Enhancing the Intrinsic Activity and Stability of Perovskite Cobaltite at Elevated Temperature Through Surface Stress

Abstract

SOFC/SOEC) functioning at elevated temperature, [1][2][3][4] electrochemical water splitting in aqueous solution, [5][6][7] and advanced oxidation processes for water treatment. [8] However, perovskite-based materials synthesized via the conventional solid-state reaction methods typically show large particle size due to high sintering temperature, thus resulting in poor catalytic performance.To enhance the device performance, various techniques have been developed to synthesize perovskite-based oxide catalysts with nanostructure. [9][10][11][12][13][14][15][16] For instance, Chen et al. [17] synthesized a hierarchically porous nano network (Sm 0.5 Sr 0.5 CoO 3 -Gd 0.1 Ce 0.9 O 2-δ ) as a cathode of SOFC, which strongly enhanced the power density and stability of the devices. Similarly, Ahn et al. [13] reported that SOFC with Sm 0.5 Sr 0.5 CoO 3-δ nanofiber-based composite cathode showed a significantly lower area specific resistance compared to one with SSC powder cathode. Zhao et al. observed strongly boosted oxygen evolution reaction (OER) activity of PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF) nanotube in alkaline solution as they shrank the material size to tens of nanometers. [14] Although all these works demonstrate that nanostructure engineering can be an effective approach for improving the catalytic activity of perovskite-based oxide, the mechanism for the enhancement is still not fully understood. In most cases, the improved performance was attributed to Perovskite-based oxides attract great attention as catalysts for energy and environmental devices. Nanostructure engineering is demonstrated as an effective approach for improving the catalytic activity of the materials. The mechanism for the enhancement, nevertheless, is still not fully understood. In this study, it is demonstrated that compressive strain can be introduced into freestanding perovskite cobaltite La 0.8 Sr 0.2 CoO 3−δ (LSC) nanofibers with sufficient small size. Crystal structure analysis suggests that the LSC fiber is characterized by compressive strain along the ab plane and less distorted CoO 6 octahedron compared to the bulk powder sample. Accompanied by such structural changes, the nanofiber shows significantly higher oxygen reduction reaction (ORR) activity and better stability at elevated temperature, which is attributed to the higher oxygen vacancy concentration and suppressed Sr segregation in the LSC nanofibers. First-principle calculations further suggest that the compressive strain in LSC nanofibers effectively shortens the distance between the Co 3d and O 2p band center and lowers the oxygen vacancy formation energy. The results clarify the critical role of surface stress in determining the intrinsic activity of perovskite oxide nanomaterials. The results of this work can help guide the design of highly active and durable perovskite catalysts via nanostructure engineering.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202104144.

Gluing Ba0.5Sr0.5Co0.8Fe0.2O3−δ with Co3O4 as a cathode for proton-conducting solid oxide fuel cells

“…4b, c, indicates that the distance between O 2p and Co 3d (D 3d-2p ) decreases from 3.34 for BSCF to 1.59 for BSCF + Co 3 O 4 . Report has also indicated that the decreased D 3d-2p distance predicts the low energy formation of Vo [54], which agrees with the aforementioned E vo results. Furthermore, although D 3d-2p is usually regarded as a good indicator of the catalyst activity at room temperature [57] and is not widely used for SOFCs, a recent study indicates that one mechanism for H-SOFC cathode reactions also contains the formation of *O 2 , *OOH, *O and *OH adsorbates [58], which shows some similarities to the ORR procedure at room temperature [57].…”

“…4a shows the calculated configuration of the BSCF-Co 3 O 4 structure. Reports have indicated that the heterostructure could enhance the interface properties [54]. Therefore, the Vo formation energy (E vo ) at the BSCF-Co 3 O 4 interface was calculated, and the result indicates that the E vo at the BSCF-Co 3 O 4 interface is −2.98 eV, which is significantly lower than that for BSCF (−1.19 eV), suggesting that the formation of Vo is more favorable at the BSCF-Co 3 O 4 interface compared with BSCF.…”

Revealing the Impact of Steam Concentration on the Activity and Stability of Double-Perovskite Air Electrodes for Proton-Conducting Electrolysis Cells

“…The 3d 5/2 and 3d 3/2 peaks for Sr within a lattice (Sr lattice) were located at 131.7 and 133.4 eV, respectively, whereas the 3d 5/2 and 3d 3/2 peaks for an Sr non-lattice were at 133.7 and 135.4 eV. The intensity ratio and energy difference of the 3d 5/2 and 3d 3/2 peaks were set to be 1.5:1 and 1.7 eV, respectively. , Detailed fitting parameters and results are shown in Supporting Information Table S1. For the as-prepared PBSCF, the Sr non-lattice to Sr lattice ratio (Sr non-lattice/Sr lattice) was 0.728.…”

“…The intensity ratio and energy difference of the 3d 5/2 and 3d 3/2 peaks were set to be 1.5:1 and 1.7 eV, respectively. 29,30 Detailed fitting parameters and results are shown in Supporting Information Table S1. For the as-prepared PBSCF, the Sr non-lattice to Sr lattice ratio (Sr non-lattice/Sr lattice) was 0.728.…”

BaTb0.3Fe0.7O3−δ: a new proton-conductor-derived cathode for proton-conducting solid oxide fuel cells

“…Vo plays an essential role in oxygen-ion diffusion and oxygen reduction reaction (ORR) activity. 59–61 The improved Vo content in BTF is expected to facilitate the material's oxygen diffusion and exchange abilities. Fig.…”