PEM Fuel Cell Catalyst Research Articles

Development of Highly Active Pt2Ni/C Catalyst for PEM Fuel Cell

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Development of Ultra-Low Pt Alloy Cathode Catalyst for PEM Fuel Cells

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Non-Precious Metal Oxygen-Reduction Catalysts for PEM Fuel Cells Based on N-Doped Ordered Porous Carbon

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STXM Characterization of PEM Fuel Cell Catalyst Layers

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Characterization of Pt Catalysts for PEM Fuel Cells

Carbon-supported platinum (Pt\\C) was combined with Ru metal or the transition metal oxide NiO, or both NiO and Co3O4 to obtain binary and ternary catalyst mixtures respectively. The electrochemical performance of these electrocatalysts for the hydrogen oxidation reaction was investigated using cyclic voltammetry in an in-house three electrode half cell. The physical characterization of the electrode catalysts was analyzed by scanning electron microscopy, energy dispersive X-ray analysis and Brunner-Emmet-Teller adsorption analysis. It was found that it did not matter if NiO was used on its own as an additive or in conjunction with Co3O4 in a mixture; the electrical activity improved notably when compared to pure Pt or Pt (40%)\\C used in the absence of NiO. The overall metal loading was 0.3 mg.cm−2 for both.

Magneli phase Ti n O2n − 1 as corrosion-resistant PEM fuel cell catalyst support

Magneli phase titanium suboxide, Ti n O2n − 1, with Brunauer–Emmett–Teller surface area up to 25 m2 g−1 was prepared using the heat treatment of titanium oxide (rutile) mixed with polyvinyl alcohol in ratios from 1:3 to 3:1. XRD patterns showed Ti4O7 as the major phase formed during the heat treatment process. The Ti n O2n − 1 showed excellent electrochemical stability in the potential range of −0.25 to 2.75 V vs. standard hydrogen electrode. The Ti n O2n − 1 was employed as a polymer electrolyte membrane fuel cell catalyst support to prepare 20 wt% platinum (Pt)/Ti n O2n − 1 catalyst. A fuel cell membrane electrode assembly was fabricated using the 20 wt% Pt/Ti n O2n − 1 catalyst, and its performance was evaluated using H2/O2 at 80 °C. A current density of 0.125 A cm−2 at 0.6 V was obtained at 80 °C.

Highly Durable Platinum-Cobalt Nanowires by Microwave Irradiation as Oxygen Reduction Catalyst for PEM Fuel Cell

Platinum-cobalt alloy nanowires (Pt-Co-NWs) synthesized by a facile, template free microwave-irradiation process are investigated as oxygen reduction reaction (ORR) catalysts for fuel cell applications. These materials displayed high ORR activity and exemplary stability through half cell testing in 0.1 M HClO4. Pt-Co-NWs are presented as potential replacements for traditional Pt/C cathode catalysts in fuel cell applications. © 2012 The Electrochemical Society. [DOI: 10.1149/2.018206esl] All rights reserved.

On the Determination of PEM Fuel Cell Catalyst Layer Resistance from Impedance Measurement in H2/N2 Cells

The commonly employed the H2/N2 cell impedance method for the determination of PEMFC catalyst layer ionic resistance often results in significant deviations from the predicted idealized homogeneous catalyst layer properties. In this study, the effect of the distribution of resistance and capacitance within the thickness of the CL is modeled to examine whether it explains the observed deviations. It is found that uniformly and non-uniformly distributed CLs show limiting real impedance (vertical line on Nyquist plot) at low frequency, as long as the impedance has no faradaic contribution. However, using this value of real impedance for obtaining the ionic resistance of the catalyst layer leads to significant errors if the system is non-uniformly distributed. It is shown that Nyquist plots with non-vertical mid-frequency regions, resembling experimentally measured H2/N2 cell response, can be generated with a “nested” transmission line circuit (agglomerate model) if there is a significant difference in resistance in different agglomerates.

