Augustin J. Mcevoy

• Bsc MSc BD DPhil
• Retired at Swiss Federal Institute of Technology in Lausanne

In reply to Abbas Ali Saberi's article "Penalizing Iranian research" (Forum, April p17).

A diversified energy technology is an imperative for our future welfare, and solar photovoltaic systems are rapidly finding a place as a renewable generating system for electricity. Conventional solar photovoltaic cells are solid state, usually silicon, devices and their production involves considerable investment in capital and in energy. Given th...

The Voltaic pile, invented here on Lake Como 200 years ago, was a crucial step in the development of electrical engineering. For the first time a controlled and reliable source of electric current was available. The science of electrochemistry developed rapidly and is now a key contributor, not just to energy technology but also, for example, to me...

Some preliminary results have shown that concentrated light irradiation over Ru(3.8%)/TiO2 significantly affects the methanation reaction (more than 50% of the global rate of reaction). The use of a cut-off filter at 455 nm and of a support that is not photoactive (zeolite SK40) has established a similar photoeffect on the reaction rate. So, even i...

Enormous leaps forward in the efficiency and the economy of solar cells are being made at a furious pace. New materials and manufacturing processes have opened up new realms of possibility for the application of solar cells. Crystalline silicon cells are increasingly making way for thin film cells, which are spawning experimentation with third-gene...

In his reply to Brian Drummond's letter on "Proper perspective and nuclear power" (August p19), I am surprised that Paul Grant allowed Drummond's reference to the Nestorenko et al. publication (2009 Annals New York Acad. Sciences 1181) to pass unchallenged. This document, with its claim that the Chernobyl accident has already killed several hundred...

In his review of Tyler Hamilton's book Mad Like Tesla (May pp44–45), Roger Bridgman writes that "in energy supply, obviously, companies cannot simply junk huge infrastructure investments in favour of something new, however good it might be". But that is exactly what Angela Merkel's administration has done in Germany with its anti-nuclear policy.

As part of the growing sustainable and renewable energy movement, the design, manufacture and use of photovoltaic devices is increasing in pace and frequency. The Handbook of Photovoltaics will be a 'benchmark' publication for those involved in the design, manufacture and use of these devices. The Handbook covers the principles of solar cell functi...

Physics World's reporting of the nuclear-policy consequences of the catastrophic Japanese earthquake and tsunami has so far been limited to a paragraph in the Sidebands column (July p9) under the headline "Europe scraps nuclear plans".

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

In this section, we will be concerned with applications of photoelectrochemical cells (PEC). The term “photoelectrochemical” refers to any situation wherein light is used to augment an electrochemical process; the prefix photo implies in particular radiation of some kind, typically visible light of a continuous frequency range (e.g., solar) or of a...

Fuel cells can be regarded as catalysed chemical reactors. They can therefore be highly sensitive to the purity of the relevant reagent, the fuel. The anode catalyst in the standard SOFC is a metal-ceramic composite characterised by rapid and significant deterioration of its activity when exposed to sulfur contaminants in the fuel, even in ppm. con...

Incident solar radiation is the most fundamental of the sustainable energy sources, being at the origin of all others - wind and wave, biomass and even fossil fuels which represent stored solar energy over a geological time scale. Only nuclear and geothermal sources are non-solar. The direct conversion of incident solar radiation into the most conv...

The sections in this article are

In any type of fuel cell, impurities in the fuel may be incompatible with either the anode material or the reforming catalyst, with potentially serious consequences. As a result a fuel-processing step is normally required before use of a commercial fuel. In the SOFC case sulfur is the element most likely to degrade a nickel cermet anode. In the pre...

Whereas the conventional solid oxide fuel cell uses an oxygen-ion conducting electroceramic, materials also exist which, at least over a restricted temperature range, perform as hydrogen ion, or proton, conductors. In principle, solid oxide fuel cells based on these materials are possible. With increasing temperature some degree of oxygen ion mobil...

The surface chemical behavior of the materials chosen for SOFC anodes determines the specification of a compatible fuel for reliable long-term operation. With the conventional nickel-zirconia cermet, for example, a hydrogen-carbon monoxide mixture can be used. Hydrocarbons on the other hand require a pre-reforming to avoid anode damage due to carbo...

