The development of highly active cathode materials is essential to lower the operating temperature of solid oxide fuel cells (SOFCs), where the slow kinetics of the oxygen surface exchange on the cathode surface limits the efficiency of SOFCs at intermediate temperatures (500–750 °C).^[ Reference Shao and Haile ^{1 ,} Reference Steele and Heinzel ^{2 ]} Current cathode materials such as La_1−x Sr _x MnO_3−δ (LSM₁₁₃)^[ Reference da Conceicao, Silva, Ribeiro and Souza ^{3 –} Reference Ioroi, Hara, Uchimoto, Ogumi and Takehara ^{5 ]} with high electronic conductivity but low ionic conductivity^[ Reference Adler ^{6 ]} are inadequate for the usage in the intermediate temperature range due to insufficient surface activity.

La_1−x Sr _x Fe_1−y Co _y O_3−δ (LSCF₁₁₃), which has beneficial materials properties such as high ionic and electronic conductivity,^[ Reference Wang, Katsuki, Dokiya and Hashimoto ^{7 ]} and fast oxygen surface exchange,^[ Reference Katsuki, Wang, Dokiya and Hashimoto ^{8 ]} therefore, has been developed as one of the most promising commercial cathode materials for intermediate temperature SOFCs. In particular, a solution infiltration process, in which a phase transition occurs from a liquid into a solid has been widely used to further enhance the surface activity of LSCF₁₁₃.^[ Reference Liu, Ding, Blinn, Li, Nie and Liu ^{9 –} Reference Zhu, Ding, Li, Lu, Su and Zhen ^{12 ]} Utilizing infiltrated LSM₁₁₃ coatings, it has been shown the enhanced electrocatalytic activity of LSCF₁₁₃ cathodes.^[ Reference Lynch, Yang, Qin, Choi, Liu, Blinn and Liu ^{11 ,} Reference Zhu, Ding, Li, Lu, Su and Zhen ^{12 ]} Infiltrated La_0.4875Ca_0.0125Ce_0.5O_2−δ (LCC)^[ Reference Liu, Ding, Blinn, Li, Nie and Liu ^{9 ]} and Sm_0.5Sr_0.5CoO_3−δ (SSC)^[ Reference Lou, Wang, Liu, Yang and Liu ^{10 ]} coatings have also been used for better stability and activity of LSCF₁₁₃ electrodes. Although many studies have shown the enhanced cathodic performance of LSCF₁₁₃ by surface modification through a solution-based infiltration process, the origin responsible for the enhanced stability and activity of decorated LSCF₁₁₃ cathode is poorly understood.

Ruddlesden-Popper (RP) phases (A ₂ BO₄) have been utilized as a material for the La_1−x Sr _x CoO_3−δ (LSC₁₁₃) surface modification, which results in the enhanced surface activity of LSC₁₁₃ significantly due to the formation of heterostructured oxide interfaces.^[ Reference Crumlin, Ahn, Lee, Mutoro, Biegalski, Christen and Shao-Horn ^{13 –} Reference Sase, Hermes, Yashiro, Sato, Mizusaki, Kawada, Sakai and Yokokawa ^{18 ]} Using well-defined epitaxial thin film systems, remarkably enhanced oxygen surface exchange kinetics (up to ~2 orders of magnitude) of LSC₁₁₃ has been reported by decorating (La_0.5Sr_0.5)₂CoO_4±δ (LSC₂₁₄) phase on the LSC₁₁₃ surface.^[ Reference Crumlin, Ahn, Lee, Mutoro, Biegalski, Christen and Shao-Horn ^{13 ,} Reference Crumlin, Mutoro, Ahn, la O, Leonard, Borisevich, Biegalski, Christen and Shao-Horn ^{19 ]} Coherent Bragg rod analysis (COBRA) and density functional theory (DFT) have suggested that the enhanced oxygen surface exchange kinetics may be attributed to the Sr segregation at the LSC₂₁₄–LSC₁₁₃ interface and the LSC₂₁₄ surface, resulting from a large driving force for A-site cation interdiffusion across the heterostructured interface.^[ Reference Feng, Crumlin, Hong, Lee, Mutoro, Biegalski, Zhou, Bluhm, Christen and Shao-Horn ^{14 ,} Reference Gadre, Lee and Morgan ^{15 ,} Reference Feng, Yacoby, Gadre, Lee, Hong, Zhou, Biegalski, Christen, Adler, Morgan and Shao-Horn ^{20 ]} In addition, the enhanced activity of LSC₁₁₃ may also be attributed to the stabilized LSC₁₁₃ surface by LSC₂₁₄ phase, which suppresses the formation of Sr-enriched secondary particles on the LSC₁₁₃ surface after a long-time annealing.^[ Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ]} However, the heterostructured oxide interfaces formed by decorating LSC₂₁₄ on LSCF₁₁₃ perovskites have shown negligible enhancement (up to two times) of the oxygen surface exchange kinetics of LSCF₁₁₃,^[ Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ]} which can be attributed to no further increase in Sr concentration at the surface of LSCF₁₁₃ induced by LSC₂₁₄ decoration. While growing a more Sr-rich LSC₂₁₄ on LSCF₁₁₃ might yield enhancement due to the high oxygen surface exchange kinetics of LSC₂₁₄ (x _Sr > 1.0),^[ Reference Gadre, Lee and Morgan ^{15 ,} Reference Nitadori, Muramatsu and Misono ^{21 ]} such an approach is inhibited by difficulties in the synthesis of RP phase with high Sr substitution.^[ Reference Sase, Hermes, Nakamura, Yashiro, Sato, Mizusaki, Kawada, Sakai, Yamaji, Horita, Yokokawa, Eguchi, Singhai, Yokokawa and Mizusaki ^{22 ,} Reference Shinomori, Kawasaki and Tokura ^{23 ]}

