Fundamental problems of hydrogen and renewable energy and fuel all technologies

Synthesis of complex oxide and metal-oxide hydrogen permeable systems for applications as components of solid oxide fuel cells

Schematic representation of the working principle of a solid oxide fuel cell with proton conductivity.

Area of applications

The developed ceramic and cermet materials with proton conductivity can be used for production of anode and electrolyte of solid oxide fuel cell (SOFC), potentiometric sensors for monitoring hydrogen partial pressure and detecting hydrogen in molten metals, membrane reactors for hydrogenation and dehydrogenation processes, and purification systems for the separation of hydrogen from other gases, in particular, for the purification and recovery of hydrogen isotopes by hydrogen pumps of fusion reactor. Moreover, the advantage of the proton-conducting ceramics is the low cost, high thermal and chemical stability, in contrast to hydrogen permeable metals such as palladium or microporous membranes.

Brief description

Proton conducting SOFC is an electrochemical device that converts chemical energy from the reaction of hydrogen with oxygen directly into electrical energy at temperatures of 400-800°C. A SOFC consists of a dence ceramic electrolyte, porous metal-ceramic anode and ceramic cathode. Barium zirconate (BaZrO₃) or cerate (BaCeO₃) based materials are usually used as electrolyte and anode’s ceramic component and have an orthorhombic crystal structure of perovskite (ABO₃). To improve the sinterability of these refractory compounds, 1-5 mol% of oxides of In, Zn, Sn, Bi, Ni, or Cu is added to a powder mixture. While Zr, Nb, Ti, Ta, Y oxides provide the chemical stability of BaCeO₃-based perovskites in CO₂ and H2O atmospheres. The conductivity of BaZrO₃ and BaCeO₃ perovskites is not sufficiently high and partial substitution of Zr or Ce atoms with other elements, such as rare earth, to increase the number of oxygen vacancies is required. Among the known synthesis methods of perovskites, the solid state reaction method is the most widely used where the initial metal oxides are mixed with BaCO₃ with subsequent solid state synthesis at 800-1200°C. The main advantages of this method are its simplicity, low cost of starting materials and high performance. This method is also commonly used for the synthesis of cermets for SOFCs. The metallic phase of the cermet is Ni (up to 50 vol.%), which is obtained by reducing NiO in the ceramic scaffold. Nickel serves as an electron conductor and catalyst while being insoluble in the ceramic component of the SOFC anode.

Expected properties

It is expected that the sinterability of the powders will be improved due to the optimization of the synthesis and sintering parameters, as a result anodes and electrolytes with the required structural parameters will be obtained at low sintering temperatures. The obtained new materials with improved properties will increase the lifetime and performance of the fuel cells with proton conductivity. The developed materials with enhanced performance can also be used in other applications where the permeability of the hydrogen proton is required.

Advantages

The developed technology for fabrication of hydrogen permeable materials will provide the obtaining of complex oxide and metal-oxide materials with comparable properties to those of common materials.

Competitors

The leading institutions in the development of materials for solid oxide fuel cells with proton conductivity are
National Institute for Materials Science (Japan),
University of Science and Technology of China (PRC),
University of Science and Technology (Saudi Arabia), University of Oslo (Norway),
University of Calgary (Canada),
University of Pavia (Italy).

State of project development

According to the literature search, the promising oxide and metal-oxide hydrogen permeable systems were proposed. The factors that affect the proton conductivity of the materials and their performance as SOFC elements are discussed. The pros and cons of the synthesis methods are considered. The influence of phase and structure parameters of materials on performance of SOFCs is reviewed. The main obstacles in obtaining the materials with the desired properties and the ways to overcome them are identified.

Contact information

Executing :Frantsevich Institute for Problems of Materials Science of NAS of Ukraine

Project 21 «Synthesis of complex oxide and metal-oxide hydrogen permeable systems for applications as components of solid oxide fuel cells».

Project leader:

Morozov Igor A.

chief Executive
(+38 044) 424-01-01

Е-mail:imorozov@i.ua

Bezdorozhev Oleksii V.

head of laboratory
(+38 044) 424-01-01

Е-mail:oleksii.bezdorozhev@gmail.com

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