Fuel cells, hydrogen and energy supply in Australia

Australia is unique in terms of its geography, population distribution, and energy sources. It has an abundance of fossil fuel in the form of coal, natural gas, coal seam methane (CSM), oil, and a variety renewable energy sources that are under development. Unfortunately, most of the natural gas is located so far away from the main centres of population that it is more economic to ship the energy as LNG to neighboring countries. Electricity generation is the largest consumer of energy in Australia and accounts for around 50% of greenhouse gas emissions as 84% of electricity is produced from coal. Unless these emissions are curbed, there is a risk of increasing temperatures throughout the country and associated climatic instability. To address this, research is underway to develop coal gasification and processes for the capture and sequestration Of CO2. Alternative transport fuels such as biodiesel are being introduced to help reduce emissions from vehicles. The future role of hydrogen is being addressed in a national study commissioned this year by the federal government. Work at the University of Queensland is also addressing full-cycle analysis of hydrogen production, transport, storage, and utilization for both stationary and transport applications. There is a modest but growing amount of university research in fuel cells in Australia, and an increasing interest from industry. Ceramic Fuel Cells Ltd. (CFCL) has a leading position in planar solid oxide fuel cells (SOFCs) technology, which is being developed for a variety of applications, and next year Perth in Western Australia is hosting a trial of buses powered by proton-exchange fuel cells. (C) 2004 Elsevier B.V. All rights reserved.

Synthesis and characterization of nano-hetero-structured dy doped CeO2 solid electrolytes using a combination of spark plasma sintering and conventional sintering

Doped ceria (CeO2) compounds are fluorite-type oxides that show oxide ionic conductivity higher than yttria-stabilized zirconia in oxidizing atmosphere. As a consequence of this, considerable interest has been shown in application of these materials for low (500 degrees-650 degrees C) temperature operation of solid oxide fuel cells (SOFCs). To improve the conductivity in dysprosium (Dy) doped CeO2, nano-size round shape particles were prepared using a coprecipitation method. The dense sintered bodies with small grain sizes (< 300 nm) were fabricated using a combined process of spark plasma sintering (SPS) and conventional sintering (CS). Dy-doped CeO2 sintered body with large grains (1.1 mu m) had large micro-domains. The conductivity in the sintered body was low (-3.2 S/cm at 500 degrees C). On the other hand, the conductivity in the specimens obtained by the combined process was considerably improved. The micro-domain size in the grain was minimized using the present process. It is concluded that the enhancement of conductivity in dense specimens produced by the combined process (SPS+CS) is attributable to the microstructural changes within the grains.

Design of high quality doped CeO2 solid electrolytes with nanohetero structure

Doped ceria (CeO2) compounds are fluorite related oxides which show oxide ionic conductivity higher than yttria-stabilized zirconia in oxidizing atmosphere. As a consequence of this, a considerable interest has been shown in application of these materials for low (400-650 degrees C) temperature operation of solid oxide fuel cells (SOFCs). In this paper, our experimental data about the influence of microstructure at the atomic level on electrochemical properties were reviewed in order to develop high quality doped CeO2 electrolytes in fuel cell applications. Using this data in the present paper, our original idea for a design of nanodomain structure in doped CeO2 electrolytes was suggested. The nanosized powders and dense sintered bodies of M doped CeO2 (M:Sm,Gd,La,Y,Yb, and Dy) compounds were fabricated. Also nanostiructural features in these specimens were introduced for conclusion of relationship between electrolytic properties and domain structure in doped CeO2. It is essential that the electrolytic properties in doped CeO2 solid electrolytes reflect in changes of microstructure even down to the atomic scale. Accordingly, a combined approach of nanostructure fabrication, electrical measurement and structure characterization was required to develop superior quality doped CeO2 electrolytes in the fuel cells.

Influence of particle morphology on nanostructural feature and conducting property in Sm-doped CeO2 sintered body

