Tailoring the Surface of Perovskite through In Situ Growth of Ru/RuO₂ Nanoparticles as Robust Symmetrical Electrodes for Reversible Solid Oxide Cells

Abstract

and chemical energies. Reversible solid oxide cells (RSOCs) have been attracting great attention due to their multiple functionalities and high potential efficiency, such as generating electricity as fuel cells (FC mode) and producing hydrogen as electrolysis cells (EC mode). [2] Generally, the traditional RSOCs consist of three different components, both fuel electrode and oxygen electrode, separated by a dense electrolyte. [3] Usually, the electrodes consist of different materials, in order to efficiently carry out the fuel oxidation reaction (FOR), oxygen reduction reaction (ORR), hydrogen evolution reaction, and oxygen evolution reaction (OER), respectively. [4] However, the range of necessary materials to provide these functions poses limitations on material selection and increases the complexity of manufacturing, operation, and maintenance, thus limiting applicability. Additionally, the long-term stability of RSOCs operated under high temperatures is still a challenge. [5] Especially, the interface between electrode and electrolyte is subjected to different conditions if the operation mode switched between FC and EC. [6] One approach to overcome some of the above limitations is to fabricate RSOCs using the same electrode material for both fuel electrode and oxygen electrode, in so-called symmetric solid oxide cells (SSOCs). [7] Such devices exhibit obvious advantages over current designs, including but not limited to lower cost, simpler fabrication process and minimizing interfacial problems among different cell components, possibly improvement on device lifetime and thus lower maintenance requirements. Considering that the fuel and oxygen electrodes operate in highly reducing and oxidizing environments, respectively, it is important to seek out suitable materials fulfilling the requirements applicable to both types of atmospheres for reversible SSOCs. [8] The materials should have high electronic and ionic conductivity, high electrochemical catalytic activity and durability in both oxidizing and reducing conditions. [14] To date, several redox-stable perovskite-type oxides have been considered for this role. [7-9] However, most of these have not been applied as both fuel and oxygen electrodes simultaneously for reversible SSOCs and the catalytic activity of these electrodes is still far from the requirements. Although numerous perovskite oxides can enhance the electrochemical activity via exsolved metallic nanoparticles on the surface, most of them can only be applied as catalysts in a reducing atmosphere. These nanoparticles cause serious performance degradation in oxidizing conditions due to the formation of low-conductive metal oxides. This poses a big challenge to the design of highly active catalysts of electrochemical devices, especially for symmetrical solid oxide cells. Herein, based on the strategy of exsolved metallic nanoparticles in A-site deficient perovskite, a unique and simple method is demonstrated for the synthesis of Ru/RuO 2 nanoparticles on the surface of perovskite oxide via in situ g...

Progress of Perovskites as Electrodes for Symmetrical Solid Oxide Fuel Cells

“…42 To enhance the catalytic activity toward hydrogen oxidation reaction (HOR), the strategy of in situ generation of uniformly distributed active metal nanoparticles from perovskite parents was explored. 43 The (La 0.8 Sr 0.2 ) 0.9 Sc 0.2 Mn 0.75 Ru 0.05 O 3−δ perovskite was designed to resolve Ru nanoparticles in situ in reducing the operation atmosphere (Figure 3a), which leads to a remarkable decrease in R p by a factor of 4.8 compared to the pristine sample at 800 °C in 5% H 2 /N 2 (Figure 3b). 44 To enhance the ORR activity, oxygen ion conductors like YSZ 45,46 and GDC 47,48 were employed to promote the oxygen transport or oxygen surface exchange kinetics by direct mixing or infiltrating processes.…”

Phase transition with in situ exsolution nanoparticles in the reduced Pr0.5Ba0.5Fe0.8Ni0.2O3−δ electrode for symmetric solid oxide cells

“…Therefore the development of highly active materials is crucial for the progress of SSOCs. Ti-, 13,14 Cr-, 11,15 Mn-, 16,17 Fe-, 18,19 and Co-based 20,21 perovskite oxides have been studied as electrocatalysts for SSOCs. Due to the stable electronic conguration (3d 5 ) of Fe 3+ and the mixedvalence state of Fe, 22 Fe-based perovskites are more durable than Co-and Mn-based perovskites, and also have better electrocatalytic activity than Ti-and Cr-based perovskites.…”

“…10 Besides, in this case there is only one type of electrode–electrolyte interface, minimizing the risk of chemical and thermomechanical interfacial incompatibility. 11 Moreover, sulfur poisoning and carbon deposition can be easily removed through gas conversion when the reducing and oxidizing atmospheres are interchanged. Therefore, these devices can be used to rapidly switch between SOFC and SOEC modes.…”

In Situ Growth of Ru/RuO2 Nanoparticle-Modified (PrBa)0.95Mn1.9Ru0.1O5+δ as a High-Performance Electrode for Symmetrical Solid Oxide Fuel Cells

“…In the coming years, a new structure of symmetrical SOFCs (SSOFCs) have obtained significant interest from researchers around the world, where the same materials are employed as oxygen and fuel electrodes simultaneously . It is promising for SSOFCs to replace the traditional SOFCs as a result of several advantages . First, with this kind of design, only one sintered step is required for symmetrical electrodes in the manufacture process, which reduces the fabrication costs considerably .…”

“…11 It is promising for SSOFCs to replace the traditional SOFCs as a result of several advantages. 12 First, with this kind of design, only one sintered step is required for symmetrical electrodes in the manufacture process, which reduces the fabrication costs considerably. 13 Additionally, the incompatibility issues among components of cells can also be relieved when the same material is applied as both oxygen and fuel electrodes.…”