Nanosized palladium on holey graphene sheets incorporating PxOy for effective formic acid oxidation

A stack of basic structural carbon units incorporating phosphorus oxides (P_xO_y) at edges and internal defects is obtained and used as a support material for Pd nanoparticles, with the aim of creating an efficient electrocatalyst for HCOOH oxidation. In contrast to the lack of activity displayed by Pd supported on lyophilized and vacuum-annealed graphene oxides, Pd on holey graphene sheets incorporating P_xO_y (Pd/HGP_xO_y) shows efficient activity and stability in HCOOH oxidation. Surface analysis of fresh and reacted catalysts reveals that HCOOH oxidation is favored by Pd/HGP_xO_y due to the decreased Pd electron density caused by electron transfer from Pd to HGP_xO_y.     

Pd black decorated by Pt sub-monolayers as an electrocatalyst for the HCOOH oxidation

Pd black was modified by a very low amount of Pt corresponding to a sub-monolayer (ML). Spontaneous displacement method was employed. The catalysts with 0.02–0.12 ML were characterized by cyclic voltammetry and CO_ads stripping and were tested for HCOOH oxidation under the potentiodynamic and potentiostatic conditions. All the Pt@Pd catalysts were more active for HCOOH oxidation than Pd black. The Pt@Pd with 0.08 ML of Pt exhibited the highest activity with the maximum current density under the potentiodynamic conditions of 8 mA cm^?2 (vs. 2.7 mA cm^?2 on Pd black). Contrasting HCOOH oxidation kinetics on Pt@Pd and Pt@Au catalysts revealed that the current densities are higher, and the poisoning rate is lower on Pt@Pd catalyst. This was ascribed to an optimal strength of the Pt–adsorbate bond when Pt is supported on Pd and to a possible influence of the Pt atoms on the Pd substrate.     

镀Pd的GC电极上HCOOH的电催化氧化

在玻璃碳 (GC)基底上电沉积Pd ,应用SEM观测Pd沉积层的表面形貌 ,用循环伏安法研究了Pd/GC电极上HCOOH在HClO4溶液中的电氧化行为 .结果表明 ,Pd的电沉积条件影响电极的催化性能 .在高电流密度下制得的Pd/GC电极对HCOOH的电氧化具有比纯Pd电极更高的催化活性 .当电极表面生成PdO时 ,HCOOH被电氧化的活性很低 ,而在PdO还原后生成的Pd表面 ,HCOOH的电氧化显示极高的活性 .本文还讨论了Pd(Ⅱ )离子对HCOOH电氧化过程的影响 .     

负载于刻蚀镍泡沫上钯纳米粒子作为乙醇氧化高性能电催化剂

发展具有高催化活性和高稳定性的非Pt阳极催化剂目前仍面临着巨大的挑战. 除了设计催化剂以外,设计合适的载体对提高电催化剂性能也具有重要意义. 在这篇论文中,作者报导了一种以混合酸(HNO₃+H₂SO₄+H₃PO₄+CH₃COOH) 腐蚀的镍泡沫负载Pd纳米粒子作为高性能电催化剂用于碱性条件下乙醇氧化. 因具有开放孔结构、快速电解质渗透能力及快速的电荷传输性能,这些镍泡沫负载的Pd纳米粒子显示了很好的电催化活性和循环稳定性,显示了该材料在乙醇阳极氧化具有较好的应用前景.     

The formation of palladium nanocomposite catalysts on the porous silicon used as anodes of fuel cells

Palladium nanoparticles on the porous silicon were synthesized by radiation-chemical reduction in the solution of reversed micelles. The Pd nanoparticles obtained are electron deficient. The porosity, the type of conductivity, the silicon matrix pore geometry, and precursor parameters influence the size, the shape and the charge state of palladium catalysts. The mechanism of H₂ and HCOOH electrooxidation on porous silica in the presence of Pd+/Pd redox pair is proposed.     

Formation and electrocatalytic properties of Pd deposits on Mo obtained by galvanic displacement

A Pd-Mo electrocatalytic system was obtained by forming palladium particles on the Mo surface that contacted a PdCl₂ solution under open-circuit conditions. The state of palladium on the electrode surface depended on the contact displacement time. Palladium particles 5–10 nm in size formed on the surface of the Pd(Mo) electrode after palladium deposition for 1 min. The specific rates of formic acid oxidation on the Pd(Mo) electrode were smaller than those on the Pd/Pt electrode. On the Pd(Mo) electrode, anode currents of methanol oxidation were recorded at a potential of 0.4 V. The difference in the effects of the Mo substrate on the activity of Pd particles in the electrooxidations of HCOOH and CH₃OH was explained by the difference in the mechanisms of these reactions.     

