Huaneng Su

Three dimensional palladium nanoflowers with enhanced electrocatalytic activity towards the anodic oxidation of formic acid

Three-dimensional palladium nanoflowers (Pd-NF) composed of ultrathin Pd nanosheets were synthesized by a solvothermal approach. The Pd-NF catalyst shows 6.6- and 5.5-fold enhancements in mass activity and surface activity compared to normal palladium nanoparticles (Pd-NP) in the electro-oxidation of formic acid.

Overview of Membrane Electrode Assembly Preparation Methods for Solid Polymer Electrolyte Electrolyzer

© 2012 Bladergroen et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Overview of Membrane Electrode Assembly Preparation Methods for Solid Polymer Electrolyte Electrolyzer

Enhanced electro-oxidation of formic acid by a PdPt bimetallic catalyst on a CeO2-modified carbon support

PdPt bimetallic catalysts that employ CeO2-modified carbon black as a support have been prepared using an organic colloidal method. PdPt/CeO2-C shows excellent performance toward the anodic oxidation of formic acid. The effects of varying both Pd to Pt ratio and CeO2 content have been investigated. The optimal Pd to Pt atomic ratio is 15, indicating that addition of small amounts of Pt can significantly enhance the activity of the catalyst. When the CeO2 content in the catalyst reaches as high as ∼15 wt.%, the catalyst shows the maximum activity. Adding CeO2 not only enhances the catalytic activity of the material, but may also change the mechanism of its catalysis of the anodic oxidation of formic acid. Pd15Pt1/15CeO2-C exhibited 60% higher activity than Pd/C, and had a negative shift in onset potential of more than 0.1 V. Based on characterization by X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and transmission electron microscopy, the interactions between the components are revealed and discussed in detail.

High-Performance and Durable Membrane Electrode Assemblies for High-Temperature Polymer Electrolyte Membrane Fuel Cells

Membrane electrode assemblies (MEAs) with gas diffusion electrodes (GDEs) fabricated by various catalyst layer (CL) deposit technologies were investigated for the application of high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC). The physical properties of the GDEs were characterized by scanning electron microscopy (SEM) and pore size distribution. The electrochemical properties were evaluated and analyzed by polarization curve, Tafel equation, electrochemistry impedance spectroscopy (EIS), and cyclic voltammetry (CV). The results showed that the electrodes prepared by ultrasonic spraying and automatic catalyst spraying under irradiation (ACSUI) methods have superior CL structure and high electrochemistry activity, resulting in high fuel cell performances. Durability tests revealed the feasibility of the electrodes for long-term HT-PEMFC operation.

The Effect of Gas Diffusion Layer PTFE Content on The Performance of High Temperature Proton Exchange Membrane Fuel Cell

Gas diffusion layer (GDL) with different polytetrafluoroethylene (PTFE) contents in the carbon substrate and the micro-porous layer (MPL) were investigated for the application in poly(2,5benzimidazole) (ABPBI)-based high temperature polymer electrolyte membrane fuel cell (HTPEMFC). The physical properties of the GDLs were characterized by scanning electron microscopy (SEM) and pore size distribution. The electrochemical properties of the single cell based on these GDLs were evaluated and analyzed by I-V curve and electrochemistry impedance spectroscopy (EIS). The results showed the use of a minimal quantity of PTFE in the carbon substrate (~15 wt%) and the MPL (~5-10 wt%) are suggested for both good mechanical properties of the GDLs and the good fuel cell performance.

Advances in HT-PEMFC MEAs

PEM (polymer electrolyte membrane) technology has been used in low-temperature fuel cells and high-temperature fuel cells, as well as water electrolyzers, for many years. Such electrochemical devices are of great interest and importance in the establishment of the so-called Hydrogen Economy . Advancement in polybenzimidazole (PBI)-based high-temperature proton exchange membrane fuel cells (HT-PEMFCs), specifically for stationary applications, has been achieved through systematic optimization of its components. Membrane electrode assembly (MEA) is the heart of an HT-PEMFC, and the fabrication of MEA is a key step for “real” HT-PEMFC applications. A series of studies on developing high-performance MEAs for PBI or ABPBI-based high-temperature fuel cells (120–180°C) are presented in this chapter. Some critical points and perspectives on developing high-performance MEAs are also summarized.

HT-PEMFC Modeling and Design

Modeling and simulation studies of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are important in order to better understand the operational behavior of the fuel cell and its performance and lifetime. These models play important roles in the understanding and prediction of HT-PEMFC performance and durability by analyzing various crucial parameters such as species concentrations, local current densities, temperature gradients, and pressure distributions within the fuel cell. These fuel cell modeling studies are often performed at the single cell level or stack level based on specific requirements and it may be either steady-state or dynamic using isothermal or nonisothermal models. The details of the modeling and simulation studies of HT-PEMFC at fuel cell level and stack level models including thermal management and electrochemical models are discussed in this chapter.

Catalysts for High-Temperature Polymer Electrolyte Membrane Fuel Cells

Increasing the temperature of polymer electrolyte membrane fuel cells (PEMFCs) implies advantages and disadvantages in terms of material cost, performance, and degradation. Platinum (Pt) is the best catalytic material for high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) electrodes, owing to the possibility it affords of minimizing CO poisoning with temperature enhancement. Nevertheless, it involves an increase in overall cost, mainly due to the larger platinum loadings used (when compared to Pt loadings for low-temperature polymer electrolyte membrane fuel cells). On the other hand, cathodic electrocatalysts still require that the kinetics of the sluggish oxygen reduction reaction be improved. Another disadvantage associated with the use of anodic and cathodic electrocatalysts is the corrosion of both carbon supports and catalytic nanoparticles, which is promoted by the increase in temperature. In this section, the most important factors affecting the performance of these materials are described and a brief description of the state of the art in the design and use of new materials in HT-PEMFCs is presented.

Stationary HT-PEMFC-Based Systems—Combined Heat and Power Generation

A combined heat and power (CHP) system for energy generation is the most suitable stationary application for fuel cells. High-temperature polymer electrolyte membrane fuel cell (HT-PEMFC)-based fuel cell CHP (FC-CHP) systems, owing to their high operating temperatures, have simpler layouts for auxiliary devices and can operate on reformate with relatively high CO content. The most suitable application of HT-PEMFC technology is in systems where utilization of heat is essential. This makes HT-PEMFC perfect for FC-CHP applications in which electrical energy and heat are produced in a cogenerated manner, enhancing the total efficiency of the overall system. Currently a few HT-PEMFC-based FC-CHP systems are being deployed worldwide and the results of preliminary validation are promising for the technology’s potential commercialization in the near future.