Exsolution and electrochemistry in perovskite solid oxide fuel cell anodes: Role of stoichiometry in Sr(Ti,Fe,Ni)O₃

Journal Article · Thu Sep 05 00:00:00 EDT 2019 · Journal of Power Sources

DOI:https://doi.org/10.1016/j.jpowsour.2019.227077· OSTI ID:1599125

Zhu, Tenglong  ^[1]; Troiani, Horacio ^[2]; Mogni, Liliana V.  ^[2]; Santaya, Mariano ^[2]; Han, Minfang ^[3]; Barnett, Scott A.  ^[4]

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1. Northwestern Univ., Evanston, IL (United States); Nanjing Univ. (China)
2. Comision Nacional de Energia Atomica (CNEA), Rio Negro (Argentina). Centro Atomico Bariloche (CAB)
3. Tsinghua Univ., Beijing (China)
4. Northwestern Univ., Evanston, IL (United States)

The exsolution of metal cations from oxides under reducing fuel conditions ends in the formation of surface metallic nanoparticles, which can reduce Solid Oxide Fuel Cell anode polarization resistance. However, the loss of the B-site cations shifts the stoichiometry of the perovskite oxide. Depending on the amount exsolved and the initial stoichiometry, the exsolution can presumably shift the oxide away from its single-phase perovskite region. Herein, the direct comparison of initially stoichiometric composition Sr(Ti_0.3Fe_0.63Ni_0.07)O_3-δ (STFN0) with initially A-site deficient Sr_0.95(Ti_0.3Fe_0.63Ni_0.07)O_3-δ (STFN5) is conducted and reported. X-ray diffraction along with scanning and transmission electron microscopy analysis of the oxides, which are both reduced at 850 °C in H₂/H₂O/Ar, demonstrates a similar size and density of exsolved Fe–Ni alloy nanoparticles, albeit with slightly different alloy compositions. Whereas the oxide phase in reduced STFN5 shows a well-ordered perovskite structure, the greater B-site deficiency in reduced STFN0 results in a highly disordered and strained structure. The electrochemical performance of STFN0 anodes is inferior to that of STFN5 anodes, and even worse than SrTi_0.3Fe_0.7O_3-δ (Ni-free) anodes. It appears that an initial Sr deficiency is important to avoid a too-high B-site deficiency after exsolution, which distorts the perovskite structure and impairs electrochemical processes.

• Research Organization: Northwestern Univ., Evanston, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; National Natural Science Foundation of China (NSFC); National Key Research and Development Program of China; Keck Foundation; USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; National Science Foundation (NSF)
• Contributing Organization: International Institute for Nanotechnology (IIN)
• Grant/Contract Number: SC0016965; DMR-1121262; NNCI-1542205; 51702163; 2018YFB1502203
• OSTI ID: 1599125
• Alternate ID(s): OSTI ID: 1560700; OSTI ID: 1658924
• Journal Information: Journal of Power Sources, Vol. 439, Issue C; ISSN 0378-7753
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
Solid oxide fuel cell
Sr(Ti
Fe
Ni)O3
Perovskite anode
Exsolution
Stoichiometry
30 DIRECT ENERGY CONVERSION