Doped ceria (CeO2,) compounds are fluorite type oxides, which show oxide ionic conductivity higher than yttria stabilized zirconia (YSZ), in oxidizing atmospheres. As a consequence of this, considerable interest has been shown in application of these materials for 'low (500-650 degreesC)' or 'intermediate (650-800 degreesC)' temperature operation, solid oxide fuel cells (SOFCs). In this study, the authors prepared two kinds of nanosize Sm-doped CeO2 particles with different morphologies: one type was round and the other was elongated. Processing these powders with different morphology produced dense materials with very different ionic conducting properties and different nanoscale microstructures. Since both particles are very fine and well dispersed, sintered bodies with high density (relative density >95% of theoretical) could be prepared using both types of powder particles. The electrical conductivity of sintered bodies prepared from these powders with different starting morphologies was very different. Materials prepared from particles having a round shape were much higher than those produced using powders with an elongated morphology. Measured activation energies of the corresponding sintered samples showed a similar trend; round particles (60 kJ/mol), elongated particles (74 kJ/mol). While X-ray diffraction (XRD) profiles of these sintered materials were identical, diffuse scatter was observed in the back.-round of selected area electron diffraction pattern recorded from both sintered bodies. This indicated an underlying structure that appeared to have been influenced by the processing technology. Detailed observation using high-resolution transmission electron microscopy (HR-TEM) revealed that the size of microdomain with ordering of cations in the sintered body made from round shape particles was much smaller than that of the sintered body made from elongated particles. Accordingly, it is concluded that the morphology of doped CeO2 powders strongly influenced the microdomain size and electrolytic properties in the doped CeO2 sintered body. (C) 2004 Elsevier B.V. All rights reserved.

Hydrogen from coal: Production and utilisation technologies

Error condition detected Although coal may be viewed as a dirty fuel due to its high greenhouse emissions when combusted, a strong case can be made for coal to be a major world source of clean H-2 energy. Apart from the fact that resources of coal will outlast oil and natural gas by centuries, there is a shift towards developing environmentally benign coal technologies, which can lead to high energy conversion efficiencies and low air pollution emissions as compared to conventional coal fired power generation plant. There are currently several world research and industrial development projects in the areas of Integrated Gasification Combined Cycles (IGCC) and Integrated Gasification Fuel Cell (IGFC) systems. In such systems, there is a need to integrate complex unit operations including gasifiers, gas separation and cleaning units, water gas shift reactors, turbines, heat exchangers, steam generators and fuel cells. IGFC systems tested in the USA, Europe and Japan employing gasifiers (Texaco, Lurgi and Eagle) and fuel cells have resulted in energy conversions at efficiency of 47.5% (HHV) which is much higher than the 30-35% efficiency of conventional coal fired power generation. Solid oxide fuel cells (SOFC) and molten carbonate fuel cells (MCFC) are the front runners in energy production from coal gases. These fuel cells can operate at high temperatures and are robust to gas poisoning impurities. IGCC and IGFC technologies are expensive and currently economically uncompetitive as compared to established and mature power generation technology. However, further efficiency and technology improvements coupled with world pressures on limitation of greenhouse gases and other gaseous pollutants could make IGCC/IGFC technically and economically viable for hydrogen production and utilisation in clean and environmentally benign energy systems. (c) 2005 Elsevier B.V. All rights reserved.

The role of carbon in fuel cells

Carbon possesses unique electrical and structural properties that make it an ideal material for use in fuel cell construction. In alkaline, phosphoric acid and proton-exchange membrane fuel cells (PEMFCs), carbon is used in fabricating the bipolar plate and the gas-diffusion layer. It can also act as a support for the active metal in the catalyst layer. Various forms of carbon - from graphite and carbon blacks to composite materials - have been chosen for fuel-cell components. The development of carbon nanotubes and the emergence of nanotechnology in recent years has therefore opened up new avenues of matenials development for the low-temperature fuel cells, particularly the hydrogen PEMFC and the direct methanol PEMFC. Carbon nanotubes and aerogels are also being investigated for use as catalyst support, and this could lead to the production of more stable, high activity catalysts, with low platinum loadings (< 0.1 Mg cm(-2)) and therefore low cost. Carbon can also be used as a fuel in high-temperature fuel cells based on solid oxide, alkaline or molten carbonate technology. In the direct carbon fuel cell (DCFC), the energy of combustion of carbon is converted to electrical power with a thermodynamic efficiency close to 100%. The DCFC could therefore help to extend the use of fossil fuels for power generation as society moves towards a more sustainable energy future. (c) 2006 Elsevier B.V. All rights reserved.

Analytical electron microscopy of proton exchange membrane fuel cells

Microtome sections of proton exchange membrane cells produce a wide range of information ranging from macroscopic distribution of components through specimens in which the detailed distribution of catalyst particles can be observed. Using modern data management practices it is possible to combine information at different scales and correlate processing and performance data. Analytical electron microscopy reveals the compositional variations across used cells at the electrolyte/electrode interface. In particular analytical techniques indicate that sulphur concentrations are likely to diminish at the interface Nafion/anode interface. © 2006 Elsevier B.V. All rights reserved.

