Comparative study of electrophoretic deposition of doped BaCeO3-based films on La2NiO4+δ and La1.7Ba0.3NiO4+δ cathode substrates

This paper presents the results of a comparative study of methods to prevent the loss of barium during the formation of thin-film proton-conducting electrolyte BaCe0.89Gd0.1Cu0.01O3-δ (BCGCuO) on La2NiO4+δ-based (LNO) cathode substrates by electrophoretic deposition (EPD). Three different methods of the BCGCuO film coating were considered: the formation of the BCGCuO electrolyte film without (1) and with a protective BaCeO3 (BCO) film (2) on the LNO electrode substrate and the formation of the BCGCuO electrolyte film on a modified La1.7Ba0.3NiO4+δ (LBNO) cathode substrate (3). After the cyclic EPD in six stages, the resulting BCGCuO film (6 μm) (1) on the LNO substrate was completely dense, but the scanning electron microscope (SEM) analysis revealed the absence of barium in the film caused by its intensive diffusion into the substrate and evaporation during the sintering. The BCO layer prevented the barium loss in the BCGCuO film (2); however, the protective film possessed a porous island structure, which resulted in the deterioration of the film's conductivity. The use of the modified LBNO cathode also effectively prevented the loss of barium in the BCGCuO film (3). A BCGCuO film whose conductivity behavior most closely resembled that of the compacts was obtained by using this method which has strong potential for practical applications in solid oxide fuel cell (SOFC) technology. © 2019 by the authors.Government Council on Grants, Russian FederationFunding: This research was funded by the Government of the Russian Federation (Agreement 02.A03.21.0006, Act 211)

Ceria-based materials for high-temperature electrochemistry applications

This paper describes the experimental studies of multi-component solid state electrolytes based on CeO2 and their application in intermediate temperature electrochemical devices. Two important aspects are emphasized: the effect of different dopants’ ionic radius and concentration on the electrical properties of CeO2-based solid solutions in air and the influence of combined dopants on the electrolytic properties of solid electrolytes from the standpoint of the critical oxygen partial pressure pO2 at which point the values of the electronic and ionic components of conductivity are equal. Examples of usage of the developed multi-component Ce0.8(Sm0.75Sr0.2Ba0.05)0.2O2-δ electrolyte synthesized by solid state, laser evaporation and combustion methods and composites on the base of Ce0.8(Sm0.8Sr0.2)0.2O2−d electrolyte as a component of electrochemical devices such as solid oxide fuel cell, gas sensors and as a component of the mixed ionic and electronic conducting (MIEC) membranes for hydrogen and syngas gas production are cited.The present work was financially supported by Russian Foundation for Basic Research and Government of Sverdlovsk region, grant no. 13-03-96098

Opportunities, Challenges and Prospects for Electrodeposition of Thin-Film Functional Layers in Solid Oxide Fuel Cell Technology

Electrolytic deposition (ELD) and electrophoretic deposition (EPD) are relevant methods for creating functional layers of solid oxide fuel cells (SOFCs). This review discusses challenges, new findings and prospects for the implementation of these methods, with the main emphasis placed on the use of the ELD method. Topical issues concerning the formation of highly active SOFC electrodes using ELD, namely, the electrochemical introduction of metal cations into a porous electrode backbone, the formation of composite electrodes, and the electrochemical synthesis of perovskite-like electrode materials are considered. The review presents examples of the ELD formation of the composite electrodes based on porous platinum and silver, which retain high catalytic activity when used in the low-temperature range (400–650 °C). The features of the ELD/EPD co-deposition in the creation of nanostructured electrode layers comprising metal cations, ceramic nanoparticles, and carbon nanotubes, and the use of EPD to create oriented structures are also discussed. A separate subsection is devoted to the electrodeposition of CeO2-based film structures for barrier, protective and catalytic layers using cathodic and anodic ELD, as well as to the main research directions associated with the deposition of the SOFC electrolyte layers using the EPD method. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This research was funded by the Russian Foundation for Basic Research, grant number 20-03-00151

Overview of Approaches to Increase the Electrochemical Activity of Conventional Perovskite Air Electrodes

The progressive research trends in the development of low-cost, commercially competitive solid oxide fuel cells with reduced operating temperatures are closely linked to the search for new functional materials as well as technologies to improve the properties of established materials traditionally used in high-temperature devices. Significant efforts are being made to improve air electrodes, which significantly contribute to the degradation of cell performance due to low oxygen reduction reaction kinetics at reduced temperatures. The present review summarizes the basic information on the methods to improve the electrochemical performance of conventional air electrodes with perovskite structure, such as lanthanum strontium manganite (LSM) and lanthanum strontium cobaltite ferrite (LSCF), to make them suitable for application in second generation electrochemical cells operating at medium and low temperatures. In addition, the information presented in this review may serve as a background for further implementation of developed electrode modification technologies involving novel, recently investigated electrode materials. © 2023 by the authors.Russian Science Foundation, RSF: 23-23-00083The research funding from the Russian Science Foundation (agreement 23-23-00083) is gratefully acknowledged

