Platinum and Palladium Monolayer Electrocatalysts for Formic Acid Oxidation

Topics in Catalysis - The direct formic acid fuel cell holds great promise as a next generation portable power source. Here we report an experimental study on Pt and Pd monolayer (Pt* and Pd*) atop...     

低温燃料电池阳极非铂电催化剂研究进展

介绍了低温燃料电池的特点及其阳极铂基催化剂目前存在的主要问题,综述了低温燃料电池阳极非铂催化剂的研究概况,着重介绍了在提高非铂催化剂的电催化活性和抗CO中毒能力等方面的研究进展。     

用磷钼酸修饰甲醇燃料电池的铂电极

近年来以杂多化合物为基础的催化体系受到广泛的关注.为了研究杂多酸与铂电极对甲醇电催化氧化的协同效应,通过循环伏安扫描法制备了磷钼酸（H3PMo12O40）修饰铂电极.通过循环伏安和计时电流法研究了该修饰电极对甲醇氧化的电催化活性和抗中间产物的毒化作用,并比较了该修饰电极与其单酸盐（Na2MoO4）修饰铂电极的性能,测试结果表明：磷钼酸修饰铂电极能够提高对甲醇氧化反应的催化活性,基本上同其单酸盐Na2MoO4修饰铂电极的催化活性相当,并且这种促进作用主要是由Mo原子价态变化引起的.同时计时电流曲线测试结果表明,该修饰电极具有一定的抗毒化作用,但不如钼酸钠好.     

Nanostructured Carbons as Platinum Catalyst Supports for Proton Exchange Membrane Fuel Cell Electrodes

To improve mass transport in the catalytic layers of proton exchange membrane fuel cells, the usual Pt catalyst support (carbon blacks) can be advantageously replaced by carbon aerogels or xerogels. The pore texture of such materials can indeed be tailored, which enables choosing an adequate pore texture minimizing diffusional limitations within the catalytic layers.     

CO Desorption Rate Dependence on CO Partial Pressure over Platinum Fuel Cell Catalysts

Carbon monoxide adsorption on high area platinum fuel cell catalysts was investigated. Isotopic exchange experiments were performed to determine the exchange rate (k) of CO under different partial pressures of CO (p_CO) in argon. A linear dependence of ln(k) with ln(p_CO) was observed. This pressure dependence of the rate of exchange is explained by considering a change in surface coverage of CO with different CO pressures and a subsequent reduction in the CO binding energy as demonstrated by Density Functional Theory (DFT) calculations. High Pressure Scanning Tunneling Microscopy (HP STM) studies on the Pt(111) surface have also displayed a pressure dependency of the coverage consistent with this data. The relevance of these observations to the Polymer Electrolyte Membrane Fuel Cell (PEMFC) anode reaction is discussed.     

燃料电池

<正> 地球上能源主要来自煤、石油及天然气等燃料。这些物质在地下的贮存量是有限的,它们迟早会被用完。因此检查这些物质是否已经物尽其用,显然是极其重要并有深远意义的。利用烃类燃料能量的方法,不外是把它在空气中燃烧产生的热,用来产生高压蒸汽,推动涡轮机作功,或者把它在内燃机中燃烧,直接推动机器作功或发电。这种利用都会产生大量的烟雾、臭氧、二氧化氮等污染空气,并可提高空气中二氧化碳的浓度。另外,蒸汽机、内燃机等热机的能量利用效率要受卡诺效率的限制,燃料直接燃烧的热能有60%以上没有利用,若是使燃烧反应在燃料电池中来实现,则反应的热效应可部分或全部转变为电功,而且电池中能量转换的效率几乎都超过热机效率的一倍以上。从节约能源观点来     

Enhanced Oxygen Reduction Activity of IrCu Core Platinum Monolayer Shell Nano-electrocatalysts

