Novel in situ method (vacuum assisted electroless plating) modified porous cathode for solid oxide fuel cells
Introduction
Electroless plating (EP) is widely used in many areas, such as magnetic disk-drive heads, NMR microcoils, and micro/nanoelectronic devices [1]. It has been successfully used to deposit metals on variety of surface (e.g., Si/SiO2, glass [2], polyimide [3]), both two-dimensional (2D) and three-dimensional (3D) films [4]. Besides that, the most important characteristic for electroless plating is its in situ feature [4], [5]. Here, a novel modified EP method named vacuum assisted electroless plating (VA–EP) is presented to deposit metals into the micro-porous structure, which is operated under a vacuum condition (<20 kPa). Air within the micro-porous of the sample is deflated before dropping into the solution, which enables the immersed solution to infilter into the micro-porous structure easily to form a homogeneous deposition, preventing the surface from covering with the excess deposition. This method focuses on modifying the already-given micro-porous structure. Most important, the convenient and economic character of this method is obvious in preparing catalyst in a porous support.
To demonstrate the advantage of VA–EP, the mixed ionic/electronic conductors (MIECs) Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is selected as the already-given porous support, which is an excellent cathode material for IT–SOFCs [6], [7]. We expect the deposition of silver into BSCF (VA–EPA–BSCF) can further improve the electrochemical performance by means of enhancing the electronic conductivity, as well as the catalysis ability of oxygen reaction.
Section snippets
Sample preparation
Detailed synthesis of BSCF, electrolyte material Ce0.8Sm0.2O1.9 (SDC) and anode materials Ni–SDC powders for this investigation were available elsewhere [8], [9], [10]. Then a half cell with symmetric cathodes (0.28 cm2) was prepared with BSCF fabricated on both sides of the SDC electrolyte disk (sintered at 1400 °C for 4 h) and sintered at 1000 °C for 4 h. The cathode (0.20 cm2) fabricated on an anode supported cell was sintered at 1000 °C for 4 h as well. Formaldehyde and ammonia were used as
Microstructure characterization
Fig. 1a shows a cross-sectional morphology of the symmetrical cell, in which fine BSCF particles are fabricated in a porous structure and adheres well to the dense electrolyte SDC. Fig. 1b shows the BSCF particles have a diameter of 1 μm by average. Fig. 1c and d reveal BSCF cathode modified by the VA–EPA method. Both of the cathodes have a thickness of 12 μm. A homogeneous, slim and translucent silver network throughout the porous BSCF layer can be seen, which meet our expectation compared with
Conclusions
The novel vacuum assisted electroless plating method successfully introduced homogeneous silver network into the porous BSCF cathode. The XPS results showed the silver had different chemical states in the original and inner surface. Both the impedance spectra results and the maximum power densities indicated the VA–EPA–BSCF cathode exhibited much better performance than the pure BSCF one. More important, this modification method would be a promising one for other porous materials in other
Acknowledgements
The authors gratefully acknowledge the financial supports from the Ministry of Science and Technology of China under contract no. 2007AA05Z139. The authors were also grateful to Dianlong Wang and Hua Jin (Harbin Institute of Technology) for their friendly help.
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Developing an ultrafine Ba<inf>0.5</inf>Sr<inf>0.5</inf>Co<inf>0.8</inf>Fe<inf>0.2</inf>O<inf>3-δ</inf> cathode for efficient solid oxide fuel cells
2022, Ceramics InternationalCitation Excerpt :Numerous strategies have effectively promoted the surface exchange ability of BSCF. These strategies include decoration of the surface of BSCF with active promoters such as Ag and (La, Sr)MnO3 (LSM) [12–19], formation of a composite with a second phase such as doped ceria [20–24], doping at the A or B-sites of BSCF [25–28], and utilisation of a grain growth inhibitor [29]. A straightforward strategy is to maximise the surface area of BSCF by preparing it in the form of an ultrafine powder.
Manufacturing method of BSCF cathode for low-temperature solid oxide fuel cell-A review
2022, Materials Today: ProceedingsAg decorated (Ba,Sr)(Co,Fe)O<inf>3</inf> cathodes for solid oxide fuel cells prepared by electroless silver deposition
2013, International Journal of Hydrogen EnergyCitation Excerpt :Compared to the inhomogeneous distribution of nanoparticles introduced by conventional impregnation approaches, e.g., in the case of (Gd,Ce)O2 (GDC)-infiltrated LSM cathodes [58], all electrodes retain the highly porous microstructure regardless of the Ag loading. As discussed in our previous work, the oxidation states of Ag within Ag@BSCF prepared by electroless deposition and Ag/BSCF by infiltration are different [51]. The Ag in Ag@BSCF exhibits different chemical states in the near surface region (Ag2O) and in the bulk (Ag), whereas the Ag in Ag/BSCF presents only the oxidation state (Ag2O).
Evaluation of (Ba <inf>0.5</inf>Sr <inf>0.5</inf>) <inf>0.85</inf>Gd <inf>0.15</inf>Co <inf>0.8</inf>Fe <inf>0.2</inf>O <inf>3-δ</inf> cathode for intermediate temperature solid oxide fuel cell
2012, Ceramics InternationalCitation Excerpt :A high electrical conductivity for a cathode facilitates fast electron transfer and thereby improves electrochemical activity for oxygen reduction reaction on the cathode. Researchers have made efforts to enhance the electrical conductivity of BSCF by addition of components with a higher conductivity, such as Ag network within the electrode [17,18] and combining BSCF with other cathode materials that have a higher conductivity such as (La,Sr)MnO3 and (Sm,Sr)CoO3 [19,20]. Li et al. [21–23] reported that the introduction of rare earths (La, Sm, and Nd) in the A-site of BSCF resulted in both enhanced electrical conductivity and electrochemical behavior toward oxygen reduction reaction.