In this study, we have developed the heterostructured oxide decoration on LSCF₁₁₃, which leads to the enhancement of the surface activity of the LSCF₁₁₃. Utilizing pulsed laser deposition (PLD), we employ two different types of surface decorations on the epitaxial LSCF₁₁₃ thin films, which are the single-layer decoration of mixed LSC₂₁₄ and LSC₁₁₃ and the double-layer decoration of stacked LSC₂₁₄ and LSC₁₁₃. These structures stabilize the LSC₁₁₃ phase, providing sufficient Sr sources and thermodynamic driving force for the Sr interdiffusion between LSC₂₁₄ and LSC₁₁₃. Electrochemical impedance spectroscopy (EIS) study reveals that the oxygen surface exchange coefficients (k ⁱ) of the LSCF₁₁₃ thin films can be significantly enhanced up to ~1.5 orders of magnitudes higher than those of the undecorated LSCF₁₁₃ by the heterostructured oxide interface engineering. In addition, the LSC₁₁₃ with higher Sr content relative to the LSC₂₁₄ single phase in both single-layer and double-layer decoration leads to higher enhancement in the surface exchange kinetics of the LSCF₁₁₃, which suggests that the enhancement of the surface exchange kinetics of the LSCF₁₁₃ can be attributed to an increase of Sr concentration on the multiphase heterostructured interface.