Designing novel cathode materials for a proton exchange membrane fuel cell with high activity for the oxygen reduction reaction, low Pt loading, and enhanced long-term stability is imperative for its sustainability. To date, Pt monolayer based electrocatalysts deposited on a metallic core substrate have shown promising possibilities. In this study, we synthesized bimetallic IrCu nanoparticles and used them as a core for Pt monolayer electrocatalysts. It was found that the de-alloyed IrCu nanoparticle surfaces increased both the mass and specific activities of the resulting Pt monolayer catalyst. In addition, we demonstrated that Pt monolayer electrocatalysts with a de-alloyed IrCu core have a better stability than those using a non-dealloyed core based on a 5,000 potential cycling test. These data describe a new simple synthesis of a high-performance catalyst suitable for practical applications.     

不同载体电催化剂对氢氧燃料电池的影响

以氢氧化物交换膜带燃料电池的制备原理为依据,基于标准三电极体系,采用氮掺杂法、水煮还原法与氩气微波处理法,针对经过直接处理后的催化剂进行电化学性能测试。实验结果显示,采用氮掺杂与氩气微波两种方法处理后的电催化剂性能得到明显提升,有助于进一步提升催化剂的利用率。     

Influence of Pyridine‐Polybenzimidazole Film Thickness of Carbon Nanotube Supported Platinum on Fuel Cell Applications

Pyridine‐polybenzimidazole (PyPBI) films of different thickness (∼1.0–2.4 nm) are wrapped on the surfaces of multi‐walled carbon nanotubes (CNTs). To prepare Pt on PyPBI/CNT (Pt‐PyPBI/CNT) catalysts, Pt⁴⁺ ions are immobilized on these PyPBI wrapped CNTs (PyPBI/CNTs) via Lewis acid‐base coordination between Pt⁴⁺ and :N‐ of imidazole groups, followed by reducing Pt⁴⁺ to Pt nanoparticles. The influence of PyPBI film thickness on the Pt particle size, loading and electrochemical surface area, respectively, of Pt‐PyPBI/CNTs is investigated. Fuel cell performances of the PBI/H₃PO₄ based membrane electrode assemblies (MEAs) prepared from these Pt‐PyPBI/CNT catalysts are also evaluated at 160 °C with unhumidified H₂/O₂ gases. Among the catalysts, the Pt‐PyPBI/CNT catalyst with a PyPBI film thickness of ∼1.6 nm (which is around half of the Pt particle size), a Pt loading of ∼44 wt.%, and a Pt particle size of ∼3.3 nm exhibits the best fuel cell performance.     

Nanostructured Anode Pt–Ru Electrocatalysts for Direct Methanol Fuel Cells

A novel aerosol-assisted approach for the synthesis of a nanostructured bimetallic Pt–Ru network is demonstrated in which monodisperse silica is used as a template. This approach allows for simplified synthesis and short synthesis times. The nanostructured Pt–Ru network is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface area measurements. Cyclic voltammetry (CV) shows enhanced electrocatalytic currents which we believe is due to improved mass transfer as a result of the nanostructured morphology.     

New Electrocatalysts for Fuel Cells from Model Surfaces to Commercial Catalysts

In the last decade of the 20th century, we have witnessed a resurgence of interest in fuel cell technology, a technology whose basic principles were demonstrated in the mid-19th century. One of the drivers of this resurgence is the use of hydrogen as a transportation fuel, and the certification by the California Air Resources Board (CARB) of a hydrogen - air fuel cell powered vehicle as a "zero emission vehicle" or ZEV. Another driver is the simplicity of construction and assembly of fuel cell stacks when a polymer membrane is used as the electrolyte versus the more conventional aqueous electrolyte. The polymer electrolyte membrane (PEM) fuel cell offers the promise of substantially lower cost for the cell hardware. Unfortunately, two of the fundamental catalytic limitations that have plagued fuel cells for more than a century still remain: 1.) it is difficult to use any fuel other than highly purified hydrogen; 2.) there has been no cost-effective replacement of Pt as the electrocatalyst. Fortunately, there are signs that help is on the way, particularly with respect to the development of new electrocatalysts for electrooxidation of impure hydrogen, e.g. CO-contaminated, or even syngas. In this article, we describe some of these developments, which have come from over two decades of basic research on electrocatalysis.     