一种新型的甲酸/铁离子燃料电池

以甲酸为燃料、 Fe³⁺为氧化剂组成了一种新型的甲酸/铁离子燃料电池, 阳极催化剂为多壁碳纳米管(MWCNT)或β-环糊精修饰的MWCNT(β-CD-MWCNT)负载的金属钯或钯锡纳米颗粒: PdSn/MWCNT, Pd/β-CD-MWCNT和PdSn/β-CD-MWCNT. 运用循环伏安(CV)和计时电流(CA)等技术研究了各催化剂在碱性条件下对甲酸氧化反应的电催化活性. 结果表明, 加入适量的金属锡能促进钯对甲酸的电催化氧化, 甲酸氧化电位提前, 电流密度增加; 环糊精的改性对催化剂电催化活性有一定提升. 将上述催化剂制成电池阳极片, 碳粉制成电极阴极片, 组成甲酸/铁离子燃料电池并测试其放电性能. 结果表明, 电池的开路电压在0.981.20 V之间; 以PdSn/β-CD-MWCNT为阳极时, 其最大放电电流密度达50 mA/cm², 最大功率密度达12.6 mW/cm², 远优于以Pd/C为阳极的电池性能.     

钯催化甲酸为氢源的芳硝基化合物直接加氢和一锅法酰胺化

Pd/C催化剂实现了甲酸为氢源的芳硝基化合物的直接加氢及甲酸为氢源和羰基源的一锅法芳硝基化合物的酰胺化.在芳硝基化合物的直接加氢过程中,该体系体现了很好的催化活性,实现了对同时带有其它可还原官能团的芳硝基化合物的选择性加氢,得到较高收率的胺类化合物.同时,通过提高反应温度和增加甲酸的量,实现了芳硝基化合物的加氢和甲酰化的串联反应,该体系体现了较高的催化活性.     

Self-assembly of mixed Pt and Au nanoparticles on PDDA-functionalized graphene as effective electrocatalysts for formic acid oxidation of fuel cells

Pt and Au nanoparticles with controlled Pt?:?Au molar ratios and PtAu nanoparticle loadings were successfully self-assembled onto poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene (PDDA-G) as highly effective electrocatalysts for formic acid oxidation in direct formic acid fuel cells (DFAFCs). The simultaneously assembled Pt and Au nanoparticles on PDDA-G showed superb electrocatalytic activity for HCOOH oxidation, and the current density associated with the preferred dehydrogenation pathway for the direct formation of CO(2) through HCOOH oxidation on a Pt(1)Au(8)/PDDA-G (i.e., a Pt?:?Au ratio of 1?:?8) is 32 times higher than on monometallic Pt/PDDA-G. The main function of the Au in the mixed Pt and Au nanoparticles on PDDA-G is to facilitate the first electron transfer from HCOOH to HCOO(ads) and the effective spillover of HCOO(ads) from Au to Pt nanoparticles, where HCOO(ads) is further oxidized to CO(2). The Pt?:?Au molar ratio and PtAu nanoparticle loading on PDDA-G supports are the two critical factors to achieve excellent electrocatalytic activity of PtAu/PDDA-G catalysts for the HCOOH oxidation reactions.     

From HCOOH to CO at Pd electrodes: a surface-enhanced infrared spectroscopy study

The decomposition of HCOOH on Pd surfaces over a potential range of practical relevance to hydrogen production and fuel cell anode operation was probed by combining high-sensitivity in situ surface-enhanced IR spectroscopy with attenuated total reflection and thin-layer flow cell configurations. For the first time, concrete spectral evidence of CO(ad) formation has been obtained, and a new main pathway from HCOOH to CO(ad) involving the reduction of the dehydrogenation product of HCOOH (i.e., CO(2)) is proposed.     

Graphene nanoplatelets supported metal nanoparticles for electrochemical oxidation of hydrazine

Graphene nanoplatelets have been applied as the support to electrodeposit monometallic Au and Pd nanoparticles as well as bimetallic Au–Pd nanoparticles. These nanoparticles have been characterized with scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and electrochemical techniques. They are further utilized as the catalysts for electrochemical oxidation of hydrazine. The oxidation peak potential is − 0.35 and 0.53 V (vs. SCE) when monometallic Pd and Au nanoparticle are used as the catalysts. When bimetallic nanoparticles are applied as the catalyst, their composition affects the peak potential and peak current for the oxidation of hydrazine. Higher oxidation current is achieved when bimetallic Au–Pd nanoparticles with an atomic ratio of 3:1 are deposited on graphene nanoplatelets. Metal nanoparticle-loaded graphene nanoplatelets are thus novel platforms for electrocatalytic, electroanalytical, environmental, and related applications.     

