EOR. This study offers a promising way to find a feasible route for scalable HEA manufacturing with promising applications.     

钯原子修饰的金纳米颗粒乙醇氧化电催化剂

钯催化剂对碱性溶液的乙醇电催化氧化反应表现较好的催化活性. 本文通过简单的化学沉积法,将钯原子成功修饰到金纳米颗粒表面,制备的催化剂对乙醇电催化氧化反应表现出比钯更好的催化性能. 研究发现,钯原子不均匀地覆盖在金核表面,部分金原子暴露在外层. 制备的催化剂的峰电流密度是钯催化剂的4.6 倍,起始电势低100 mV. 该催化剂较好的催化性能可能归因于金核的电子效应和表面双功能电催化反应机制.     

Palladium Adatoms on Gold Nanoparticles as Electrocatalysts for Ethanol Electro-Oxidation in Alkaline Solutions; [钯原子修饰的金纳米颗粒乙醇氧化电催化剂]北大核心CSCD

Palladium (Pd) is a good catalyst for ethanol electro-oxidation in alkaline solutions.The activity of Pd is further improved in this study by modifying the gold (Au) nanoparticles with Pd adatoms using a simple spontaneous deposition process.The Pd overlayer on the Au core (Au@Pd) is un-uniform with some Au atoms exposed to the electrolyte.The activity of Au@Pd/C toward ethanol oxidation reaction (EOR) is much higher than that of Pd/C in an alkaline solution.The peak current density of Au@Pd/C is 4.6 times higher than that of Pd/C with a 100 mV lower onset potential.The enhanced activity may be due to the electronic effect from the Au core, and the bifunctional reaction mechanism. © 2018 Journal of Electrochemistry. All rights reserved.     

A high dispersed Pt0.35Pd0.35Co0.30/C as superior catalyst for methanol and formic acid electro-oxidation

Pt：Pd：Co ternary alloy nanoparticles were synthesized by sodium borohydride reduction under nitrogen, and were supported on carbon black as catalysts for methanol and formic acid electro-oxidation. Compared with Pt0.65C00.35/C, Pt/C, Pd0.65C00.35/C, and Pd/C catalyst, Pt0.35Pd0.35Co0.30/C exhibited relatively high durability and strong poisoning resistance, and the Pt-mass activity was 3.6 times higher than that of Pt/C in methanol oxidation reaction. Meanwhile, the Pt0.35Pd0.35Co0.30/C exhibited excellent activity with higher current density and higher CO tolerance than that of Pt0.6sCo0.35/C, Pt/C, Pd0.65C00.35/ C, and Pd/C in formic acid electro-oxidation.     

PdCoIr四面体合金纳米催化剂的制备及其对乙醇氧化的电催化性能

钯(Pd)基催化剂是直接乙醇燃料电池研究中广泛使用的催化剂,进一步提升其性能是推动燃料电池发展的重要方向.本文用一步水热法制备出四面体结构PdCo(PdCo tetrahedron,记为PdCo-TH)和少量铱(Ir)掺杂的PdCo四面体合金纳米粒子(记为PdCoIr-TH).经TEM、ICP、XPS 及CV 等表征证...     

浸渍顺序对Ag-Pd/Ce0.8Zr0.2O2催化剂活性及脱附性能的影响

 采用不同的浸渍顺序制备了Ag-Pd/Ce0.8Zr0.2O2双组分催化剂,考察了催化剂对乙醇和CO氧化反应的催化活性,并对催化剂进行了TPD表征. 结果表明,浸渍顺序对催化剂的活性有很大的影响. 共浸渍催化剂的活性最高,其次为先浸渍钯后浸渍银的催化剂,先浸渍银后浸渍钯催化剂的活性最低. 催化剂上CO氧化活性与CO-TPD过程中CO2脱附峰的温度及强度有对应关系. 同时,乙醇氧化活性与C2H5OH-TPD过程中CO2脱附峰的温度有一定的对应关系. 这表明共浸渍催化剂的表面氧物种最活泼,最容易与吸附在催化剂表面的乙醇或CO发生氧化反应. 不同的浸渍顺序影响Ag或Pd的存在状态,共浸渍时有利于氧化态的形成; 但Ag状态的变化与催化剂上乙醇或CO氧化反应的活性没有对应关系.     