Instability of Supported Platinum Nanoparticles in Low-Temperature Fuel Cells

This paper discusses the mechanisms of surface area loss of supported platinum (Pt) electrocatalysts in low-temperature fuel cells. It is argued that submonolayer dissolution of Pt nanoparticles governs the surface area loss at high voltages by increasing the loss of Pt from carbon and coarsening of Pt nanoparticles on carbon. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

XPS Structural Studies of Nano-composite Non-platinum Electrocatalysts for Polymer Electrolyte Fuel Cells

The chemical structure of non-platinum electrocatalysts obtained from cobalt porphyrins (CoTMPP or CoTPP) by pyrolysis is investigated by X-ray Photoelectron Spectroscopy (XPS). The catalysts represent highly dispersed, self-supported nano-composites that demonstrate electrocatalytic performance for oxygen reduction and practically no activity in methanol electro-oxidation. High-resolution Co2p, C1s, N1s and O1s XPS spectra acquired from precursors and electrocatalysts pyrolyzed at various experimental conditions were curve-fit using (a) individual peaks of constrained width and shape as well as (b) experimentally obtained photopeaks from the precursor with additional peaks required for a complete curve fit. Principal Component Analysis (PCA) applied to quantitative results from the curve-fits of both types of spectra facilitates visualization and identification of the chemical species that are formed or destroyed, and simplifies evaluation of critical correlations. As a result of these studies it is established that the catalyst is a nano-composite of highly dispersed pyropolymer with some remaining N _x -centers inserted into a graphite-like matrix. Approximately 50% of the metal is distributed as Co²⁺, associated with N₄-centers. The remaining cobalt is present in crystallites of metallic Co. A thin layer of CoO coats these metallic cobalt phases. The developed methodology, described herein, combines model curve-fits and principal component analysis (PCA), resulting in a quantitative and unambiguous understanding of the chemical composition and structure of complex electrocatalysts.     

Membrane Electrode Assembly with Ultra Low Platinum Loading for Cathode Electrode of PEM Fuel Cell by Using Sputter Deposition

Cathode electrodes of proton exchange membrane fuel cells were fabricated by using Pt sputter deposition to increase the gravimetric power density (W mg_Pt⁻¹) with reduced Pt loading. Ultra low Pt‐based electrodes having Pt loading in between 0.0011 and 0.06 mg_Pt cm⁻² were prepared by a radio frequency (RF) sputter deposition method on the surface of a non‐catalyzed gas diffusion layer (GDL) substrate by changing the sputtering time (20, 90, 180, 1050 s). The effect of cathode Pt loading on the performance of membrane electrode assembly were investigated using polarization curve, impedance, H₂ crossover and cyclic voltammetry techniques. The effect of backpressure on PEMFC performance was also investigated. Sputter1050 (0.06 mg_Pt cm⁻²) exhibited the best power density at 80 °C cell temperature and without backpressure for H₂/O₂, 100 %RH (297 mW cm⁻² and 5 W mg_Pt⁻¹ at 0.6 V). On the other hand sputter90 (0.005 mg_Pt cm⁻²) showed the peak gravimetric power density (15 W mg_Pt⁻¹ and 75 mW cm⁻² at 0.6 V). The Pt utilization efficiency increased as the Pt loading decreased. Sputter20 and sputter90 electrodes yielded insufficient electrochemical surface area (ECSA), higher charge transfer and ohmic resistance, but sputter180 and sputter1050 yielded sufficient ECSA and lower charge transfer and ohmic resistance.     

