Perovskite oxide-based nanohybrid for low-temperature thin-film solid oxide fuel cells fabricated <i>via</i> a facile and scalable electrochemical process

Park, Beom-Kyeong,Seo, Han Gil,Jung, WooChul,Lee, Jong-Won Elsevier 2018 Ceramics international Vol.44 No.15

<P><B>Abstract</B></P> <P>High-performance electrodes for energy conversion systems can be achieved through the selection of materials with appropriate functionality as well as fabricating the desired nanoarchitectures. Nanohybrids of metal and perovskite metal oxide have a great potential as electrodes owing to the combined advantages of the active constituents; however, the controlled hybridization in nanoscale is hindered by the conflicting nature of the metal and perovskite oxide, and it should involve cost-, energy- and time-intensive fabrication techniques. Here, we report an electrochemical process as a facile, cost-effective, and scalable route to fabricating metal–perovskite metal oxide nanohybrids with tailored architectures. We successfully fabricate a Pt@LaCoO<SUB>3</SUB> nanohybrid that consists of a conformal LaCoO<SUB>3</SUB> nanonetwork on a nanoporous Pt thin-film framework. We examine this nanohybrid as an electrode for thin-film-based, low-temperature solid oxide fuel cells and demonstrate that the synergistic nanostructuring of Pt@LaCoO<SUB>3</SUB> leads to exceptionally high oxygen reduction activity at reduced operating temperature and high stability.</P>

Catalytic activity of perovskite-type doped La_0.08Sr_0.92Ti_1-xM_xO_3-δ (M = Mn, Fe, and Co) oxides for methane oxidation

Yoon, J.S.,Lim, Y.S.,Choi, B.H.,Hwang, H.J. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.15

Transition metal doped La<SUB>0.08</SUB>Sr<SUB>0.92</SUB>M<SUB>0.20</SUB>Ti<SUB>0.80</SUB>O<SUB>3-δ</SUB> (M = Mn, Fe, and Co) perovskite oxides were synthesized by the Pechini method. The methane oxidation behavior and the polarization resistance of the solid oxide fuel cells (SOFCs) with the perovskite oxides as anode was subsequently measured as a function of operation temperature. Surface atomic concentrations of the perovskite oxides were evaluated using X-ray photoelectron spectroscopy (XPS) and their relationship to the catalytic activity were discussed with respect to the transition metal dopant. The complete oxidation of methane was predominant in the low-temperature region, while the partial oxidation of methane occurred at high temperatures. Fe- and Co-doped perovskites showed better catalytic activity for the methane oxidation reaction than Mn-doped powder. This phenomenon could be explained by the high atomic concentration with low oxidation states and the resulting high oxygen vacancy concentration in the Fe- and Co-doped perovskite powder samples.

An experimental and kinetic study of toluene oxidation over LaMn1−xBxO3 and La0.8A0.2Mn0.3B0.7O3 (A=Sr, Ce and B=Cu, Fe) nano-perovskite catalysts

Ali Farzi,Ali Tarjomannejad,Aligholi Niaei,Dariush Salari 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.9

Catalytic oxidation of toluene over perovskite-type oxides of the general formula LaMn1−xBxO3 (B=Cu, Fe and x=0, 0.3, 0.7) and La0.8A0.2Mn0.3B0.7O3 (A=Sr, Ce and B=Cu, Fe) was investigated, where the catalysts were synthesized by sol-gel auto combustion method. The catalysts were characterized by XRD, BET, H2-TPR, XPS, and SEM. Obtained XRD patterns confirmed the perovskites to be single-phase perovskite-type oxides. Specific surface areas of perovskites were obtained between 25-40m2/g. The perovskite catalysts showed high activity for the toluene oxidation. Based on the results, Fe-containing perovskite catalysts exhibited higher activity than Cu-containing perovskite catalysts. The substitution of Sr and Ce in A-site of the perovskite catalysts enhanced their activity for toluene oxidation. Among different synthesized catalysts in this research, La0.8Ce0.2Mn0.3Fe0.7O3 has the highest activity. Nearly complete elimination of toluene was achieved at 200 oC with this catalyst. Based on Langmuir–Hinshelwood mechanisms, kinetic studies were conducted on toluene oxidation, indicating LH-OS-ND (adsorption of reagents on same types of sites and non-dissociative adsorption of oxygen) as the most probable mechanism which could predict the experimental data with correlation coefficient of R2=0.9952.