Performance Enhancement of Ce0.8Sm0.2O1.9-Supported SOFC by Electrophoretic Formation of Modifying BaCe0.8Sm0.2O3 and Ce0.8Sm0.1Pr0.1O1.9 Layers

The strategy to increase the performance of the single solid oxide fuel cell (SOFC) with a supporting membrane of Ce0.8Sm0.2O1.9 (SDC) electrolyte has been implemented in this study by introducing a thin anode barrier layer of the BaCe0.8Sm0.2O3 + 1 wt% CuO (BCS-CuO) electrolyte and, additionally, a modifying layer of a Ce0.8Sm0.1Pr0.1O1.9 (PSDC) electrolyte. The method of electrophoretic deposition (EPD) is used to form thin electrolyte layers on a dense supporting membrane. The electrical conductivity of the SDC substrate surface is achieved by the synthesis of a conductive polypyrrole sublayer. The kinetic parameters of the EPD process from the PSDC suspension are studied. The volt-ampere characteristics and power output of the obtained SOFC cells with the PSDC modifying layer on the cathode side and the BCS-CuO blocking layer on the anode side (BCS-CuO/SDC/PSDC) and with a BCS-CuO blocking layer on the anode side (BCS-CuO/SDC) and oxide electrodes have been studied. The effect of increasing the power output of the cell with the BCS-CuO/SDC/PSDC electrolyte membrane due to a decrease in the ohmic and polarization resistances of the cell is demonstrated. The approaches developed in this work can be applied to the development of SOFCs with both supporting and thin-film MIEC electrolyte membranes. © 2023 by the authors.The study had no external financial support

Electrophoretic Deposition and Characterization of the Doped BaCeO3 Barrier Layers on a Supporting Ce0.8Sm0.2O1.9 Solid‐State Electrolyte

In this study, the technology of electrophoretic deposition (EPD) micrometer barrier layers based on a BaCe0.8Sm0.19Cu0.1O3 (BCSCuO) protonic conductor on dense carrying Ce0.8Sm0.2O1.9 (SDC) solid‐state electrolyte substrates is developed. Methods for creating conductive sublayers on non-conductive SDC substrates under EPD conditions, such as the synthesis of a conductive polypyrrole (PPy) layer and deposition of a layer of finely dispersed platinum from a suspension of its powder in isopropanol, are proposed. The kinetics of disaggregation, disperse composition, electrokinetic potential, and the effect of adding iodine to the BCSCuO suspension on these parameters as factors determining the preparation of stable suspensions and successful EPD processes are explored. But-ton cells based on a carrying SDC electrolyte of 550 μm in thickness with BCSCuO layers (8–35 μm) on the anode, cathode, and anode/cathode side, and Pt electrodes are electrochemically tested. It was found that the effect of blocking the electronic current in the SDC substrate under OCV conditions was maximal for the cells with barrier layers deposited on the anode side. The technology developed in this study can be used to fabricate solid oxide fuel cells with doped CeO2 electrolyte membranes characterized by mixed ionic–electronic conductivity (MIEC) under reducing atmospheres. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 22-23-00066This work was supported by the Russian Science Foundation (Project No. 22-23-00066, https://rscf.ru/en/project/22-23-00066 (accessed on 8 February 2022))

Electrophoretic Deposition and Characterization of Er-Doped Bi2O3 Cathode Barrier Coatings on Non-Conductive Ce0.8Sm0.2O1.9 Electrolyte Substrates

In this study, the formation of thin-film barrier coatings based on a highly conductive Bi1.60Er0.4O3 (EDB) solid electrolyte on supporting Ce0.8Sm0.2O1.9 (SDC) electrolyte substrates was implemented for the first time using electrophoretic deposition (EPD). The electrokinetic properties of EDB-based suspensions in a non-aqueous dispersion medium of isopropanol modified with small additions of polyethyleneimine (PEI, 0.26 g/L) and acetylacetone (0.15 g/L), as well as in a mixed isopropanol/acetylacetone (70/30 vol.%) medium, were studied. The dependences of the thickness of the EDB coatings on voltage and deposition time were obtained using deposition on a model Ni foil electrode. Preliminary synthesis of a conductive polypyrrole (PPy) polymer film was used to create surface conductivity on non-conductive SDC substrates. The efficiency of using a modified dispersion medium based on isopropanol to obtain a continuous EDB coating 12 μm thick, sintered at a temperature of 850 °C for 5 h, is shown. The microstructure and morphology of the surface of the EDB coating were studied. A Pt/SDC/EDB/Pt cell was used to characterize the coating’s conductivity. The EPD method is shown to be promising for the formation of barrier coatings based on doped bismuth oxide. The developed method can be used for creating cathode barrier layers in SOFC technology. © 2023 by the authors

Direct Electrophoretic Deposition and Characterization of Thin‐film Membranes Based on Doped BaCeO3 and CeO2 for Anode‐supported Solid Oxide Fuel Cells