低结晶度AuPt-Ru/CNTs合金异质结作为高效多功能电催化剂

催化剂的活性与其结构紧密相关,研究催化剂的构效关系以及可控合成高效电催化剂, 并探究其催化机制, 一直是科学研究的核心。贵金属铂是优异的电解水析氢的催化剂, 同时也是直接醇燃料电池阳极氧化的良好催化剂,而贵金属钌是优异的电解水析氧催化剂。这些与燃料电池及氢能相关的重要反应催化剂,可通过合成Pt、Au及Ru的合金催化剂, 通过应力效应、电子效应及团簇效应, 可有效提高金属催化剂的活性, 并实现多功能电催化性能。本文报道了可控合成低结晶度的AuPt-Ru合金异质结,并通过元素扫描分析及X射线衍射分析确认其结构。该催化剂表现出了非常优异的电催化氧化乙醇活性, 其归一化到Pt的质量活性达到了为21.4 A·mg^-1_Pt, 远远高于对照组样品AuPt及RuAuPt混合相催化剂及文献报道样品。催化剂同样表现出了非常好的乙醇氧化稳定性, 但是其活性的衰减与其Ru组分的流失紧密相关。我们同时通过电化学原位红外光谱,研究了该催化剂乙醇氧化中间产物, 分析了其反应机理。该催化剂同样表现出了优异的碱性电解水析氢及析氧催化活性,其析氢电流10 mA·cm^-2对应的过电位为30 mV, Tafel斜率为45 mV·dec^-1, 优于AuPt及RuPtAu对照组样品。该催化剂优异的电化学性能主要归结于其低结晶度和异质结及其伴随的应力效应及团簇效应。本报道提供了一种可控合成具有异质结结构的金属合金催化剂, 突出了其对实现多功能、 高性能合金电催化剂的重要性。     

Palladium Encapsulated by an Oxygen-Saturated TiO2 Overlayer for Low-Temperature SO2-Tolerant Catalysis during CO Oxidation

The development of oxidation catalysts that are resistant to sulfur poisoning is crucial for extending the lifespan of catalysts in real-working conditions. Herein, we describe the design and synthesis of oxide-metal interaction (OMI) catalyst under oxidative atmospheres. By using organic coated TiO₂, an oxide/metal inverse catalyst with non-classical oxygen-saturated TiO₂ overlayers were obtained at relatively low temperature. These catalysts were found to incorporate ultra-small Pd metal and support particles with exceptional reactivity and stability for CO oxidation (under 21 vol % O₂ and 10 vol % H₂O). In particular, the core (Pd)-shell (TiO₂) structured OMI catalyst exhibited excellent resistance to SO₂ poisoning, yielding robust CO oxidation performance at 120 °C for 240 h (at 100 ppm SO₂ and 10 vol % H₂O). The stability of this new OMI catalyst was explained through density functional theory (DFT) calculations that interfacial oxygen atoms at Pd−O−Ti sites (of oxygen-saturated overlayers) serve as non-metal active sites for low-temperature CO oxidation, and change the SO₂ adsorption from metal(d)-to-SO₂(π*) back-bonding to much weaker σ(Ti−S) bonding.     

