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

Abstract

Great efforts have been devoted to developing high-performance air electrodes for proton-conducting electrolysis cells (PCECs). However, the stability of existing air electrodes still cannot meet the requirement for practical applications, and the degradation mechanisms require further investigation. Herein, taking porous PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF)−BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3−δ (BZCYYb) composite air electrode as the model system, we systematically investigate the impact of steam concentration on the activity and stability of the electrode. The electrode exhibits reduced electrochemical impedance and improved Faradaic efficiency under high steam concentrations. Nevertheless, the hydrogen production performance of the cell degrades rapidly when operating under high steam concentrations (>30%). Such degradation of the cell is mainly attributed to the agglomeration and cation (especially Sr and Ba) segregation of PBSCF, and the decreased oxygen vacancies in BZCYYb caused highly concentrated steams. Our results clarify the critical role of steam on the activity and stability of the air electrode for PCECs. The findings can help guide the development of robust and active catalysts for other high-temperature electrochemical devices.

Energetics of formation and stability in high pressure steam of barium lanthanide cobaltite double perovskites

“…However, a background increase was observed in the PXRD patterns after water vapor treatment, indicating the formation of amorphous hydroxides, which is more obvious after 10.5 bar of pH 2 O for 100 h. This agrees with the recent Pan et al study on PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+ δ (PBSCF)–BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3− δ (BZCYYb) composite positrodes in which they report that high steam concentrations promoted the segregation of Ba and Sr to the surface to form a Sr-OH or Ba-OH phase. 34 The simulation studies show that in the case of perovskites, the surface segregation can be enhanced also by the structural strain. 35 This can suggest that the compositional complexity of BLGC concerning BLnC can play a role in their stability in steam.…”

“…For both samples, the main crystalline products of decomposition at high steam pressures are Gd(OH) 3 and BaCO 3 as well as Co compounds (Co 3 O 4 and Co(OH) 2 ). Though, the existing BaCO 3 is the product of decomposition 34 The simulation studies show that in the case of perovskites, the surface segregation can be enhanced also by the structural strain. 35 This can suggest that the compositional complexity of BLGC concerning BLnC can play a role in their stability in steam.…”

Surface regulating and hetero-interface engineering of an LSCF cathode by CVD for solid oxide fuel cells: integration of improved electrochemical performance and Cr-tolerance

“…The two doublets can be fitted and assigned to the lattice Sr (Sr lat ), which is the Sr in the lattice of LSCF perovskite and the surface Sr (Sr sur ) that is the Sr on the surface of LSCF. 56 The Sr sur /Sr lat proportion can be used to denote the degree of Sr segregation on the surface, and the results are shown in Fig. 7d.…”

Water Electrolysis toward Elevated Temperature: Advances, Challenges and Frontiers

“…For a PCEC with the BZCYYb electrolyte displaying great stability for 600 h under moderate humidity of 20% H 2 O at 600 °C, a voltage degradation rate of 30 mV·kh –1 was exhibited and the corresponding EIS analysis indicated that the cell degradation primarily resulted from electrode performance, while no obvious change in ohmic resistance was observed for the BZCYYb electrolyte . However, a sharp increase of ohmic resistance from 0.458 Ω·cm 2 to 0.624 Ω·cm 2 was observed after merely a 90-h operation under 50% H 2 O, illustrating the severe degradation of BZCYYb electrolyte in the highly humidified environment …”

“…387 However, a sharp increase of ohmic resistance from 0.458 Ω•cm 2 to 0.624 Ω•cm 2 was observed after merely a 90-h operation under 50% H 2 O, illustrating the severe degradation of BZCYYb electrolyte in the highly humidified environment. 391 Given that the decomposition of BaCe 1−x Zr x O 3 -based materials doped with other elements was still detected when sufficient concentrations of H 2 O and CO 2 were present in the surrounding environments, 392 optimizing the electrolyte structure into a bilayer configuration composed of a protective layer on the anode side to prevent destruction derived from steam and a conductive layer on the cathode side has been proposed as a solution. Typically, the protective layer should be as thin as possible for minimized ohmic resistance and have a dense structure for complete isolation from steam, which is normally fabricated through atomic layer deposition (ALD) and PLD.…”