1. Introduction 46372. Theoretical Methodologies and Simulation Tools 46402.1. Ab Initio Quantum Chemistry 46412.2. Molecular Dynamics 46422.2.1. Classical Molecular Dynamics and MonteCarlo Simulations46432.2.2. Empirical Valence Bond Models 46442.2.3. Ab Initio Molecular Dynamics (AIMD) 46452.3. Poisson−Boltzmann Theory 46452.4. Nonequilibrium Statistical Mechanical IonTransport Modeling46462.5. Dielectric Saturation 46473. Transport Mechanisms 46483.1. Proton Conduction Mechanisms 46483.1.1. Homogeneous Media 46483.1.2. Heterogeneous Systems (ConfinementEffects)46553.2. Mechanisms of Parasitic Transport 46613.2.1. Solvated Acidic Polymers 46613.2.2. Oxides 46654. Phenomenology of Transport inProton-Conducting Materials for Fuel-CellApplications46664.1. Hydrated Acidic Polymers 46664.2. PBI−H

/pdf/transport-in-proton-conductors-for-fuel-cell-applications-3gvrtpo4jv.pdf

Transport in proton conductors for fuel-cell applications: simulations, elementary reactions, and phenomenology.

Solid oxide fuel cells (SOFCs) have the promise to improve energy efficiency and to provide society with a clean energy producing technology. The high temperature of operation (500−1000 °C) enables the solid oxide fuel cell to operate with existing fossil fuels and to be efficiently coupled with turbines to give very high efficiency conversion of fuels to electricity. Solid oxide fuel cells are complex electrochemical devices that contain three basic components, a porous anode, an electrolyte membrane, and a porous cathode. In this short review, a survey of the types and properties of materials that have been considered for each of these components is presented with an emphasis on the requirements for operation at intermediate temperature (500−800 °C). Some directions for future research are discussed.

Materials for Solid Oxide Fuel Cells

Bismuth oxide systems exhibit high oxide ion conductivity and have been proposed as good electrolyte materials for applications such as solid oxide fuel cells and oxygen sensors. However, due to their instability under conditions of low oxygen partial pressures there has been difficulty in developing these materials as alternative electrolyte materials compared to the state-of-the-art cubic stabilised zirconia electrolyte. Bismuth oxide and doped bismuth oxide systems exhibit a complex array of structures and properties depending upon the dopant concentration, temperature and atmosphere. In this paper we comprehensively review the structures, thermal expansion, phase transitions, electrical conductivity and stability of bismuth oxide and doped bismuth oxide systems. ©

Bismuth based oxide electrolytes— structure and ionic conductivity

The performance of the oxide-ion electrolyte of a solid oxide fuel cell (SOFC) is critical to the development of an intermediate-temperature system. Although yttria-stabilized zirconia is the electrolyte used in SOFCs under commercial development, other candidate materials are now available, and there remains a strong motivation to search for new, improved oxide-ion electrolytes. The leading contenders are discussed not only with respect to their oxide-ion conductivity, but also with respect to mechanical and chemical compatibility with the electrodes and the working environment at each electrode.

Oxide-ion electrolytes

Oxide ion conducting solid electrolytes based on Bi2O3

Thermodynamic and kinetic considerations for Bi2O3-based electrolytes

Galvanic cells with solid electrolytes were used to determine activity‐composition diagrams in the systems. Activities of were determined from the measured electromotive force (EMF) values while those of were estimated by Gibbs‐Duhem integration. Equilibrium phases were identified by x‐ray diffraction. In the stability range of the rhombohedral phase , the activity of exhibited a drastic decrease with increasing amount of in all three systems. system showed the widest rhombohedral phase field and the lowest activity of (0.117) in the composition, , at 630°C. Partial molar entropies of dissolution of were determined from the temperature dependence of EMF. On the side, partial molar entropies of dissolution of were compared with a theoretical calculation of the configuration part of the partial molar entropy. A free energy vs.composition diagram was constructed for the system.

Thermodynamic Investigations of Bi2 O 3 ‐ MO ( M = Ca , Sr , and Ba ) Systems Using Galvanic Cells

Many oxygen-deficient oxide perovskites are oxygen ion conductors in a dry environment. However, in a humid atmosphere, they absorb water to fill up oxygen vacancies, release quasi-free protons into the structure, and thereby become proton conductors. Absorption of water requires the transport of both protons and oxygen ions. This effectively leads to the transport of H 2 O under its chemical potential gradient. The present manuscript develops relationships between the chemical diffusion coefficient of H 2 O and the diffusion coefficients of protons and oxygen vacancies with an emphasis on the role of solution thermodynamics.

Hyun Deok Baek

Papers

Thermodynamic and kinetic considerations for Bi2O3-based electrolytes

Thermodynamic Investigations of Bi2 O 3 ‐ MO ( M = Ca , Sr , and Ba ) Systems Using Galvanic Cells

Chemical Diffusion Coefficient of H2O in AB(1−x)B′xO(3−x/2)‐Type Perovskites

Reply to “Comment on ‘Chemical Diffusion Coefficient of H2O in AB(1−x)B′xO(3−x/2)‐Type Perovskites’”