The study of the active surface for CO oxidation over supported Pd catalysts

CO oxidation was investigated on various powder oxide supported Pd catalysts by temperature-programmed reaction.The pre-reduced catalysts show significantly higher activities than the pre-oxidized ones.Model studies were performed to better understand the oxidation state,reactivities and stabilities of partially oxidized Pd surfaces under CO oxidation reaction conditions using an in situ infrared reflection absorption spectrometer(IRAS).Three O/Pd(100)model surfaces,chemisorbed oxygen covered surface,surface oxide and bulk-like surface oxide,were prepared and characterized by low-energy electron diffraction(LEED)and Auger electron spectroscopy(AES).The present work demonstrates that the oxidized palladium surface is less active for CO oxidation than the metallic surface,and is unstable under the reaction conditions with sufficient CO.     

Polyvinyl alcohol-modified graphene oxide as a support for bimetallic Pt–Pd electrocatalysts to enhance the efficiency of formic acid oxidation

The aim of this research was to study the efficiency of polyvinyl alcohol (PVA)-modified graphene oxide (GO) as a supporting material for catalysts that oxidize formic acid. The active metal catalysts (e.g., Pt and Pd) were electrodeposited on PVA/GO surfaces. The morphologies of the prepared catalysts were characterized by scanning electron microscopy and transmission electron microscopy, while their chemical compositions were identified by X-ray diffraction and X-ray photoelectron spectroscopy. The results show that compared with the other catalysts on GO, the prepared active PtPd alloy catalyst nanoparticles with 11.49–20.73 nm sizes were well dispersed on the PVA/GO surfaces. Electrochemical results indicate that the activities of the catalysts with PVA provided a higher current density than that of the catalysts without PVA. The bimetallic 3Pt3Pd/PVA/GO catalyst showed the greatest catalytic activity, stability, and CO oxidation when compared to those of other catalysts. The electronic, morphological, and structural properties promote the mass-charge transfer through the interaction. These results indicate that the PVA-modified GO provides a suitable site for active bimetallic catalyst surfaces, resulting in excellent formic acid oxidation and high CO elimination. The 3Pt3Pd/PVA/GO electrocatalyst is promising for enhancing formic acid oxidation.     

炭载Pd-Pb合金纳米粒子对甲酸电催化氧化的影响

通过浸渍还原方法制备了具有不同化学计量比的炭载Pd-Pb合金纳米粒子催化剂. XRD和TEM测试结果表明, Pd-Pb合金纳米粒子的晶格常数随Pb元素含量的增加而增加, 相应的粒子尺寸随Pb元素含量的增加而减小. 循环伏安、CO溶出和计时电流等电化学测试结果表明, 炭载Pd-Pb合金纳米粒子催化剂对甲酸氧化的电催化活性随Pb含量的增加而降低.     

单原子分散的Ir-N-C燃料电池阳极抗中毒催化剂

燃料电池的阳极抗中毒研究是重要课题,探索具有超高质量活性和抗CO毒化的阳极催化剂具有显著的科学意义和应用价值。本文成功制备了Ir原子级别分散在N掺杂碳的载体上的新催化剂,并且发现该Ir-N-C对甲酸具有良好的电催化氧化性能,其质量比活性为商业Pd/C的48倍。组装了燃料电池单电池进行测试,结果显示,Ir-N-C催化剂在单电池中的质量比功率密度高达281 mW/mg,较商业Pd/C催化剂提升了3倍。同时,Ir-N-C对CO毒化的耐受性大大增强,经过14000 s的长期测试后,其活性仅衰减68%,优于商业Pd/C催化剂（衰减85%）。并且,该催化剂能够简单有效的大批量制备,为单原子催化剂的大批量制备提供了新思路。     

Efficient Catalytic Production of Hydrogen Peroxide Using Tin-containing Zeolite Fixed Palladium Nanoparticles with Oxidation Resistance

The metal surfaces tend to be oxidized in air through dissociation of the O−O bond of oxygen to reduce the performances in various fields. Although several ligand modification routes have alleviated the oxidation of bulky metal surfaces, it is still a challenge for the oxidation resistance of small-size metal nanoparticles. Herein, we fixed the small-size Pd nanoparticles in tin-contained MFI zeolite crystals, where the tin acts as an electron donor to efficiently hinder the oxidation of Pd by weakening the adsorption of molecular oxygen and suppressing the O−O cleavage. This oxidation-resistant Pd catalyst exhibited superior performance in directly synthesizing hydrogen peroxide from hydrogen and oxygen, with the productivity of hydrogen peroxide at ≈10,170 mmol g_Pd⁻¹ h⁻¹, steadily outperforming the catalysts tested previously. This work leads to the hypothesis that tin is an electron donor to realize oxidation-resistant Pd within zeolite crystals for efficient catalysis to overcome the limitation of generally supported Pd catalysts and further motivates the use of oxidation-resistant metal nanoparticles in various fields.     