Pt Alloy Electrocatalysts for Proton Exchange Membrane Fuel Cells: A Review

Both the CO poisoning problem on the anode and the slow oxygen reduction reaction kinetics on the cathode lead to significantly decreased output power and energy utilization efficiency and remain main obstacles hindering commercialization of proton-exchange membrane fuel cells (PEMFCs). A promising means to mitigate CO poisoning and to improve the oxidation reduction reaction (ORR) activity is through the use of platinum alloy catalysts. This article reviews recent developments in Pt alloy catalyst utilization and addresses activity comparisons and the relationship between activity and structure characteristics. The mechanisms for improved CO-tolerance and ORR activity are also discussed. Finally, theoretical studies on Pt alloy catalysts are discussed briefly.     

乙烷质子交换膜燃料电池的研究

研究了以乙烷作为燃料、全氟磺酸高分子膜(Nafion膜)作为质子交换膜、Pt或Pt-Ru作为电极催化剂主要组分、并通过掺杂Nafion膜作为电极内的离子导体构成的燃料电池电化学性能.研究了两种电极催化剂:Pt与Pt-Ru复合催化剂的制备及构成的单电池在不同温度及运行时间下的电化学性能.温度增加,电池性能变好;运行时间增加,电池性能下降,在相同的温度与运行时间下,Pt-Ru复合催化剂构成的电池比Pt催化剂构成的电池极化小.通过分析电极反应产物,探讨了乙烷电极及电池的反应机理.结构为C2H6,( Pt-Ru+膜材料复合阳极)/Nafion膜/(Pt+膜材料复合阴极),O2 的质子交换膜燃料电池,在150℃时,电池的最大输出电流和功率密度分别高达70 mA·cm-2和22 mW·cm-2.     

燃料电池的发展趋势

介绍了燃料电池的工作原理、优缺点;同时以燃料电池应用为背景,综述不同类型的燃料电池如车用质子交换膜燃料电池、航天飞行器用再生燃料电池、小型便携式产品用直接甲醇燃料电池、中小型电站用固体氧化物燃料电池(SOFC)、微生物燃料电池(MFC)的技术发展现状与研究热点,并指出了未来燃料电池的发展趋势.     

固态质子导体型燃料电池反应器

将固态质子导体型燃料电池作为新型反应器用于合成化学品,产物选择性高,能耗低,可以实现电能与化学品共生.通过对反应器操作参数的调变,可以获得预期的化学产品及相应的电化学特性.本工作综述了固态质子导体型燃料电池反应器在简单无机物加氢、具有不饱和键脂肪族和芳香族化职物加氢、醇脱氢以及烷烃脱氢等反应中的应用.随着对该反应过程认...     

燃料电池技术及其国内外研究概况

本文介绍了燃料电池的工作原理、发展历史以及特点,简述了燃料电池主要的分类情况。同时对国内外燃料电池的研究发展状况进行了概述。     

SOFCo Planar Solid Oxide Fuel Cell

SOFCo-EFS Holdings LLC has developed a multi-layer, planar solid oxide fuel cell (SOFC) stack that has the potential to provide superior performance and reliability at reduced costs. Our approach combines state-of-the-art SOFC materials with the manufacturing technology and infrastructure established for multi-layer ceramic (MLC) packages for the microelectronics industry. With the proper selection of SOFC materials, implementation of MLC fabrication methods offers unique designs for stacks. Over the past two years, substantial progress has been made in the design and manufacturing development of our second-generation stack. Effective stack and manifold seals have been developed. Cell performance has been improved and relatively low non-cell contributions to stack resistance have been achieved. Stack development has been facilitated through the implementation of two key test methods: (1) a 10-cm single-cell test to bridge the gap in performance data obtained from button cell tests (used for cell R&D) and stack tests; and (2) a novel instrumented short stack (<5 cells) that allows for effective isolation of individual contributions to stack resistance. As a result of progress made to date, a clear pathway for improving stack performance has been established, thereby building confidence that commercial stack performance targets will be reached.