PLD was used to deposit the epitaxial ~65 nm LSCF₁₁₃ thin films with the ~3 nm single-layer decoration of mixed LSC₂₁₄ and LSC₁₁₃ [Fig. 1(a)] and the double-layer decoration of stacked ~3 nm LSC₂₁₄ and ~0.5 nm LSC₁₁₃ [Fig. 1(b)] on an yttria-stabilized zirconia (YSZ) (001) substrate with a Gd-doped ceria (GDC) buffer layer. Out-of-plane x-ray diffraction (XRD) results [Figs. 1(c) and 1(d)] of the undecorated LSCF₁₁₃, LSC₂₁₄-decorated LSCF₁₁₃, the LSCF₁₁₃ with the single-layer decoration of mixed LSC₂₁₄ and LSC₁₁₃ thin films, and the LSCF₁₁₃ with the double-layer decoration of stacked LSC₂₁₄ and LSC₁₁₃ thin films clearly show the presence of the (00l)_pc (l is integer) peaks of LSCF₁₁₃ and (00l)_cubic (l is even) peaks of GDC and YSZ, indicating that the LSCF₁₁₃ film was grown epitaxially with the following epitaxial relationships: (001)_pcLSCF₁₁₃//(001)_cubicGDC//(001)_cubicYSZ (where “pc” denotes the pseudocubic notation). With higher Sr content of LSC₁₁₃ in the single- and double-layer decorations, the (00l)_tetra. (l is the integer) peaks of LSC₂₁₄ become visible, which represents (001)_tetra.LSC₂₁₄//(001)_pcLSCF₁₁₃//(001)_cubicGDC//(001)_cubicYSZ. The subscript “tetra.” denotes the tetragonal notation.^[ Reference Lee, Grimaud, Crumlin, Mezghani, Habib, Feng, Hong, Biegalski, Christen and Shao-Horn ^{24 ,} Reference Lee, Lee, Grimaud, Hong, Biegalski, Morgan and Shao-Horn ^{25 ]} Off-normal phi-scan analysis of the undecorated LSCF₁₁₃ and LSC₂₁₄-decorated LSCF₁₁₃ films shows that LSC₂₁₄ {103}_tetra., LSCF₁₁₃ {202}_pc, GDC {202}_cubic, and YSZ {202}_cubic have strong peaks with fourfold cubic symmetry (Fig. S1†). This reveals the in-plane crystallographic relationships between GDC and YSZ (a cube-on-cube alignment), LSCF₁₁₃ and GDC (an in-plane 45° rotation with [100]_pcLSCF₁₁₃//[110]_cubicGDC//[110]_cubicYSZ), and LSCF₁₁₃ and LSC₂₁₄ (no rotation with [100]_pcLSCF₁₁₃//[100]_tetra.LSC₂₁₄). Similar to our previous studies,^[ Reference Crumlin, Ahn, Lee, Mutoro, Biegalski, Christen and Shao-Horn ^{13 ,} Reference Feng, Crumlin, Hong, Lee, Mutoro, Biegalski, Zhou, Bluhm, Christen and Shao-Horn ^{14 ,} Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ,} Reference Crumlin, Mutoro, Ahn, la O, Leonard, Borisevich, Biegalski, Christen and Shao-Horn ^{19 ]} the relaxed lattice parameters, â of the epitaxial LSCF₁₁₃ films with and without surface decoration in this study at room temperature did not change significantly, ranging from 3.898–3.904 Å (Table S1†). As shown in Table S1†, both in-plane and out-of-plane strains of LSCF₁₁₃ films were not strongly influenced by the surface decoration, which is supported by the fact that the lattice constant of LSC₂₁₄ (a _tetra. ≈ 3.819 Å for LSC₂₁₄ bulk^[ Reference James, Tedesco, Cassidy, Colella and Smythe ^{26 ]}) is very close to that of LSCF₁₁₃ (a _pc ≈ 3.885 Å for the LSCF₁₁₃ bulk^[ Reference Tai, Nasrallah, Anderson, Sparlin and Sehlin ^{27 ]}) and LSC₁₁₃ (a _pc ≈ 3.854 Å for the LSC₁₁₃ bulk^[ Reference van Doorn and Burggraaf ^{28 ]}). This observation is further supported by our recent work,^[ Reference Feng, Crumlin, Hong, Lee, Mutoro, Biegalski, Zhou, Bluhm, Christen and Shao-Horn ^{14 ]} where the LSC₂₁₄ decoration has no influence on the in-plane and out-of-plane strains of the epitaxial LSC₁₁₃ films at elevated temperatures. Details about deposition, lattice parameter calculation, and high-resolution XRD of LSC₂₁₄-decorated LSC₁₁₃ film can be found in the ESI†.

Figure 1. Schematic representation of (a) the LSCF₁₁₃ with single-layer decoration of mixed LSC₂₁₄ and LSC₁₁₃, and (b) with double-layer decoration of stacked LSC₂₁₄ and LSC₁₁₃ epitaxial thin films. High-resolution XRD analysis of (c) the ~65 nm LSCF₁₁₃ reference (green), the ~3 nm LSC₂₁₄-decorated LSCF₁₁₃ (yellow), and the LSCF₁₁₃ with ~3 nm single-layer decorations of mixed LSC₂₁₄ and LSC82₁₁₃ (blue), LSC64₁₁₃ (orange), and LSC46₁₁₃ (red), and (d) the ~65 nm LSCF₁₁₃ reference (green), the ~3 nm LSC₂₁₄-decorated LSCF₁₁₃ (yellow), and the LSCF₁₁₃ with double-layer decorations of stacked ~3 nm LSC₂₁₄ and ~0.5 nm LSC82₁₁₃ (blue), ~0.5 nm LSC64₁₁₃ (orange), and ~0.5 nm LSC46₁₁₃ (red) epitaxial thin films on (001) YSZ substrates with GDC buffer layer. YSZ substrate and GDC peaks are indicated with pounds (#) and asterisks (*), respectively.