Facile Synthesis of Ca-Doped LaCoO₃ Perovskite via Chemically Assisted Electrodeposition as a Protective Film on Solid Oxide Fuel Cell Interconnects

Park, Beom-Kyeong,Song, Rak-Hyun,Lee, Seung-Bok,Lim, Tak-Hyoung,Park, Seok-Joo,Park, Chong-Ook,Lee, Jong-Won The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.9

<P>Interconnects in solid oxide fuel cells (SOFCs) serve two essential roles, namely, cell-to-cell electrical connection and the separation of fuel and oxidant gases. It is of practical significance to develop a protective coating that is capable of improving the surface stability of metallic interconnects while maintaining their electrical properties. Perovskite-type oxides are recognized as promising materials for protective coatings; however, it is difficult to fabricate high-density films by conventional powder-sintering processes. In this paper, we report a facile electrodeposition-based approach to preparing perovskite oxide films on SOFC interconnects. A high density, adhesive Ca-doped LaCoO3 perovskite film of similar to 1.3 mu m thickness is directly formed on an SOFC interconnect through the 'chemically assisted electrodeposition' of hydroxide combined with the thermal conversion of hydroxide to oxide. In the proposed synthesis method, the electrodeposition parameters, such as solution composition and deposition time, have a strong influence on the composition, microstructure, and adhesion of the perovskite oxide film. The fabricated film exhibits outstanding performance as a protective coating for SOFC interconnects, as evidenced by a low area-specific resistance of 14.4 m Omega cm(2) at 800 degrees C and high stability during both continuous operation and repeated thermal cycling. (C) 2016 The Electrochemical Society. All rights reserved.</P>

Structure, chemical stability and electrical conductivity of perovskite La_0.6Sr_0.4M_0.3Fe_0.7O_{3−<i>δ</i>} (M=Co, Ti) oxides

Lu, Hui,Kim, Jong Pyo,Son, Sou Hwan,Park, Jung Hoon Elsevier 2010 Materials science and engineering B. Advanced Func Vol.166 No.2

<P><B>Abstract</B></P><P>The perovskite La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>M<SUB>0.3</SUB>Fe<SUB>0.7</SUB>O<SUB>3−<I>δ</I></SUB> (M=Co, Ti) powders have been synthesized by the citrate gel method. The structural and chemical stability of the La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>M<SUB>0.3</SUB>Fe<SUB>0.7</SUB>O<SUB>3−<I>δ</I></SUB> (M=Co, Ti) oxides were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. The electrical conductivities of the sintered La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>M<SUB>0.3</SUB>Fe<SUB>0.7</SUB>O<SUB>3−<I>δ</I></SUB> (M=Co, Ti) ceramics were measured. The results demonstrate the chemical stability in H<SUB>2</SUB>/helium (He) atmosphere of the La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>Ti<SUB>0.3</SUB>Fe<SUB>0.7</SUB>O<SUB>3−<I>δ</I></SUB> oxide is improved significantly compared to that of the La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>Co<SUB>0.3</SUB>Fe<SUB>0.7</SUB>O<SUB>3−<I>δ</I></SUB> oxide. The incorporation of Ti<SUP>3+/4+</SUP> ions in the perovskite structure can significantly stabilize the neighboring oxygen octahedral due to the stronger bonding strength, leading to the enhanced structural and chemical stability of the La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>Ti<SUB>0.3</SUB>Fe<SUB>0.7</SUB>O<SUB>3−<I>δ</I></SUB>. In addition, the perovskite La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>M<SUB>0.3</SUB>Fe<SUB>0.7</SUB>O<SUB>3−<I>δ</I></SUB> (M=Co, Ti) oxides possess much higher chemical stability in CO<SUB>2</SUB>/He atmosphere than that of Ba<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>0.8</SUB>Fe<SUB>0.2</SUB>O<SUB>3−<I>δ</I></SUB> oxide, in which the perovskite structure is destroyed completely in a flowing CO<SUB>2</SUB>-containing atmosphere.</P>