In this work, a technology was developed for the formation of BaCe0.8Sm0.2O3+1 wt% CuO (BCS‐CuO)/Ce0.8Sm0.2O1.9 (SDC) thin‐film electrolyte membranes for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs) on porous NiO‐BCS‐CuO anode substrates using direct electrophoretic deposition (EPD). The effect of increasing the zeta potential when modifying the base suspension of a micro‐sized SDC‐gn powder (glycine–nitrate method) with the addition of a SDC‐lec nanopowder (laser evaporation–condensation) was investigated. Dependences of the current strength on the deposition time and the deposited weight on the EPD voltage were obtained, and evolution of the morphology of the coatings during the modification of the SDC‐gn suspension and a suspension of BCS‐CuO powder was studied. The compatibility of the shrinkage kinetics of the SDC, the BCS‐ CuO electrolyte coatings and the NiO‐BCS‐CuO anode substrate was studied during the high‐temperature sintering. Dense BCS‐CuO/SDC films of different thicknesses were obtained for the first time on porous NiO‐BCS‐CuO anode substrates and comprehensive microstructural and electrochemical studies were carried out. The developed technology can be applied to the formation of anode‐supported SOFCs with thin‐film electrolyte membranes. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Russian Foundation for Basic Research, РФФИ: 20-03-00151Funding: The work was financially supported by the Russian Foundation for Basic Research, grant № 20-03-00151

Place of Electrophoretic Deposition Among Thin-Film Methods Adapted to the Solid Oxide Fuel Cell Technology: a Short Review

Thin film technologies have attracted ever-growing interest in different industrial areas. Concerning solid oxide fuel cells (SOFCs), especially devices operating in the intermediate temperature range, such technologies are applied particularly for the deposition of dense, gas-tight electrolyte films with a thickness of several μm to decrease ohmic resistance and enhance the cell performance. The main requirements for the technology selected are its low cost, simplicity of the equipment used, short deposition time and flexibility regarding the cell shape. First, we overview thin-film technologies adapted to the deposition of SOFC functional layers, discussing their strengths and weaknesses, with special attention given to electrophoretic deposition (EPD) as being the most simple and cost-effective colloidal method to fabricate different electrolyte films. Then we present the contribution of our scientific group in the development of the EPD method. The preparation of stable suspensions for the EDP is one of the key requirements for its successful implementation and reproducibility; this was considered in detail and the effect of self-stabilization in suspensions based on nanopowders (7–15 nm), obtained by the method of laser evaporation with consequent condensation, was discussed. Such suspensions, exhibiting high positive ζ-potential values (30–50 mV), were shown to be suitable for EPD without the addition of dispersants or iodine. The requirements for the electrode substrates were formulated and a model of particle aggregation near the porous substrate surface was proposed. Deposition parameters were established for different electrolyte films – commonly used yttria-stabilized zirconia, single and multiply doped CeO2 and proton-conducting doped BaCeO3 electrolytes. As was shown, the deposition on the highly conducting cathode substrates is simpler to implement than the EPD on non-conducting anode substrates and, in addition, it produces high quality films which render high OCV values and superior SOFC performance.This work was performed within the framework of a budget task of the Institute of Electrophysics, UB RAS and the SOFC development task of the Institute of High Temperature Electrochemistry, UB RAS, and partially supported by the Government of the Russian Federation (Agreement 02.A03.21.0006, Act 211)

Challenges of Formation of Thin-film Solid Electrolyte Layers on Non-Conductive Substrates by Electrophoretic Deposition

In this work, the challenges associated with the formation of single and bilayer coatings based on Ce0.8 Sm0.2 O1.9 (SDC) and CuO modified BaCe0.5 Zr0.3 Y0.1 Yb0.1 O3−δ (BCZYYbO-CuO) solid state electrolytes on porous non-conducting NiO-SDC anode substrates by the method of electrophoretic deposition (EPD) are considered. Various approaches that had been selected after analysis of the literature data in order to carry out the EPD, are tested: direct deposition on a porous non-conductive anode substrate and multiple options for creating the conductivity of the anode substrate under EPD conditions such as the reduction of the NiO-SDC substrate and the creation of a surface conducting sublayer via synthesizing a polypyrrole (PPy) film. New effective method was proposed based on the deposition of a platinum layer on the front side of the substrate. It was ascertained that, during the direct EPD on the porous NiO-SDC substrate, the formation of a continuous coating did not occur, which may be due to insufficient porosity of the substrate used. It was shown that the use of reduced substrates leads to cracking and, in some cases, to the destruction of the entire SDC/NiO-SDC structure. The dependence of the electrolyte film sinterability on the substrate shrinkage was studied. In contrast to the literature data, the use of the substrates with a reduced pre-sintering temperature had no pronounced effect on the densification of the SDC electrolyte film. It was revealed that complete sintering of the SDC electrolyte layer with the formation of a developed grain structure is possible at a temperature of 1550◦ C. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: The work was financially supported by the Russian Foundation for Basic Research, grant № 20-03-00151. Investigation of the kinetic properties of the suspensions was performed within the framework of the state assignment of IEP UB RAS (EPD thin-layer coatings, No. AAAA-A19-119061090040-7). The study was in part carried out on the equipment of the Shared Access Center of “Composition of compounds” IHTE UB RAS and the Shared Access Centers of the IEP UB RAS and ISSC UB RAS