Test and measurement methods, particularly electrochemical methods, applicable to fuel cell technology are reviewed. The difficulties of application of diagnostic tools and interpretation of results are highlighted. Specific requirements of the different fuel cell types, both high and low temperature variants, are dealt with. Finally, recently deve...

The electrochemical synthesis of conducting nanocones of Pt incorporated poly(3-methyl) thiophene, employing alumina membrane templates and its use as an electrode material for methanol oxidation is reported. The activity (131 mA/cm2 at +0.4 V versus Ag/AgCl for a Pt loading of 80 μg/cm2) of nanocone-based electrode was found to be more than one or...

Fuel cells will undoubtedly find widespread use in this new millennium in the conversion of chemical to electrical energy, as they offer very high efficiencies and have unique scalability in electricity-generation applications. The solid-oxide fuel cell (SOFC) is one of the most exciting of these energy technologies; it is an all-ceramic device tha...

At present dye-sensitised photosystems provide the only technically and economically credible alternative to the conventional and established solid state photovoltaic devices. Optical absorption by an electroactive dye and charge separation on the semiconductor take place on distinct sites within these photovoltaic cells, and in contrast to the sol...

This chapter provides an overview of the photoelectrochemical solar cells. In a photoelectrochemical cell a photoactive electrode is effectively integrated into an electrolytic cell. In a photoelectrochemical cell, injected electrons provide a current in an external circuit, returning to the redox electrolyte through a cathode in contact with it. T...

The role of an anode in a solid oxide fuel cell (SOFC) is to provide the sites for the fuel gas to react with the oxide ions delivered by the electrolyte, within a structure that also facilitates the necessary charge neutralization by its electronic conductivity. These functional considerations, together with the operating environment of the anode,...

Operation of solid oxide fuel cells with standard Ni-YSZ cermet anodes requires a partial reforming of any hydrocarbon fuel to avoid deactivation of the electrode. Direct oxidation of the fuel would simplify the system, but requires significant innovation in anode materials. Innovationen für Anoden – Katalyse und Direktoxidation Die Anwendung von F...

The physico-chemical origins of the performance loss in polymer electrolyte fuel cells operated at high current densities are investigated. This effect could be attributed to a shortage of water in the proton conducting membrane leading to an increase of the membrane proton-conduction resistance as well as to a increase of the activation overpotent...

In a Swiss consortium, the fabrication of anode-supported SOF cells by using simple and cheap fabrication techniques has been developed. The concept was demonstrated in a three-cell stack operated successfully at Sulzer Hexis by using reformed natural gas at around 800°C.

The present concepts evolved in the context of research and development of artificial photosynthetic systems. Our biosphere depends totally on the action of a porphyrin dye, chlorophyll, for its continued existance, since all food resources find their origin in photosynthesis. Equally, for much of our energy resources we rely on the same process, p...

Solid state ionic devices such as fuel cells and oxygen separation membranes require the adsorption of oxygen molecules, their dissociation into oxygen atoms, oxidation by charge exchange and entry of the resultant ion into the solid phase. The cathodes capable of sustaining these processes must themselves be stable in the high temperature environm...

As the current density on a solid oxide fuel cell element increases, the voltage is reduced from that, close to the Nernst potential, obtained under open-circuit conditions due to loss mechanisms, the ohmic resistance of the materials and polarisation effects at the interfaces, as well as any effect of fuel depletion. The ohmic losses are determine...

Oxygen diffusion is treated in a dense electronically conducting perovskite pellet blocked ionically on one surface, electronically on the other, and sealed on the cylindrical surface. Oxygen exchange at the electronically blocked surface is assigned first order reaction kinetics. An equivalent circuit model is suggested for the cell impedance by t...

In the apparent impasse concerning the identification of more promising new materials for intermediate temperature solid oxide fuel cells, and the imperative for the credibility of the technology that applications be proven in the short term, all relevant information from earlier work should be exploited to secure the stable and efficient operation...

In the apparent impasse concerning the identification of more promising new materials for intermediate temperature solid oxide fuel cells, and the imperative for the credibility of the technology that applications be proven in the short term, all relevant information from earlier work should be exploited to secure the stable and efficient operation...

Oxygen diffusion is treated in a dense electronically conducting cobaltate pellet blocked ionically on one surface, electronically on the other, and sealed on its cylindrical periphery. A procedure is developed for extracting the chemical diffusion and surface exchange coefficients for oxygen by use of the asymptotic equations derived for the curre...

