Enhancing Cr-tolerance Ability of Double Perovskite Cathodes through Configuration Entropy Engineering

doi:10.15541/jim20240542

Abstract

Abstract:

Solid oxide fuel cells (SOFCs) are a kind of highly efficient and clean power generation devices whose cathode performance is critically important for the commercial application of the entire cell. Cation segregation on the surface of cathodes significantly affects the performance and operational stability. The double perovskite oxide PrBa_0.8Ca_0.2Co₂O₅₊_δ (PBCC), a highly active cathode, still suffers from serious surface segregation and insufficient Cr-tolerance ability. In order to improve the stability of cathode, an A-site medium-entropy double perovskite oxide Pr_0.6La_0.1Nd_0.1Sm_0.1Gd_0.1Ba_0.8Ca_0.2Co₂O₅₊_δ (ME-PBCC) derived from PBCC was prepared, and its segregation behavior in Cr-containing atmosphere was systematically investigated. Compared with traditional PBCC cathode, segregation of BaCrO₄ and Co₃O₄ on the surface of ME-PBCC is significantly suppressed, which is attributed to its higher configurational entropy. Electrical conductivity relaxation (ECR) and electrochemical impedance spectroscopy (EIS) results indicate that electrochemical stability of the ME-PBCC cathode has been significantly improved. Among the improvements, after Cr deposition for 48 h, the oxygen surface exchange coefficient k_chem of the medium-entropy cathode decreases from 4.4×10^-4 cm·s^-1 to 1.8×10^-4 cm·s^-1, with the reduction of k_chem significantly lower than that of PBCC (which decreases from 7.3×10^-4 cm·s^-1 to 1.2×10^-4 cm·s^-1). Furthermore, the EIS results after treatment in Cr-containing air at 700 ℃ for 48 h show that the polarization resistance (R_p) of ME-PBCC is only 0.07 Ω·cm², which is lower than 0.11 Ω·cm² of PBCC, confirming that the medium-entropy cathode has significantly improved operational stability and Cr resistance. This study demonstrates that ME-PBCC is a promising cathode material for SOFCs.

Key words: solid oxide fuel cell, double perovskite cathode, configuration entropy, cation segregation, chromium tolerance

CLC Number:

TQ174

WANG Zhe, HAO Hongru, WU Zonghui, XU Lingling, LÜ Zhe, WEI Bo. Enhancing Cr-tolerance Ability of Double Perovskite Cathodes through Configuration Entropy Engineering[J]. Journal of Inorganic Materials, 2025, 40(12): 1341-1348.

Figures/Tables 11

Fig. 1 Crystal structures and XRD patterns of PBCC and ME-PBCC (a) Schematic demonstrations of structures and (b) XRD patterns for PBCC and ME-PBCC; (c) Rietveld XRD pattern for ME-PBCC

Fig. 2 SEM images of PBCC and ME-PBCC pellets treated under different conditions (a-c) SEM images of PBCC after (a) polishing and heat treatment in dry Cr-containing air at (b) 700 and (c) 800 ℃ for 12 h; (d-f) SEM images of ME-PBCC after (d) polishing and heat treatment in dry Cr-containing air at (e) 700 and (f) 800 ℃ for 12 h. Inserts in (b, e): corresponding distributions of particle sizes

Fig. 3 (a) SEM image and (b) corresponding EDS elemental analysis of the surface of PBCC sample after treatment in Cr-containing air for 12 h at 800 ℃

Fig. 4 (a, b) SEM-EDS elemental mappings and (c, d) corresponding spectra for the surface of (a, c) PBCC and (b, d) ME-PBCC

Fig. 5 Raman mappings and corresponding spectra from marked points of Co3O4 and CrO42- for (a) PBCC and (b) ME-PBCC pellets after Cr-poisoning at 800 ℃ for 12 h Colorful figures are available on website

Fig. 6 ECR curves, oxygen surface exchange coefficients (kchem) and bulk diffusion coefficients (Dchem) (a, b) ECR curves for (a) PBCC and (b) ME-PBCC before and after Cr deposition at 700 ℃; (c, d) Results for (c) kchem and (d) Dchem

Fig. 7 EIS spectra and corresponding DRT analysis of PBCC and ME-PBCC (a) Variation curves of Rp with time at 700 ℃ in Cr-containing air; (b, c) EIS spectra of (b) PBCC and (c) ME-PBCC; (d, e) DRT curves of (d) PBCC and (e) ME-PBCC

Fig. S1 Rietveld refined XRD pattern of PBCC

Fig. S2 EDS elemental analysis of initial PBCC and ME- PBCC pellets

Table S1 Results of the refined cell parameters of PBCC and ME-PBCC

Sample	Space group	a/Å	b/Å	c/Å	Volume/Å³
PBCC	P4/mmm	3.878	3.878	7.628	114.72
ME-PBCC	P4/mmm	3.877	3.877	7.606	114.33

Fig. S3 SEM images and EDS elemental distribution mappings excluding Pr, Ba, Co, and Cr elements of (a) PBCC and (b) ME-PBCC

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