Multi-Segment Foam Flow Field in Ambient Pressure Polymer Exchange Membrane Fuel Cell

In order to produce low-cost flow field plates for polymer electrolyte membrane fuel cells, we used nickel foam in this study rather than conventional flow field. Nickel foam has high electron conductivity, thermal conductivity, and mechanical strength. Electrochemical impedance spectrum analysis is carried out to evidence the use on flow field plates of nickel foam. From the impedance fitting results, the nickel foam cases showed the lower contact resistance than the serpentine. However, such plates have poor performance at low temperatures and ambient pressure. In order to overcome this, a multi-segment foam flow field is designed in this study. This increased the performance of the polarization curve by 70% from 162 to 275.5 mw cm-2 than the original nickel foam design. Also, the mass transfer resistance was reduced, and the Warburg impedance value of the operation voltage decreased by 0.4 V. The numerical analysis results demonstrate that increased segment numbers can increase the performance of the multi-segment foam flow field

Optimisation of electrophoretic deposition parameters for gas diffusion electrodes in high temperature polymer electrolyte membrane fuel cells

Electrophoretic deposition (EPD) method was used to fabricate gas diffusion electrodes (GDEs) for high temperature polymer electrolyte membrane fuel cells (HT PEMFC). Parameters related to the catalyst suspension and the EPD process were studied. Optimum suspension conditions are obtained when the catalyst particles are coated with Nafion® ionomer and the pH is adjusted to an alkaline range of about 8 e10. These suspensions yield good stability with sufficient conductivity to form highly porous catalyst layers on top of the gas diffusion layers (GDLs). GDEs were fabricated by applying various electric field strengths of which 100 V cm-1 yields the best membrane electrode assembly (MEA) performance. Compared to an MEA fabricated by the traditional hand sprayed (HS) method, the EPD MEA shows superior performance with a peak power increase of about 73% at similar platinum (Pt) loadings. Electrochemical Impedance Spectroscopy (EIS) analysis shows lower charge transfer resistance for the MEA fabricated via the EPD method compared to the HS MEA. The EPD GDE exhibits a greater total pore area (22.46 m2 g-1) compared to the HS GDE (13.43 m2 g-1) as well as better dispersion of the Pt particles within the catalyst layer (CL).Web of Scienc

Fuel cell performances at optimized Nafion and Ru85Se15 loadings in cathode catalyst layer

Fujian Key Laboratory of Advanced Materials, China [2006L2003]; Xiamen University; Yuan Ze UniversityThe citric acid treated carbon supported Ru85Se15 catalysts are synthesized by microwave assisted polyol method at the optimal solution pH = 7. The catalyst coated membrane method with ultrasonic-spray technique is employed to prepare electrodes without hot press step. The cell performances with different Nation contents and Ru loads in the cathode catalyst layer are systematically examined in both H-2/air and H-2/O-2 fuel cells at 65 degrees C under ambient pressure. The surface morphologies of membrane electrode assemblies and the interfacial characteristics of single cells are studied using scanning electron microscopy and electrochemical impedance spectroscopy, respectively. The Nation content is optimized to be 33% when the catalyst loadings are lower than 0.8 and 0.6 mg Ru cm(-2) in the H-2/air and H-2/O-2 fuel cells, respectively, but reduced to 20% at the higher Ru loads. The maximum peak power densities of 190 mW cm(-2) at 620 mA cm(-2) and 400 mW cm(-2) at 1430 mA cm(-2) are achieved in the H-2/air and H-2/O-2 fuel cells, respectively, with 0.27 mg Ru cm(-2) and 33% Nafion. The best catalyst utilizations are obtained at 0.14 mg Ru cm(-2) with 33% Nation, resulting in the maximum peak power densities per unit mass Ru of 917 and 2460 mW mg(-1) in the H-2/air and H-2/O-2 fuel cells, respectively. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved

Fuel cell performances at optimized Nafion and Ru85Se 15 loadings in cathode catalyst layer

The citric acid treated carbon supported Ru85Se15 catalysts are synthesized by microwave assisted polyol method at the optimal solution pH = 7. The catalyst coated membrane method with ultrasonic-spray technique is employed to prepare electrodes without hot press step. The cell performances with different Nafion contents and Ru loads in the cathode catalyst layer are systematically examined in both H2/air and H 2/O2 fuel cells at 65 掳C under ambient pressure. The surface morphologies of membrane electrode assemblies and the interfacial characteristics of single cells are studied using scanning electron microscopy and electrochemical impedance spectroscopy, respectively. The Nafion content is optimized to be 33% when the catalyst loadings are lower than 0.8 and 0.6 mg Ru cm-2 in the H2/air and H2/O2 fuel cells, respectively, but reduced to 20% at the higher Ru loads. The maximum peak power densities of 190 mW cm-2 at 620 mA cm-2 and 400 mW cm-2 at 1430 mA cm-2 are achieved in the H2/air and H2/O2 fuel cells, respectively, with 0.27 mg Ru cm-2 and 33% Nafion. The best catalyst utilizations are obtained at 0.14 mg Ru cm-2 with 33% Nafion, resulting in the maximum peak power densities per unit mass Ru of 917 and 2460 mW mg-1 in the H 2/air and H2/O2 fuel cells, respectively. 漏 2011 Published by Elsevier B.V. All rights reserved

Microwave assisted synthesis of high performance Ru85Se15/MWCNTs cathode catalysts for PEM fuel cell applications