Boosted Perovskite Photodetector Performance Using Graphene as Transparent Electrode

M. Khaouani,H. Bencherif,A. Meddour 한국전기전자재료학회 2022 Transactions on Electrical and Electronic Material Vol.23 No.2

In this paper, a new perovskite photodetector based on Graphene/reduced Graphene oxide/Perovskite material system has been investigated. A rigorous study through design of high speed and high sensitivity photodetector has been conducted to achieve an optimum device performance. The proposed photodetector was studied using 3D Atlas Silvaco simulator with regard to dark current, energy band diagram, electric fi eld profi le, photo to dark current ratio (PDCR), responsivity, sensitivity and detectivity. Our fi ndings demonstrate the outstanding ability of the proposed Graphene electrode scheme to reduce the undesirable shadowing eff ect and enhance the collection mechanism. Besides, reduced graphene oxide interlayer with high conductivity plays a crucial role for high effi cient charge transportation. The proposed design displays 10 times photocurrent improvement when compared to the conventional design Au/TiO 2 /Perovskite photodetector. The proposed device displays a high value of responsivity of 340 A/W, a 100 GHz bandwidth with 10 μs transient response, and signifi cant PDCR of 646.4, high detectivity of 2.61 × 10 13 (Jones) and high sensitivity of 6.46 × 10 4 . In addition, the proposed photodetector shows ruggedness under high temperature condition. This modeling strategy is able to direct other researchers in the design and development of effi cient perovskite optoelectronic devices.

Three-dimensional arrangements of perovskite-type oxide nano-fiber webs for effective soot oxidation

Lee, C.,Jeon, Y.,Hata, S.,Park, J.I.,Akiyoshi, R.,Saito, H.,Teraoka, Y.,Shul, Y.G.,Einaga, H. Elsevier 2016 Applied catalysis. B, Environmental Vol.191 No.-

<P>Perovskite-type oxides have been widely applied in heterogeneous catalytic reactions, such as soot oxidation. However, a poor contact point between the catalyst and solid reactant (soot) often limits the catalytic performance. Here, we report La1-xSrxCo0.2Fe0.8O3-delta perovskite oxide catalysts with a unique three-dimensional (3D) fiber web structure that increases the high-contact area by trapping soot in the unique pore structure for effective catalytic activity. This feature was carefully analyzed using scanning transmission electron microscopy (STEM) tomography to investigate the location of the soot on the web. The structure of the web, with a thickness of approximately 55 mu m, indicated that the soot particles were caught by the 3D pores between the fibers. The relationship between the Sr amount and activate oxygen was also characterized by means of XPS. The results show that the Sr amount of 0.4 produced the highest amount of active oxygen species (O-) that are essential for soot oxidation reaction. The developed catalyst exhibited a good catalytic performance due to the optimized perovskite chemical structure and the greatly increased number of the contact points owing to the 3D inter-fiber spaces. Hence, our proposed approach is reasonable for application to real soot combustion processes and can also be easily extended to numerous other catalytic processes to enhance the catalytic activity. (C) 2016 Elsevier B.V. All rights reserved.</P>

Perovskite/polyethylene oxide composites: Toward perovskite solar cells without anti-solvent treatment

Lee, Seojun,Cho, Jung Sang,Kang, Dong-Won Elsevier 2019 Ceramics international Vol.45 No.17

<P><B>Abstract</B></P> <P>In this study, polyethylene oxide (PEO) is introduced into methylammonium lead iodide (MAPbI<SUB>3</SUB>) perovskite to replace the standard anti-solvent washing process of perovskite solar cells. By forming PEO-MAPbI<SUB>3</SUB> composites, we achieved controllability of the perovskite surface morphology. Furthermore, the PEO addition improved the electronic properties of the composites by suppressing the trap density of the MAPbI<SUB>3</SUB> perovskite. We observed a significant increase in the average power conversion efficiency (PCE) of the perovskite solar cells (PVSCs) from 0.24% to 7.25% using the proper PEO-perovskite composition ratio (1.5:1), based on their fabrication without any organic anti-solvent treatment. Moreover, the performance uniformity and outdoor stability were significantly enhanced by employing the composite. The proposed PEO-perovskite composite offers a promising pathway for the industrialization of PVSCs in terms of PCE, uniformity, stability, and feasibility—without involving current anti-solvent washing process.</P>