Synthesis of gold and palladium nanoparticles supported on CuO/rGO using imidazolium ionic liquid for CO oxidation

A simple ionic liquid-assisted approach for the fabrication of graphene-based nanocomposite is reported. Pd–CuO/rGO and Au–CuO/rGO nanocomposites are successfully fabricated with the assistance of the ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate. The physicochemical features of nanocomposite are systematically characterized by XRD, FT-IR, Raman spectroscopy, XPS, TGA, FESEM, AFM, and HRTEM. Carbon monoxide has been used as a probe molecule to emphasize the performance of the fabricated materials. The results indicate that the incorporation of a little quantity of ionic liquid results in the creation of uniformly dispersed NPs simultaneously with the reduction of graphene oxide (GO) into rGO, which leads to a low-temperature CO oxidation process. Besides, the Au–CuO/rGO catalyst achieved excellent durability in CO oxidation for 14 h, without detectable deactivation. The low-temperature CO oxidation was mainly induced by the synergistic effects between the components of catalysts. The Au or Pd and CuO combination not only generates more interfaces, which is more favorable for the activation of oxygen but also enhances the catalyst reduction behavior. Consequently, a graphene composite catalyst can be considered a potential CO oxidation candidate.

     

电解液中的乙二胺四甲叉膦酸对甲酸在炭载Pd催化剂上电氧化性能的影响

利用X射线能量色散(EDS)谱、X射线衍射(XRD)谱、透射电子显微镜(TEM)和电化学等技术研究了在电解液中添加乙二胺四甲叉膦酸(EDTMP)对甲酸在Pd/C催化剂上电氧化性能的影响. 结果表明, 当EDTMP添加的浓度为0.5 mmol/L时, Pd/C催化剂对甲酸氧化的电催化活性和稳定性最好. 这主要归结于吸附在Pd/C催化剂表面的EDTMP不但能通过基团效应降低CO的吸附量, 还能抑制Pd/C催化剂催化甲酸分解的速率, 从而减少了CO的毒化作用. 但当EDTMP的浓度大于0.5 mmol/L时, 吸附过多的EDTMP反而会占据Pd的活性位点, 降低催化作用.     

Interfacial Engineering in PtNiCo/NiCoS Nanowires for Enhanced Electrocatalysis and Electroanalysis

Searching for new anti-poisoning Pt-based catalysts with enhanced activity for alcohol oxidation is the key in direct alcohol fuel cells (DAFCs). However, in the traditional strategy for designing bimetallic or multimetallic alloy is still difficult to achieve a satisfactory heterogeneous electrocatalyst because the activity often depends on only the surface atoms. Herein, we fabricate the multicomponent active sites by creating a sulfide structure on 1D PtNiCo trimetallic nanowires (NWs), to give a PtNiCo/NiCoS interface NWs (IFNWs). Owing to the presence of sulfide interfaces, the PtNiCo/NiCoS IFNWs enable an impressive methanol/ethanol oxidation reaction (MOR/EOR) performance and excellent anti-CO poisoning tolerance. They have the MOR and EOR mass activities of 2.25 Amg^-1_Pt and 1.62 Amg^-1_Pt, around 1.26, 3.21 and 1.46, 2.96 times higher than those of PtNiCo NWs and commercial Pt/C, respectively. CO-stripping and XPS measurements further demonstrate that the new interfacial structure and optimal bonding of Pt−CO can result in accelerating the removal of surface adsorbed carbonaceous intermediates. Moreover, such a unique structure has also demonstrated a much-improved ability for the electrochemical detection of some important molecules (H₂O₂ and NH₂NH₂).     

还原剂对Au-Pd/CeO2催化剂甲醇部分氧化性能的影响

以PVP为保护剂,乙醇(ER)、乙二醇(GR)和水合肼(HR)为还原剂制备了一系列Au-Pd/CeO2催化剂,考察了还原剂对甲醇部分氧化性能的影响,并运用XRD、TPD和TPR等手段对催化剂进行了表征。结果表明,Au-Pd/CeO2(ER)催化剂具有较大的比表面积,形成的AuxPdy量较多、粒径较小、分散度较高、活性组分与载体的相互作用较强,同时对甲醇的吸附量较大和吸附温度较低。因此,该催化剂具有较高的催化活性和氢气选择性以及较低的CO质量分数。     