Fujian Key Laboratory of Advanced Materials, China [2006L2003]; Xiamen University; Yuan Ze UniversityThe Ru85Se15 nanoparticles supported on commercial Vulcan XC-72R or multi-walled carbon nanotubes (MWCNTs) were synthesized by microwave assisted polyol method with different solution pH. The Ru85Se15 nanoparticles on citric acid (CA)-treated supports prepared at pH = 7 exhibited the most uniform particle distribution, higher degree of graphitization on supports, and four-electron ORR mechanism. Using lower loading of 0.138 mg Ru cm(-2), the maximum power densities (P-max) for the Ru85Se15/CA-MWCNTs and Ru85Se15/CA-XC72R were 380 mW cm(-2) at 1430 mA cm(-2) and 336 mW cm(-2) at 1230 mA cm(-2), respectively, with oxygen, while 166 mW cm(-2) at 710 mA cm(-2) and 126 mW cm(-2) at 510 mA cm(-2), respectively, with air. The P-max of 103 mW cm(-2) with air for the Ru85Se15/CA-MWCNTs could be retained (38% loss), while 46 mW cm(-2) for Ru85Se15/CA-XC72R (64% loss) upon 6000 cycles. The four-electron ORR mechanism and highly graphitized MWCNTs might be responsible for the high performance and durability of Ru85Se15/CA-MWCNTs. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

Investigation of Different Carbon Materials with Different Coating Methods as Micro Porous Layer for Proton Exchange Membrane Fuel Cells

Abstract: In this work, two types of carbon - Vulcan XC-72R, and vapor-grown carbon fiber (VGCF, 7μm in length and 100 nm in diameter) were investigated as materials composing a micro porous layer (MPL). These carbon materials were either sprayed or doctor bladed on commercial carbon paper (GDS 340, CeTech Co., Ltd., Taiwan) to form an MPL with various carbon loadings and various polytetrafluoroethene (PTFE) contain ratio. All of the home-made GDLs were assembly with commercial catalyst coated membranes (CCMs, General Optics Corp., Taiwan) for fuel cell performance test. All of the membrane electrode assembly (MEA) samples were investigated by the polarization curve and Electrochemical Impedance Spectroscopy (EIS)

Degradation analyses of Ru85Se15 catalyst layer in proton exchange membrane fuel cells

Accelerated degradation tests (ADTs) for the H2/air single cell are carried out at 65掳C and ambient pressure by cycling the cell between 0 and 200 mA cm-2 up to 6000 cycles. Membrane electrode assemblies (MEAs) are prepared using the Nafion 212 membrane and the carbon supported platinum as an anode catalyst, as well as the carbon supported Ru 85Se15 as a cathode catalyst prepared with five selected Nafion contents and Ru loads to represent the optimized (33% Nafion and 0.27 mg Ru cm-2), overloaded (43% Nafion and 0.61 mg Ru cm-2) and underloaded (20% Nafion and 0.14 mg Ru cm-2) conditions. The lowest cell performance loss of 44% in terms of peak power density is achieved with 33% Nafion and 0.27 mg Ru cm-2. Very severe losses of 80% and 82% are found for 20% and 43% Nafion contents, respectively, while relatively moderate losses of 57% and 64% for 0.14 and 0.61 mg Ru cm-2, respectively. Dissolution and migration of Se/Ru and corrosion of carbon support from the catalyst, together with the shrinkage and release of sulfonic acid from the membrane are identified and correlated to decayed cell performances. 漏 2012 Elsevier B.V

A comparative study of pyrolyzed and doped cobalt-polypyrrole eletrocatalysts for oxygen reduction reaction

Fujian Key Laboratory of Advanced Materials, China [2006L2003]; Xiamen University; Yuan Ze UniversityThe pyrolyzed carbon supported cobalt polypyrrole (Co-PPy/C) catalysts were prepared without or with three selected dopants, namely, sodium dodecylbezene sulfonate (DBSNa), sodium paratoluene sulfonate (TSNa) and sodium bezene sulfonate (BSNa), respectively, through chemical oxidation with ferric chloride as an oxidant. The structure, surface and electrochemical properties of the obtained catalysts were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmitt-Teller (BET) analysis, cyclic voltammetry, rotating disc electrode technique and Raman spectroscopy. The introduction of dopants increased the surface concentrations of nitrogen and cobalt which would provide more active sites for oxygen reduction reaction (ORR), and enhanced the graphitization degree of carbon support which would improve the electron conductivity. The electron numbers of ORR for the non-doped and doped Co-PPy/C were evaluated to be 2.7-3.1, respectively. The pyrolyzed BSNa-doped Co-PPy/C exhibited the best electrocatalytic activity toward ORR due to its higher surface areas, larger amounts of micropores, as well as relatively higher nitrogen and cobalt contents. (C) 2011 Elsevier B.V. All rights reserved

Electrocatalytic Activities of Ru85Se15 Catalysts Prepared by Microwave Method

Conference Name:11th Polymer Electrolyte Fuel Cell Symposium (PEFC) Under the Auspices of the 220th Meeting of the ECS. Conference Address: Boston, MA. Time:OCT, 2011.The Vulcan carbon black (XC-72R) supported or multiwalled carbon nanotubes (MWCNTs) supported Ru85Se15 nonoparticles were synthesized by microwave assisted method at different pH. The XC-72R and MWCNTs supports were functionalized using citric acid treatment. Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and rotating disk electrode (RDE) techniques were applied for characterizations of the obtained catalysts. The results revealed that the smaller sized Ru85Se15 nanoparticles were better dispersed on citric acid treated XC-72R or MWCNTs supports prepared at pH=7, and the Ru85Se15 catalysts possessed high electrocatalytic activities for oxygen reduction reaction in acidic solutions both in the absence and presence of methanol