EIS results of geometrically well-defined microelectrodes (200 µm in diameter), measured at 550 °C are shown in Fig. 2. These microelectrodes were fabricated by photolithography and acid etched for the epitaxial LSCF₁₁₃ thin films with LSC₂₁₄ decoration and single-layer decorations of mixed LSC₂₁₄ and three different Sr contents of LSC₁₁₃ (Sr = 0.2, 0.4, and 0.6). The predominant semicircle was found to increase with decreasing oxygen partial pressure [Fig. 2(a)], where EIS data of all samples used in this study showed nearly perfect semicircle impedances.^[ Reference Adler ^{6 ]} Considering the fact that the film thicknesses are much smaller than the critical thickness for bulk transport limitation (estimated to 3.28 µm for bulk LSCF₁₁₃ at 550 °C^[ Reference Steele and Bae ^{29 ]}), the oxygen partial pressure [p(O₂)]-dependent impedance responses suggest that the oxygen surface exchange kinetics governs the oxygen electrocatalysis on the film surface. In Fig. 2(b), the real part of the impedance of the predominant semicircle decreased with increasing Sr content of LSC₁₁₃ in the single-layer decoration of mixed LSC₂₁₄ and LSC₁₁₃, where the oxygen surface exchange coefficient (k^q ) of the LSCF₁₁₃ with mixed LSC₂₁₄ and La_0.4Sr_0.6CoO_3−δ (LSC46₁₁₃) decoration was found to be ~7 times higher than that of undecorated LSCF₁₁₃ and LSC₂₁₄-decorated LSCF₁₁₃. This observation indicates that higher Sr content in mixed LSC₂₁₄ and LSC₁₁₃ decoration can lead to higher surface exchange kinetics of the LSCF₁₁₃.

Figure 2. EIS results of microelectrodes (200 µm in diameter) for the epitaxial LSCF₁₁₃ thin films with LSC₂₁₄ decoration, and single-layer decorations of mixed LSC₂₁₄ and LSC₁₁₃ on YSZ (001) with a GDC buffer layer at 550 °C. (a) Nyquist plot at 550 °C as a function of oxygen partial pressure, p (0₂), of the LSCF₁₁₃ thin films with single-layer decoration of mixed LSC₂₁₄ and LSC46₁₁₃. (b) Nyquist plot at 550 °C with an 1 atm of p(0₂) of the LSCF₁₁₃ (green), the LSC₂₁₄-decorated LSCF₁₁₃ (yellow), and the LSCF₁₁₃ with ~3 nm single-layer decoration of mixed LSC₂₁₄ and LSC82₁₁₃ (blue), LSC64₁₁₃ (orange), and LSC46₁₁₃ (red) thin films. (c) p(0₂) dependency of the surface exchange coefficients (k < l) of the LSCF₁₁₃ (green), the LSC₂₁₄-decorated LSCF₁₁₃ (yellow), and the LSCF₁₁₃ with ~3 nm single-layer decoration of mixed LSC214 and LSC82₁₁₃ (blue), LSC64₁₁₃ (orange), and LSC46₁₁₃ (red) thin films. All EIS spectra were collected at 550 °C.