Molten carbonate fuel cells

Over the past 12 months, developments in both porous and non-porous materials for the molten carbonate fuel cell (MCFC) should lead to significantly increased stack lifetimes. Lithium-sodium carbonate is emerging as the material of choice for the electrolyte and has been tested in a 10 kW scale stack. Several new cathode materials, with lower dissolution rates in the electrolyte than state-of-the-art NiO, have been tested. However a significant finding is that the dissolution rate of NiO can also be reduced by an order of magnitude by preparing it as a functional nanomaterial. Although most developers continue to use nickel anodes, recent tests with ceramic oxides anodes open up the prospects of reduced carbon deposition and future cells running directly on dry methane. (c) 2004 Published by Elsevier Ltd.

Microbial Fuel Cells: Methodology and Technology

Microbial fuel cell (MFC) research is a rapidly evolving field that lacks established terminology and methods for the analysis of system performance. This makes it difficult for researchers to compare devices on an equivalent basis. The construction and analysis of MFCs requires knowledge of different scientific and engineering fields, ranging from microbiology and electrochemistry to materials and environmental engineering. DescribingMFCsystems therefore involves an understanding of these different scientific and engineering principles. In this paper, we provide a review of the different materials and methods used to construct MFCs, techniques used to analyze system performance, and recommendations on what information to include in MFC studies and the most useful ways to present results.

Operation of polymer electrolyte membrane fuel cells with dry feeds: Design and operating strategies

The operation of polymer electrolyte membrane fuel cells (PEMFCs) with dry feeds has been examined with different fuel cell flow channel designs as functions of pressure, temperature and flow rate. Auto-humidified (or self-humidifying) PEMFC operation is improved at higher pressures and low gas velocities where axial dispersion enhances back-mixing of the product water with the dry feed. We demonstrate auto-humidified operation of the channel-less, self-draining fuel cell, based on a stirred tank reactor; data is presented showing auto-humidified operation from 25 to 115 degrees C at 1 and 3 atm. Design and operating requirements are derived for the auto-humidified operation of the channel-less, self-draining fuel cell. The auto-humidified self-draining fuel cell outperforms a fully humidified serpentine flow channel fuel cell at high current densities. The new design offers substantial benefits for simplicity of operation and control including: the ability to self-drain reducing flooding, the ability to uniformly disperse water removing current gradients and the ability to operate on dry feeds eliminating the need for humidifiers. Additionally, the design lends itself well to a modular design concept. (c) 2005 Elsevier B.V. All rights reserved.

Characterization of titanium phosphate as electrolytes in fuel cells

Titanium phosphate is currently a promising material for proton exchange membrane fuel cells applications (PEMFC) allowing for operation at high temperature conditions. In this work, titanium phosphate was synthesized from tetra iso-propoxide (TTIP) and orthophosphoric acid (H3PO4) in different ratios by a sol gel method. High BET surface areas of 271 m(2).g(-1) were obtained for equimolar Ti:P samples whilst reduced surface areas were observed by varying the molar ratio either way. Highest proton conductivity of 5.4 x 10(-2) S.cm(-1) was measured at 20 degrees C and 93% relative humidity (RH). However, no correlation was observed between surface area and proton conductivity. High proton conductivity was directly attributed to hydrogen bonding in P-OH groups and the water molecules retained in the sample structure. The proton conductivity increased with relative humidity, indicating that the Grotthuss mechanism governed proton transport. Further, sample Ti/P with 1:9 molar ratio showed proton conductivity in the order of 10(-1) S.cm(-1) (5% RH) and similar to 1.6x10(-2) S.cm(-1) (anhydrous condition) at 200 degrees C. These proton conductivities were mainly attributed to excess acid locked into the functionalized TiP structure, thus forming ionisable protons.

Hydrogen generation from liquid phase catalytic reforming of sugar solutions using metal-supported catalysts

Most of the hydrogen production processes are designed for large-scale industrial uses and are not suitable for a compact hydrogen device to be used in systems like solid polymer fuel cells. Integrating the reaction step, the gas purification and the heat supply can lead to small-scale hydrogen production systems. The aim of this research is to study the influence of several reaction parameters on hydrogen production using liquid phase reforming of sugar solution over Pt, Pd, and Ni supported on nanostructured supports. It was found that the desired catalytic pathway for H-2 production involves cleavage of C-C, C-H and O-H bonds that adsorb on the catalyst surface. Thus a good catalyst for production of H2 by liquid-phase reforming must facilitate C-C bond cleavage and promote removal of adsorbed CO species by the water-gas shift reaction, but the catalyst must not facilitate C-O bond cleavage and hydrogenation of CO or CO2. Apart from studying various catalysts, a commercial Pt/gamma-alumina catalyst was used to study the effect of temperature at three different temperatures of 458, 473 and 493 K. Some of the spent catalysts were characterised using TGA, SEM and XRD to study coke deposition. The amorphous and organised form of coke was found on the surface of the catalyst. (C) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.