Performance study of palladium modified platinum anode in direct ethanol fuel cells: A green power source

The direct ethanol fuel cell is a green and renewable power source alternative to fossil fuels and produces less emissions compared to a combustion engine. Ethanol can be generated in great quantity from renewable resources like biomass through a fermentation process. Bio-generated ethanol is thus attractive fuel since growing crops for biofuels absorbs much of the carbon dioxide emitted into the atmosphere from the oxidation of ethanol. The platinum and palladium were co-deposited on graphite substrate by the galvanostatic technique and employed as anode catalyst for ethanol electrooxidation. The information on surface morphology, structural characteristics and bulk composition of the catalyst was obtained using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy. The cyclic voltammetry (CV) were used for the estimation of the electrochemically active surface area (ECSA) of the synthesized catalysts in alkaline medium. The CVs for ethanol oxidation revealed superior catalytic activity of Pt–Pd/C compared to Pd/C and Pt/C. The effect of OH^? on ethanol oxidation at Pt–Pd/C catalyst was studied using cyclic voltammetry, quasisteady-state polarization, chronoamperometry, and electrochemical impedance spectroscopy (EIS). The Pt–Pd/C catalyst shows good stability and enhanced electrocatalytic activity is ascribed to the synergistic effect of higher electrochemical surface area, preferred OH^? adsorption on the surface and palladium ad-atom contribution on the alloyed surface.     

Pd-Sb/C复合纳米催化剂对甲酸电催化氧化的性能研究

以柠檬酸三钠为稳定剂,硼氢化钠为还原剂,制备了碳载型的Pd-Sb复合纳米催化剂（Pd-Sb/C）,通过调制不同Pd:Sb摩尔比研究了其对甲酸电催化性能的影响. TEM结果表明,合成的纳米颗粒粒径较小且均匀分散在碳载体表面. XRD和XPS测试表明,Pd-Sb/C中少量的单质态Sb(0)高度分散在Pd颗粒中或表面,形成合金化程度较低的PdSb合金. 电化学测试表明,当Pd:Sb = 20:1时,合成的催化剂对甲酸的催化效能最佳. 与合成的Pd/C和商业Pd/C相比,Pd-Sb/C(20:1)的电流密度分别是Pd/C的2.6倍、商业Pd/C的4.2倍. Pd-Sb/C的整体催化性能得到改善主要归因于适量的单质态Sb(0)引入到Pd中,诱导产生电子效应和“双功能”效应,一方面减小Pd与CO毒性物种之间的吸附作用,另一方面促使Pd表面吸附的CO快速氧化,提高了Pd-Sb/C催化剂的抗CO中毒能力,使得Pd-Sb/C催化剂的整体催化性能得到改善.     

不同载体负载Pd催化剂对甲酸的电催化氧化活性比较

应用Hummers法氧化合成氧化石墨(GO), 然后用化学一步还原法制得石墨烯（graphene）负载Pd催化剂. 用同样方法以多壁碳纳米管（MWCNTs）、单壁碳纳米管（SWCNTs）和Vulcan XC-72为载体制备了不同负载型的Pd催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明,在石墨烯载体上Pd纳米粒子粒径较小,且分布均匀. 电化学活性面积(ECSA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)电化学测试显示, 与其它3种碳载体的Pd催化剂相比, 石墨烯负载Pd催化剂对甲酸电催化氧化的催化活性和稳定性最好.     

Carbon-supported PdSn nanoparticles as catalysts for formic acid oxidation

Pd and PdSn nanoparticles supported on Vulcan XC-72 carbon are prepared by a microwave-assisted polyol process. The catalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), linear sweeping voltammetry, and chronoamperometry. The results show that the Pd and PdSn nanoparticles, which are uniformly dispersed on carbon, are 2–10 nm in diameters. All Pd/C and PdSn/C catalysts display the characteristic diffraction peaks of a Pd face-centered cubic (fcc) crystal structure. It is found that the addition of Sn to Pd can increase the lattice parameter of Pd (fcc) crystal. The PdSn/C catalysts have higher electrocatalytic activity for formic acid oxidation than a comparative Pd/C catalyst and show great potential as less expensive electrocatalyst for formic acid electrooxidation in DFAFCs.