To further investigate the effect of Sr concentration in the mixed LSC₂₁₄ and LSC₁₁₃ phase on the surface exchange kinetics of the LSCF₁₁₃, a different ratio between LSC₂₁₄ and LSC46₁₁₃ was applied for decorating the surface of the LSCF₁₁₃. EIS data collected from the LSCF₁₁₃ with and without the single-layer decoration of mixed LSC₂₁₄ and LSC46₁₁₃ thin films at 550 °C with an p(O₂) of 1 atm is shown in Fig. 3(a). It is noted that the k^q values of the LSCF₁₁₃ with 75% of LSC₂₁₄ and 25% of LSC46₁₁₃ decoration were found to be ~1.1 orders of magnitude higher than those of the LSCF₁₁₃ with and without LSC₂₁₄ decoration, as shown in Fig. 3(b). To understand these changes we consider if the decorations may lead to the enhancement of Sr in the LSCF₁₁₃ surface, which would be expected to increase the oxygen 2p band center relative to the Fermi level,^[ Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ]} which in turn is expected to correlate with the enhancement of the oxygen surface exchange kinetics.^[ Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ,} Reference Feng, Yacoby, Gadre, Lee, Hong, Zhou, Biegalski, Christen, Adler, Morgan and Shao-Horn ^{20 ,} Reference Lee, Kleis, Rossmeisl, Shao-Horn and Morgan ^{30 ]} In the case of the LSC₂₁₄ decorated LSCF₁₁₃, it has been proposed that low enhancement is observed because there is a negligible change of the surface Sr concentration at the heterostructured interface due to the initially high Sr surface concentration (~100%) of the stable LSCF₁₁₃ (001) surface. This high Sr concentration cannot be easily increased. In contrast, the addition of the LSC₁₁₃ phase into the LSC₂₁₄ can provide the increased Sr content in LSC₂₁₄ and associated thermodynamic driving force for Sr interdiffusion from the LSC₁₁₃ into the LSC₂₁₄. We propose that this driving force is large enough to result in higher Sr concentration in the surface decoration layer of mixed LSC₂₁₄ and LSC₁₁₃ on the LSCF₁₁₃ surface. Accordingly, this Sr enrichment is expected to uplift the oxygen 2p band center (relative to the Fermi level) of the LSCF₁₁₃ interface layer and enhance the oxygen exchange kinetics of the LSCF₁₁₃, as reported previously.^[ Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ]} Interestingly, the enhancement in the surface exchange kinetics of the LSCF₁₁₃ was found to decrease with increasing the LSC46₁₁₃ ratio in the LSC₂₁₄ phase. This can be explained by the fact that the LSC₂₁₄ phase becomes unstable with increasing LSC46₁₁₃, which can be supported by the reduced intensity of LSC₂₁₄ (00l)_tetra. peak in Fig. S2†. Although a detailed study of the electronic structure changes is needed, the enhanced Sr concentration in the LSC₂₁₄ by mixing with LSC₁₁₃ may be responsible for enhancing the surface exchange kinetics of the LSCF₁₁₃.

Figure 3. EIS results of microelectrodes (200 µm in diameter) for the epitaxial LSCF₁₁₃ thin films with LSC₂₁₄ decoration, and single-layer decorations of mixed LSC₂₁₄ and LSC46₁₁₃ on YSZ (001) with a GDC buffer layer at 550 °C. (a) Nyquist plot at 550 °C with an 1 atm of p(0₂) of the LSCF₁₁₃ (green), the LSC₂₁₄-decorated LSCF₁₁₃ (yellow), and the LSCF₁₁₃ with ~3 nm single-layer decoration of mixed LSC₂₁₄ and LSC64₁₁₃ (75%:25%) (dark red), LSC₂₁₄ and LSC64₁₁₃ (50%:50%) (red), and LSC₂₁₄ and LSC64₁₁₃ (25%:75%) (light red) thin films. (b) p(0₂) dependency of kG calculated from EIS spectra collected at 550 °C of the LSCF₁₁₃ (green), the LSC₂₁₄-decorated LSCF₁₁₃ (yellow), and the LSCF₁₁₃ with ~3 nm single-layer decoration of mixed LSC₂₁₄ and LSC64₁₁₃ (75%:25%) (dark red), LSC₂₁₄ and LSC64₁₁₃ (50%:50%) (red), and LSC₂₁₄ and LSC64₁₁₃ (25%:75%) (light red) thin films. Inset shows a hypothetical model: enhancement of the Sr content at the top surface of the LSCF₁₁₃ due to adding LSC₁₁₃ to LSC₂₁₄.

Figure 4(b) shows the k^q values of the LSCF₁₁₃ with double-layer decoration of stacked LSC₂₁₄ and three different Sr contents of LSC₁₁₃ (LSC82₁₁₃, LSC64₁₁₃, and LSC46₁₁₃) thin films, extracted from the EIS data [Fig. 4(a)]. As shown in Fig. 4(b), the k^q values of the LSCF₁₁₃ thin films were found to change with the additional LSC₁₁₃ phase between the LSCF₁₁₃ and LSC₂₁₄, which can be attributed to a change in the Sr concentration at the multiphase heterostructured interface. We hypothesize that the added LSC₁₁₃ phase provides sufficient Sr sources for surface Sr redistribution between LSC₁₁₃ and LSC₂₁₄, which results in increased Sr segregation on the LSCF interface layer. This hypothesis is consistent with our previous ab initio DFT calculations,^[ Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ]} which found that the thermodynamic driving force for Sr interdiffusion from La_0.625Sr_0.375Co_0.25Fe_0.75O₃ to (La_0.5Sr_0.5)₂CoO₄ (−0.12 eV) is much weaker than that from La_0.75Sr_0.25CoO₃ to (La_0.5Sr_0.5)₂CoO₄ (−0.7 eV). This driving force is likely responsible for different enhancements in the surface Sr content in the LSCF₁₁₃ films upon LSC₂₁₄ decoration, resulting in different surface exchange kinetics.