Pd/WO_3-RGO纳米催化剂对甲酸氧化的电催化性能

采用表面修饰技术将WO_3晶粒引入到氧化石墨烯(GO)表面,通过硼氢化钾还原法制备了载钯催化剂Pd/WO_3-RGO.对催化剂进行了结构和形貌表征,并考察了该催化剂对甲酸氧化的电催化性能.结果表明,Pd/WO_3-RGO催化剂由石墨烯、单斜态WO_3和立方面心Pd晶粒组成,Pd颗粒均匀分散在载体上;使用Pd/20%WO_3-RGO催化剂电极时的甲酸氧化最大峰电流密度大幅增加,是Pd/RGO催化剂电极甲酸氧化峰电流密度的2.5倍;Pd/WO_3-RGO催化剂稳定性大大增强,且具有更加优异的抗CO中毒能力;Pd晶粒与WO_3晶粒的相互交叠有利于它们之间的催化协同效应,增强催化剂的催化性能.     

离子液体中水热合成Pt-Pd/MWCNTs和Pd/MWCNTs催化剂

采用水热合成法, 以离子液体1-乙基-3-甲基咪唑四氟硼酸盐(C₆H₁₁BF₄N₂, EMIBF₄)为溶剂制备了Pt-Pd/MWCNTs(Multi-walled carbon nanotubes)和Pd/MWCNTs催化剂. X射线衍射(XRD)和X射线能量散射谱(EDS)测试证明了Pt-Pd合金和Pd纳米颗粒在MWCNTs的表面生成. 透射电子显微镜(TEM)照片不仅证明了在MWCNTs表面Pt-Pd, Pd纳米颗粒的生成, 而且还表明样品颗粒的平均粒径约为4 nm. 循环伏安(CV)和交流阻抗(EIS)测试表明, 在碱性环境下, 乙醇在Pt-Pd/MWCNTs和Pd/MWCNTs修饰的玻碳(GC)电极上均能发生氧化反应, 与Pd/MWCNTs修饰的电极相比, 在Pt-Pd/MWCNTs上乙醇的起峰电位负移了大约200 mV, 且具有更高的氧化峰电流值.     

浸渍法制备硅钨酸修饰的炭载钯催化剂电催化甲酸氧化

用浸渍的方法制备了硅钨酸（SiWA）修饰的炭载Pd(Pd/C-SiWA)催化剂。 计时电流曲线研究表明,在Pd/C和Pd/C-SiWA催化剂电极上,3000 s时的电流密度分别为0.013和0.082 A/mg,分别为10 s时电流密度的2.5%和14.1%。 结果表明,Pd/C-SiWA催化剂对甲酸氧化的电催化稳定性要远远优于Pd/C催化剂。 这是因为Pd/C催化剂上SiWA的修饰抑制了甲酸的自分解, 从而减小了CO的毒化作用,改进了Pd/C催化剂对甲酸氧化的电催化和稳定性。     

Accelerating Ethanol Complete Electrooxidation via Introducing Ethylene as the Precursor for the C−C Bond Splitting

The crucial issue restricting the application of direct ethanol fuel cells (DEFCs) is the incomplete and sluggish electrooxidation of ethanol due to the chemically stable C−C bond thereof. Herein, a unique ethylene-mediated pathway with a 100 % C1-selectivity for ethanol oxidation reaction (EOR) is proposed for the first time based on a well-structured Pt/Al₂O₃@TiAl catalyst with cascade active sites. The electrochemical in situ Fourier transform infrared spectroscopy (FTIR) and differential electrochemical mass spectrometry (DEMS) analysis disclose that ethanol is primarily dehydrated on the surface of Al₂O₃@TiAl and the derived ethylene is further oxidized completely on nanostructured Pt. X-ray absorption and density functional theory (DFT) studies disclose the Al component doped in Pt nanocrystals can promote the EOR kinetics by lowering the reaction energy barriers and eliminating the poisonous species. Strikingly, Pt/Al₂O₃@TiAl exhibits a specific activity of 3.83 mA cm⁻²_Pt, 7.4 times higher than that of commercial Pt/C and superior long-term durability.     