Characterization of the PEM Fuel Cell Catalyst Layer Microstructure by Nonlinear Least-Squares Parameter Estimation

Models of polymer electrolyte membrane fuel cells (PEMFC) have become increasingly complex, using many parameters to define the behavior of species and the performance of the cell. A framework is presented here to couple an agglomerate electrode based, multi-dimensional, multi-physics mathematical model of membrane electrode assembly (MEA) model with an optimization-based nonlinear least-squares parameter estimation algorithm. The framework is used to estimate the micro-structural parameters of the catalyst layer such as agglomerate size. The results show that a set of data over a range of operating conditions can be accurately described by using a unique set of structural parameters that match experimental visualization of the catalyst layer. Extension of this methodology can be used to systematically estimate any model parameters in order to reduce uncertainty in model predictions.

Fabrication Process Simulation of a PEM Fuel Cell Catalyst Layer and Its Microscopic Structure Characteristics

The catalyst layers (CLs) in proton exchange membrane fuel cells (PEMFCs) are porous composites of complex microstructures of the building blocks, i.e., Pt nano-particles, carbonaceous substrates and Nafion ionomers. It is important to understand the factors that control the microstructure formation in the fabrication process. A coarse-grained molecular dynamics (CG-MD) method is employed to investigate the fabrication process of CLs, which depends on the type and amount of components and also the type of the dispersion medium (ethylene glycol, isopropanol or hexanol) used during ink preparation of the catalyst-coated membranes (CCMs). The dynamical behaviors of all the components are outlined and analyzed following the fabrication steps. In addition, the Pt nano-particle size distribution is evaluated and compared with the labor testing. Furthermore, the primary pore size distributions in the final formations of three cases are shown and compared with the experiments. The sizes of the reconstructed agglomerates are also considered on the effect of solvent polarity.

Nanocrystalline tungsten carbide (WC) synthesis/characterization and its possible application as a PEM fuel cell catalyst support

Nanocrystalline tungsten carbide (WC) with a high surface area and containing minimal free carbon was synthesized via a polymer route. Its physical properties, including solubility in acid solution, electronic conductivity, and thermal stability, were thoroughly studied at two elevated temperatures: 95 °C and 200 °C. Compared to commercially available WC, this in-house synthesized WC showed lower solubility in acidic media at 200 °C, higher electronic conductivity (comparable to that of carbon black), as well as higher thermal stability. However, this material exhibited low electrochemical stability in acidic media when subjected to potential cycling at potentials larger than 0.7 V vs. RHE, due to the electrooxidation of WC. The major product of WC electrooxidation is WO 3, which was confirmed by X-ray photon spectroscopy measurements. Pt was uniformly deposited on the high surface area WC to form a 20 wt% of Pt supported catalyst for the oxygen reduction reaction (ORR). The ORR mass activity was then obtained using the rotating disk electrode technique.

Electrocatalytic activity and durability of Pt/NbO 2 and Pt/Ti 4O 7 nanofibers for PEM fuel cell oxygen reduction reaction

In this paper, we report the synthesis of both NbO 2 and Ti 4O 7 nanofibers using an electrospinning technique in an effort to use metal oxides as a possible replacement for carbon as PEM fuel cell catalyst supports. The synthesized nanofibers are physically characterized using several methods including XRD, SEM, TEM, BET, ICP-MS as well as XPS. The thermal, chemical, and electrochemical stabilities as well as the electronic conductivities of these two supports are also evaluated in order to check their feasibility as catalyst supports in the temperature range of 95–200 °C. Two catalysts, 20-wt% Pt/NbO 2 and 20-wt% Pt/Ti 4O 7, are prepared and tested for both ORR mass activity and stability in acidic solution. XPS measurements of samples analyzed before and after the durability tests suggest the formation of electronically insulating surface oxides, which can be partially responsible for both low ORR mass activity and catalyst durability.

Electrodeposition of PEM fuel cell catalysts by the use of a hydrogen depolarized anode

Up to 30% of the expensive catalyst metal in conventional fuel cell catalysts is not utilized in fuel cells caused by an absence of contact to either the ion conducting, electron conducting or educt phase. This contact can be improved by in situ electrodeposition with a precursor layer which is mostly done in a galvanostatic mode in the literature. In this paper electrochemical deposition with a hydrogen depolarized anode is described and so a potentiostatic electrodeposition under the control of the working-electrode potential and dry working-electrode conditions is enabled. This potentiostatic electrodeposition with a hydrogen depolarized anode significantly increases the performance of the fuel cell.