Figure 4. EIS results of microelectrodes (200 µm in diameter) for the epitaxial LSCF₁₁₃ thin films with LSC₂₁₄ decoration, and double-layer decorations of stacked LSC₂₁₄ and LSC₁₁₃ on YSZ (001) with a GDC buffer layer at 550 °C. (a) Nyquist plot at 550 °C with an 1 atm of p(0₂) of the LSCF₁₁₃ (green), the LSC₂₁₄-decorated LSCF₁₁₃ (yellow), and the LSCF₁₁₃ with double-layer decoration of stacked ~3 nm LSC₂₁₄ and ~0.5 nm LSC82₁₁₃ (blue), ~0.5 nm LSC64₁₁₃ (orange), and ~0.5 nm LSC46₁₁₃ (red) thin films. (b) p(0₂) of the k^q calculated from EIS spectra collected at 550 °C of the LSCF₁₁₃ (green), the LSC₂₁₄-decorated LSCF₁₁₃ (yellow), and the LSCF₁₁₃ with double-layer decoration of stacked ~3 nm LSC₂₁₄ and ~0.5 nm LSC82₁₁₃ (blue), ~0.5 nm LSC64₁₁₃ (orange), and ~0.5 nm LSC46₁₁₃ (red) thin films. Inset shows a hypothetical model: enhancement of the Sr content at the interface between the LSCF₁₁₃ and the LSC₂₁₄ phase due to an increase in the Sr interdiffusion from LSC₁₁₃ to LSC₂₁₄.

LSCF₁₁₃ with the double-layer decoration of stacked LSC₂₁₄ and LSC46₁₁₃ shows significantly higher k^q values up to ~1.5 orders of magnitude relative to the undecorated LSCF₁₁₃ and LSC₂₁₄-decorated LSCF₁₁₃. The enhancement can be attributed to Sr segregation at the interface between LSC₂₁₄ and LSC46₁₁₃ and on the LSC₂₁₄ surface at the expense of Sr in LSC46₁₁₃ in the double-layer decoration considering markedly enhanced activity of LSC₂₁₄-decorated LSC82₁₁₃ in the previous work.^[ Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ]}

In conclusion, we demonstrate that the oxygen surface exchange kinetics of the (001)-oriented epitaxial LSCF₁₁₃ thin films can be markedly improved by the advanced heterostructured oxide interface engineering using the single-layer decoration of mixed LSC₂₁₄ and LSC₁₁₃ and double-layer decoration of stacked LSC₂₁₄ and LSC₁₁₃. This result extends previous results,^[ Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ]} showing enhancement from decoration of LSC₂₁₄ on LSC₁₁₃ to the LSCF₁₁₃ material, which is of significantly more interest for commercial applications than LSC₁₁₃. The oxygen surface exchange coefficients of the LSCF₁₁₃ with single-layer decoration of mixed LSC₂₁₄ and LSC₁₁₃ are ~1.1 orders of magnitude greater than those of the undecorated LSCF₁₁₃ and LSC₂₁₄-decorated LSCF₁₁₃. In addition, the oxygen surface exchange coefficients of the LSCF₁₁₃ with double layer decoration of stacked LSC₂₁₄ and LSC₁₁₃ are ~1.5 orders of magnitude higher than those of the undecorated LSCF₁₁₃ with and without LSC₂₁₄ decoration. The previous work^[ Reference Lee, Lee, Hong, Biegalski, Morgan and Shao-Horn ^{17 ]} suggests a strong correlation between the O 2p band center and surface exchange kinetics, where surface Sr segregation in the perovskite structure and associated O 2p band uplift could increase the surface exchange rate. Therefore, we hypothesize that the decoration on the surface of LSCF₁₁₃ provides Sr segregation at the interface LSC₂₁₄ and LSC₁₁₃ and on the surface of LSC₂₁₄, which can uplift in the position of the O 2p band center relative to Fermi energy of the LSCF interface layer in comparison to that of the LSCF₁₁₃ surface. This work illustrates that heterostructured oxide interface engineering is a strategy, which can enhance multiple types of active oxide materials. Such approaches could potentially be utilized in the infiltration process for decorating cathodes to enhance the performance of SOFCs.