Solid Electrolytes: Applications in Heterogeneous Catalysis and Chemical Cogeneration

Abstract

Solid electrolytes have found applications in several areas, including (a) sensors, (b) separators, (c) solid oxide fuel cells, and (d) solid-state batteries. In addition, solid electrolytes have been used in the construction of solid electrolyte cell reactors (SECRs), in which heterogeneous catalytic reactions have been studied. Also, SECRs have been used as chemical cogenerative fuel cells, i.e., for the simultaneous production of electricity and useful compounds. In the present work, a survey of the studies conducted in SECRs is presented. The fundamental operating principles, results in technologically important reactions, and the hurdles that should be overcome to bring SECRs into industrial practice are discussed.

Electrochemical Synthesis of Ammonia in Solid Electrolyte Cells

“…This double layer alters the work function of the catalyst surface resulting in a reversible alteration of the catalytic reaction rate (Vayenas et al, 2001;Vayenas and Koutsodontis, 2008;Vayenas, 2011). NEMCA is a powerful tool in heterogeneous catalysis because (a) the surface modification can be monitored electrochemically and in a reversible manner and (b) the increase in the reaction rate can exceed the rate of ion supply by several orders of magnitude (Garagounis et al, 2011;Vayenas, 2011).…”

“…Thus, the electrolyte properties, and in particular the protonic conductivity, are crucial because they determine the maximum rate of proton supply. The conductivity of a solid electrolyte increases exponentially with temperature and is inversely proportional to the thickness of the electrolyte (Gellings and Bouwmeester, 1997). By reducing the electrolyte thickness, the same proton flux is attainable at a lower temperature.…”

“…The continuous search for more active catalysts resulted in operation at lower temperatures and consequently, at lower pressures. Parallel to catalyst optimization, research efforts also focus on the investigation of new methods for ammonia synthesis, including the electrochemical synthesis in aqueous or solid electrolyte cells (Garagounis et al, 2011). Several studies in which ammonia was electrochemically produced in aqueous media have been reported (Kordali et al, 2000;Kőleli and Rőpke, 2006).…”

Production of H2 and C2 hydrocarbons from methane in a proton conducting solid electrolyte cell using a Au–5Ce–5Na2WO4/SiO2 anode

“…It can be seen that in the absence of O 2 at the anode, L is close to unity, while for low P O2 values, L's as high as 10, were observed. So far, very few reports can be found in the literature, in which H þ or mixed-conducting SEMRs were used to study the present reaction system [3,9]. These works mainly focused on the production of C 2 hydrocarbons and not on the simultaneous production and separation of hydrogen.…”

Direct production of flexible H2/CO synthesis gas in a solid electrolyte membrane reactor

“…In addition, for the case of ethanol partial oxidation reaction, pure O 2 free of N 2 can be in situ supplied through an integrate steam electrolysis process which allows the further production of H 2 avoiding an energetic intensive air separation unit. These kinds of reactor configurations have already been used in other catalytic reactions such as oxidative coupling of methane, oxidation and reduction of NO x , ammonia synthesis reactions as described in detail in previous reviews [10,[16][17][18][19].…”