Oxygen diffusion is treated in a dense electronically conducting perovskite pellet blocked ionically on one surface, electronically on the other, and sealed on the periphery. Oxygen exchange at the electronically blocked surface is assigned first order reaction kinetics. An equivalent circuit model is suggested for the cell impedance by the Laplace...

Solid electrolytes of cubic structure employed in Solid Oxide Fuel Cells (SOFC) like ceria (CeO2) and zirconia (ZrO2) are typically doped with a single selected element from the (Y, lanthanide)-series. Co-doping of ceria with several elements is investigated here in terms of its influence on ionic conductivity. It is found that, for a same total do...

La0·7Ca0·32CrO3, La0·75Ca0·15Sr0·1Cr0·95Mg0·05O3, La0·85Ca0·15CrO3 and La0·85Ca0·15Cr0·9Mg0·1O3 compounds were studied in reducing atmospheres containing hydrogen, methane and CO/CO2. They were found to exhibit liquid phase sintering except for La0·85Ca0·15CrO3. Mg enhanced the densification of stoichiometric LaCrO3. Current was found to affect the...

Porous composite cathodes for ceramic fuel cells containing (La0·8 Sr0·2)0·98MnO3 (LSM) and yttria stabilised zirconia (YSZ) were prepared by vacuum plasma spraying (VPS) on prefabricated planar cermet supported zirconia substrates. Three different types of LSM–YSZ-mixtures with volume-ratio of 50/50 or 70/30% and thickness of 20–50 microns have be...

Bulk diffusion and surface exchange coefficients of oxygen transport in SrCo0.5Fe0.5O3-δ and SrFeCo0.5Ox are determined by use of a solid state electrochemical technique, based on the analysis of cell current response to an applied potential step. While the formation of interfacial phases by reaction between the sample and the electrolyte may affec...

A thin metallic film electrode deposited on a porous substrate, in this case a glass frit, in which electrolyte is entrained, may permit electrochemical effects with gas-phase reagents. Direct current sputtering is a convenient physical deposition method to prepare these electrode[1–3]and catalyst[4]materials. By using appropriate sputtering parame...

Photosensitization of wide-band-gap semiconductors is a promising low-cost photovoltaic technology. We present herein recent advances in photovoltaic devices and related technologies which have been achieved at the Laboratory for Photonics and Interfaces of the EPFL. New photosensitizing molecules have been developed which exhibit an increased spec...

The impedance responses and current-overpotential characteristics were studied for oxygen reducing cathodes, stoichiometric La1 − xSrxMnO3 (x = 0.16 − 0.20) in solid oxide fuel cells, under varying conditions of temperature (700–900 °C) and oxygen partial pressure (1 − 10−4atm) for two distinctly different electrode morphologies (porous and dense s...

With the solid oxide-fuel cell, a technology exploiting ionic conductivity in electroceramic materials, small-scale co-generation plants for combined production of heat and electricity can achieve clean high-efficiency operation. However, with thermal activation of the cell chemistry, extremely high operating temperatures, about 1000°, are required...

The impedance responses and current-overpotential characteristics were studied for oxygen reducing cathodes, stoichiometric La1 − xSrxMnO3 (x = 0.16 − 0.20) in solid oxide fuel cells, under varying conditions of temperature (700–900 °C) and oxygen partial pressure (1 − 10−4atm) for two distinctly different electrode morphologies (porous and dense s...

A significant improvement in power output is achieved by percolation of catalyst elements into the YSZ electrolyte surface during fabrication of a solid oxide fuel cell (SOFC). The resulting surface is referred to hereafter as a domain. The catalysts allow the electrochemical reactions to take place in the domain. Together with current collecting e...

Standard solar cells exploit the physics of semiconductors in which the energy of absorbed photons excites charge-carrier pairs which are subsequently separated by the influence of a solid state junction to provide a photovoltage. In the nanocrystalline electrochemical cell, the optical absorber is a dye monolayer which after photo-excitation injec...

The insertion of a transition metal enriched domain between the cathode and yttria-stabilized zirconia (YSZ) electrolyte improves the obtainable current density and power output of a solid oxide fuel cell (SOFC). By electrochemical impedance spectroscopy, it is demonstrated that an optimized interface develops during the first cell operation under...