Development of Ultra-Low Pt Alloy Cathode Catalyst for PEM Fuel Cells

Two approaches are described for the synthesis of ultra-low platinum loading catalysts for polymer electrolyte membrane fuel cell (PEMFC). The first approach is the synthesis of a hybrid cathode catalyst (HCC) which combines a non-platinum carbon based composite catalyst (CCC) with active catalytic sites for oxygen reduction reaction (ORR) as a support and highly active Pt/Pt-alloy catalysts. The activity of HCC is found to be 1.3 times higher than that of Pt/C in the platinum loading range of 0.1-0.4 mg cm-2, while it is 2.6 times that of Pt/C at platinum loading of 0.04 mg cm-2. The goal of our second strategy is the development of activated graphitic carbon (AGC) supported Pt3M1 (M=non-precious transition metal) catalyst (Pt3M1/AGC). The Pt3M1/AGC catalyst showed mass activity of 0.41 A mgPt-1 and specific activity of 1023 µA/cm2 at 0.9 ViR-free. Fuel cell performance evaluation under H2/air exhibited a high current density performance of 1.45 A at 0.56 ViR-free.

Pt Monolayer on Electrodeposited Pd Nanostructures-Advanced Cathode Catalysts for PEM Fuel Cells

The Pt monolayer-shell Pd nanowires/nanorods-core (PtML/PdNW(PdNR)) electrocatalysts, supported on carbon nanoparticles are notable for their very high activity and stable performance towards the oxygen reduction reaction (ORR). In the present work Pd nanostructures are electrochemically deposited on oxidized carbon (COX) surface and the impact of the deposition parameters on the deposits morphology is studied. The electrochemical deposition of Pd nanowires is demonstrated for the first time, and a viable mechanism for the growth of Pd nanostructures is proposed. The one-dimensional growth of the Pd nanowires is ascribed to the hydrogen-underpotential-mediated layer-by-layer deposition of Pd. In addition, the surface structure of deposited nanowires is composed predominantly of {111}-oriented facets that facilitate the enhanced ORR activity and stability of the PtML/PdNW/COX electrocatalysts. The Pt mass and specific activities of these electrocatalysts, as well as their stable performance under potential cycling conditions, are significantly higher than those of the commercial Pt/C electrocatalysts, and highlight their great potential for resolving the remaining obstacles to commercializing PEMFCs.

Transient Platinum Oxide Formation and Oxygen Reduction on Carbon-Supported Platinum and Platinum-Alloy Electrocatalysts

Chronoamperometry studies at a fixed potential of 0.9V vs. the reversible hydrogen electrode (RHE) have been performed on three PEM fuel cell catalysts (50 wt.% Pt/C, 30 wt. % PtM1/C and 30 wt. % PtM2/C) on both rotating disk electrodes (RDEs) and membrane electrode assemblies (MEAs), in order to investigate similarities and differences between Pt and Pt-alloy catalysts for transient behavior of the oxygen reduction reaction (ORR). Similar trends of reversible activity degradation were shown for both RDEs and MEAs. Compared to the baseline Pt/C catalyst, alloy catalysts under potential hold were found to have higher oxide coverage and faster oxide-growth rate, with the latter related to their faster transient ORR activity degradation rate. In addition, PtM1/C showed a higher ORR activity than PtM2/C in MEA tests, while the opposite trend was found in RDE tests, which could be attributed to their different transient stability under potential hold.

On the Determination of PEM Fuel Cell Catalyst Layer Resistance from Impedance Measurement in H2/N2 Cells

Impedance measurements of H2/N2 cell for the determination of PEMFC catalyst layer (CL) resistance can exhibit significant deviation from those predicted assuming homogeneous CL structure with uniform resistance and capacitance. Predictions from model with homogeneous structure but distributed resistance and/or capacitance shows deviation from the ideal mid-frequency response (45o line) but expected low-frequency response (vertical line). A distributed model considering agglomerate-type structure shows deviation from ideal mid-frequency response ((45o line) as well as from ideal vertical-line like response at experimentally employed frequencies although a vertical-line response is predicted at frequencies significantly lower than typically accessible in experiments.

Pt Monolayer on Electrodeposited Pd Nanostructures-Advanced Cathode Catalysts for PEM Fuel Cells

not Available.

Development of Ultra-Low Pt Alloy Cathode Catalyst for PEM Fuel Cells

not Available.

On the Determination of PEM Fuel Cell Catalyst Layer Resistance from Impedance Measurement in H2/N2 Cells

not Available.