Unraveling the surface reactions during liquid-phase oxidation of benzyl alcohol on Pd/Al2O3: an in situ ATR-IR study

The palladium-catalyzed liquid-phase reaction of benzyl alcohol to benzaldehyde was investigated in the presence and absence of oxygen by attenuated total reflection infrared (ATR-IR) spectroscopy. The 5 wt % Pd/Al2O3 catalyst was fixed in a flow-through ATR-IR cell serving as a continuous-flow reactor. The reaction conditions (cyclohexane solvent, 323 K, 1 bar) were set in the range commonly applied in the heterogeneous catalytic aerobic oxidation of alcohols. The in situ ATR-IR study of the solid-liquid interface revealed a complex reaction network, including dehydrogenation of benzyl alcohol to benzaldehyde, decarbonylation of benzaldehyde, oxidation of hydrogen and CO on Pd, and formation of benzoic acid catalyzed by both Pd and Al2O3. Continuous formation of CO and its oxidative removal by air resulted in significant steady-state CO coverage of Pd during oxidation of benzyl alcohol. Unexpectedly, benzoic acid formed already in the early stage of the reaction and adsorbed strongly (irreversibly) on the basic sites of Al2O3 and thus remained undetectable in the effluent. This observation questions the reliability of product distributions conventionally determined from the liquid phase. The occurrence of the hydrogenolysis of the C-O bond of benzyl alcohol and formation of toluene indicates that Pd was present in a reduced state (Pd0) even in the presence of oxygen, in agreement with the dehydrogenation mechanism of alcohol oxidation.     

One‐Pot Synthesis of Carbon‐Supported Dendritic Pd‐Au Nanoalloys for Electrocatalytic Ethanol Oxidation

One‐pot synthesis of carbon‐supported Pd‐Au alloy nanoparticles with well‐defined dendritic shape (Pd‐Au_den/C) was achieved by co‐reduction of K₂PdCl₄/HAuCl₄ mixtures in a molar ratio of 1:1 with hydrazine in the presence of Vulcan XC‐72R. The prepared Pd‐Au_den/C exhibited significantly enhanced performance in the electrocatalytic oxidation of ethanol compared with dendritic Pd nanoparticles and a commercial Pd/C catalyst. Pd‐Au_den/C even showed higher durability in electro‐oxidation of ethanol than the supported catalyst prepared by the deposition of presynthesized dendritic Pd‐Au nanoparticles on the carbon support. The experimental results clearly indicate that enhanced interaction between nanoparticle catalysts and carbon support through the one‐pot synthesis protocol can improve the durability of the electrocatalysts.     

CO and C3H8 Total Oxidation over Pd Catalysts Supported on Commercial Ce-Zr Solid Solution: Effects of the Calcination Temperature and Hydrothermal Treatment

A series of Pd catalysts supported on commercial Ce-Zr solid solution(Pd/CZ) calcined at different temperatures(750, 900 and 1050 ℃) was prepared via an incipient wetness impregnation method. The activities of the fresh and hydrothermally aged Pd/CZ catalysts were tested for total oxidation of CO and C₃H₈. For CO oxidation, the activity of either fresh or aged Pd/CZ catalysts decreased with the elevating of calcination temperature of CZ support, with a fresh catalyst calcined at 750 ℃ possessing the highest activity and hydrothermal stability. For C₃H₈ total oxidation, the activity of Pd/CZ catalysts could be improved by increasing the calcination temperature of support. However, the aged Pd/CZ catalysts showed higher activity than corresponding fresh Pd/CZ catalysts. The turnover frequency(TOF) over Pd/CZ catalyst for CO oxidation increased with increasing reduction ability of the catalysts, with a fresh catalyst calcined at 750 ℃ having the highest value(0.27 s^-1). However, the TOF of Pd/CZ catalyst for C₃H₈ total oxidation was mainly affected by the size of Pd particles, and large Pd particles possessed a higher activity, with the highest TOF value(0.96 s^-1) obtained over an aged catalyst calcined at 1050 ℃.