A Combinatorial Chemistry Method for Fast Screening of Perovskite-Based NO Oxidation Catalyst

Yoon, Dal Young,Lim, Eunho,Kim, Young Jin,Cho, Byong K.,Nam, In-Sik,Choung, Jin Woo,Yoo, Seungbeom American Chemical Society 2014 ACS Combinatorial Science Vol.16 No.11

<P>A fast parallel screening method based on combinatorial chemistry (combichem) has been developed and applied in the screening tests of perovskite-based oxide (PBO) catalysts for NO oxidation to hit a promising PBO formulation for the oxidation of NO to NO<SUB>2</SUB>. This new method involves three consecutive steps: oxidation of NO to NO<SUB>2</SUB> over a PBO catalyst, adsorption of NOx onto the PBO and K<SUB>2</SUB>O/Al<SUB>2</SUB>O<SUB>3</SUB>, and colorimetric assay of the NOx adsorbed thereon. The combichem experimental data have been used for determining the oxidation activity of NO over PBO catalysts as well as three critical parameters, such as the adsorption efficiency of K<SUB>2</SUB>O/Al<SUB>2</SUB>O<SUB>3</SUB> for NO<SUB>2</SUB> (α) and NO (β), and the time-average fraction of NO included in the NOx feed stream (ξ). The results demonstrated that the amounts of NO<SUB>2</SUB> produced over PBO catalysts by the combichem method under transient conditions correlate well with those from a conventional packed-bed reactor under steady-state conditions. Among the PBO formulations examined, La<SUB>0.5</SUB>Ag<SUB>0.5</SUB>MnO<SUB>3</SUB> has been identified as the best chemical formulation for oxidation of NO to NO<SUB>2</SUB> by the present combichem method and also confirmed by the conventional packed-bed reactor tests. The superior efficiency of the combichem method for high-throughput catalyst screening test validated in this study is particularly suitable for saving the time and resources required in developing a new formulation of PBO catalyst whose chemical composition may have an enormous number of possible variations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/acsccc/2014/acsccc.2014.16.issue-11/co5000344/production/images/medium/co-2014-000344_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/co5000344'>ACS Electronic Supporting Info</A></P>

Perovskite Co-free La_0.6Sr_0.4M_0.2Fe_0.8O_3-δ; (M=Cr or Ti) mixed-conductors: Preparation and characterization

Lu, H.,Kim, J.P.,Son, S.H.,Park, J.H. Elsevier 2009 Materials science and engineering B. Advanced Func Vol.163 No.3

The new Co-free La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>M<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3-δ</SUB>; (M=Cr or Ti) perovskite oxides have been successfully synthesized by the citrate acid complexing method. The La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>Co<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3-δ</SUB>; and as-synthesized Co-substituted La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>M<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3-δ</SUB>; (M=Cr or Ti) oxides all possess the rhombohedral perovskite-type structure. The structural stability, chemical reduction-tolerance ability (in a flowing 10% H<SUB>2</SUB>/helium stream) and sintering performance of the as-synthesized La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>M<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3-δ</SUB>; (M=Cr or Ti) oxides were studied by XRD, TGA/DSC and SEM. The results demonstrate the reduction-tolerance ability of the as-synthesized Co-free La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>M<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3-δ</SUB>; (M=Cr or Ti) oxides is improved significantly compared to that of the Co-containing La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>M<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3-δ</SUB>; (M=Co) oxide. The presence of Cr<SUP>3+/4+</SUP> or Ti<SUP>3+/4+</SUP> ions in the B-sites of the perovskite-type structure can further stabilize the neighboring oxygen octahedral (BO<SUB>6</SUB>) due to the stronger columbic attraction, leading to the enhanced stability of the as-synthesized Cr- or Ti-substituting perovskite Co-free oxides.