Pr₂BaNiMnO_7−δ double-layered Ruddlesden–Popper perovskite oxides as efficient cathode electrocatalysts for low temperature proton conducting solid oxide fuel cells

Abstract

The performance of low-temperature solid-oxide fuel cells (LT-SOFCs) is heavily dependent on the electrocatalytic activity of the cathode toward the oxygen reduction reaction (ORR).

Materials development and prospective for protonic ceramic fuel cells

“…The lower activation energy for the migration of protons through the electrolyte and the formation of water at the cathode is advantageous. 75,76 They give PCFCs an edge over the oxygen ion-conducting SOFC because there will be no problem of fuel dilution at the anode since the water formation will only occur at the cathode. Thus, the unreacted hydrogen fuel can be directly recycled for reuse.…”

“…89,118,164 The materials that are reported to be most suitable for achieving excellent triple conducting singlephase cathodes are either ABO 3Àδ perovskites, A 0 AB 2 O 5þδ double perovskites, and A nþ1 B n O 3nþ1 Ruddlesden-Popper with their A and B sites doped with elements such as Ba, Sr, Zr, Cu, Mn, Co, and Ni. 26,75,[165][166][167][168][169] It is best to consider materials with cubic structures and large lattice volumes because they enhance hydration and proton conduction. It is also essential when selecting dopants to consider transition metals with multiple oxidation states because that will significantly enhance redox capability and good electronic conductivity.…”

“…The electrolyte of PCFC conducts protons while that of O-SOFC conducts oxygen ions during operation.O-SOFCs are characterized by the migration of oxygen ions from the cathode side to the anode side through the electrolyte membrane when the air supplied to the cathode is reduced after reacting with the electrons received from the anode via the externally connected circuit.In contrast to the traditional oxygen ion-conducting SOFC where oxygen ions migrate from the cathode to the anode, the protonic ceramic fuel cells (PCFCs) are SOFCs in which the migration species are predominantly protons, which migrate from the anode to the cathode at relatively lower activation energy with the formation of water at the cathode side as illustrated in Figure1. The lower activation energy for the migration of protons through the electrolyte and the formation of water at the cathode is advantageous 75,76. They give PCFCs an edge over the oxygen ion-conducting SOFC because there will be no problem of fuel dilution at the anode since the water formation will only occur at the cathode.…”

High-performance proton-conducting solid oxide fuel cells using the first-generation Sr-doped LaMnO3 cathode tailored with Zn ions

“…However, the encouraging performance of the LSMZ cell tackles this problem. The cell performance is even higher than or comparable to some of the recently reported high-performance H-SOFCs based on novel cathodes [5,36,[40][41][42][43][44][45][46][47]. The result indicates that the Zn-doping strategy effectively brings LSM back to the intermediate-temperature range with high performance, although LSM is the first-generation cathode that has been regarded only to perform well at high temperatures (above 800°C).…”

Perspectives on Cathodes for Protonic Ceramic Fuel Cells

“…The substitution of Co with Cu lowered electrical conductivity, but a better thermal compatibility with the electrolyte was achieved. Wang et al [108] reported a Pr 2 BaNiMnO 7−δ cathode that showed excellent compatibility with BCZYYb7111 electrolyte and generated a remarkable MPD of 1.07 W•cm −2 at 700 • C with almost negligible degradation after 100 h. The role of the effect of A-site cation ordering on the cathode performance and chemical stability in double perovskites is investigated for A-site cation-ordered LaBaCo2O5+δ and -disordered La0.5Ba0.5CoO3−δ by Bernuy-López et al [104], observing that A-site cation ordering leads to a higher oxygen-vacancy concentration, which explains the better electrochemical performance of LaBaCo2O5+δ compared to the disordered phase. An A-sitedeficient, layered perovskite, (PrBa0.8Ca0.2)0.95Co2O6−δ, was developed as an oxygen electrode for a reversible protonic ceramic cell where current density reached −0.72 A•cm −2 at 1.3 V, and a peak power density of 0.540 W•cm −2 was obtained at 600 °C in electrolysis and fuel-cell mode, respectively, which were much higher values than the A-site stoichiometric analogue [105].…”