Various cathode materials for use in solid oxide fuel cells, yttria-stabilized zirconia based, were examined by ac impedance and their current-voltage characteristics recorded: platinum, gold, silver, and La0.8Sr0.2MnO3. The oxygen reduction reaction mechanisms for the different cases are presented, as well as conclusions for the optimal electrode...

This study demonstrates the use of electroless deposition for depositing anode and cathode electrocatalysts in solid-oxide fuel cells (SOFC). Ni, Pd, and Ag films produced by electroless deposition techniques were in intimate contact with the electrolyte yttria-stabilized zirconia, and were found to catalyze SOFC anodic and cathodic reactions. Powe...

Samples of yttria-stabilized zirconia manufactured by the following fabrication procedures, were obtained from commercial sources: (i) hot isostatic pressing; (ii) tape casting; (iii) vacuum plasma spraying, and (iv) calendering. The ionic conductivities of these samples were measured by (a) impedance spectroscopy; (b) the four-point probe method;...

The oxygen reduction mechanism at the interface O2,Ag/YSZ (yttria-stabilized zirconia) was investigated by impedance spectroscopy and current-overpotential recording. Oxygen partial pressure was varied between 10−4 and 1 atm, and temperature between 600 and 850°C. Both dense and porous silver electrodes were studied. Bulk diffusion of oxygen atoms...

Chemical oxidation of aniline at the liquid/liquid interface of two immiscible solvents results in the growth of an electroactive polymer membrane that exhibits redox behaviour similar to conventional electrodeposited polyaniline.

Because the charging of polyaniline films occurs in the bulk of the material rather than exclusively at the polymer-electrolyte interface, the use of thick polymer films for battery applications is justifiable. Here, we present a method for producing soluble polyaniline which can be cast to form free-standing films. Investigation by scanning electr...

It has long been accepted that world demand for energy will increase steadily for the foreseeable future, but more intensive exploitation of conventional sources seemed to provide an adequate supply. Now, however, the situation has entirely changed. Nonrenewable fuels need to be conserved and are ecologically unpopular; nuclear power presents socia...

The electrochemical behavior of polyaniline and structurally modified polyaniline has been studied in various nonaqueous media including solvents such as acetonitrile and propylene carbonate, together with LiClO4 or other salts. Employing special chronopotentiometric techniques on various polyaniline samples, anticipated battery performance has bee...

The impedance response of the cell O2,Pt/(Y2O3)0.06 (ZrO2)0.94/Pt,O2 is measured at temperatures between 600 and 850°C and oxygen partial pressures between 10−3 and 1 atm as well as in low vacuum. The experimental data agree very well with those encountered in Reference [1], where surface diffusion of adsorbed oxygen atoms on the platinum electrode...

The rate of electropolymerization of aniline can be significantly accelerated by the addition of small amounts of bifunctional species, polyelectrolytes or surfactants to the monomer solution. In the first case, using para-phenylene diamine (PPDA) for example, the morphology of the polyaniline (PANI) film is densely branched and fibrous. In the lat...

Fractal geometry tools are used in order to analyze several related problems in surface science, catalysis, and electrocatalysis. The effects of complex morphologies of adsorbents, catalysts, and electrodes on various molecular processes with these materials are determined both theoretically and experimentally. It is shown that fractal geometry pro...

The preparation of TiO2 photoanodes for dye-sensitized electrochemical devices was investigated. TiO2 precursors with different rates of hydrolysis were used to modify the microstructures of the resulting TiO2 photoanodes. The photoelectrochemical quantum yield for electrodes prepared from citrate remained low. Acetate precursors gave rise to elect...

Light is treated as heat in traditional thermodynamics. Photons are assigned a temperature but zero chemical potential. In processes such as photovoltaic or photochemical absorption, electroluminescence and chemiluminescence, the number of photons is related to that of other energy quanta, e.g. electron—hole pairs or chemical excitations. This lead...

The electropolymerisation of aniline is accelerated by the presence of sodium polyvinyl sulphonate in the monomer solution and can be initiated at a less anodic potential than in its absence while the densely compact structure of the polymer is retained.

Deviations from classical Cottrell behaviour have been observed for the time dependence of the current transient following a potential step at the interface between a rough textured semiconductor surface and a solution of an electroactive species, when that potential step causes the interface to pass from a blocking to a charge transfer state