An Efficient Steam‐Induced Heterostructured Air Electrode for Protonic Ceramic Electrochemical Cells

Abstract

The development of active and durable air electrodes is of great significance to the maturity of reversible protonic ceramic electrochemical cells (R‐PCECs). This article reports the recent findings in the performance enhancement of R‐PCECs using a novel heterostructured air electrode, consisting of a double perovskite PrBaCo1.6Fe0.2Nb0.2O5+δ backbone covered with in situ exsolved nanoparticles of Nb‐deficient PrBaCo1.6Fe0.2Nb0.2−xO5+δ. Such a heterostructured electrode is induced by the benign interaction of the electrode and steam during the cell operation, showing a faster surface exchange process, as confirmed by a mapping of high‐angle annular dark‐field transmission electron microscopy image, and distribution of relaxation time analyses of the electrochemical impedance spectra. The in situ formed Nb‐deficient nanoparticles and Nb‐rich parental perovskite significantly enhance the catalytic activity and durability of the air electrode toward oxygen reduction/evolution reaction on single cells at 650 °C, achieving a peak power density of 1.059 W cm−2 in fuel cell mode, a current density of 2.148 A cm−2 at 1.3 V in electrolysis cell mode, and good durability of a cycling test at ±0.5 A cm−2 for 200 h in dual modes of fuel cell and electrolysis cell.

Enhancing the oxygen reduction reaction activity and durability of a double-perovskite via an A-site tuning

“…The O 1s core-level spectra can be deconvoluted into three overlapping bands (Fig. 2f) [4,29,30]. The peak at around 528.7 eV is assigned to the lattice oxygen (O lat ), and the peak at around 530.8 eV is corresponding to the surface adsorbed oxygen (O ads , including O 2− , O − , and OH − ), relating to the surface defect [31].…”

“…Perovskite materials have received wide attention in many technologies relevant to energy storage and conversion, ranging from catalysts in solid oxide fuel cells (SOFCs) to lightabsorbing layers in solar photovoltaics [1,2]. Rational optimization strategies (such as element doping, introducing defects, and surface modification) of the A-site cation in perovskite oxides are of great significance to enhance the performance and durability [3][4][5][6][7]. Perovskite-based materials have been intensively applied as cathode materials for SOFCs, one of the most promising energy storage and conversion devices because of their high efficiency and environmental friendliness [8][9][10].…”

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

“…Great efforts have been devoted to developing high-performance air electrodes for PCECs. − Some double-perovskite oxides exhibit outstanding performance as air electrodes for protonic ceramic electrochemical cells due to their ability to conduct electrons, oxygen ions, and protons. Representative material systems include PrBaCo 1.6 Fe 0.2 Nb 0.2 O 5+δ (PBCFN), Ba 1– x Gd 0.8 La 0.2+ x Co 2 O 6−δ (BGLC), and PrBa 0.8 Ca 0.2 Co 2 O 5+δ (PBCC) . For instance, Xu et al reported that the PBCFN air electrode achieved 2148 mA cm –2 at a voltage of 1.3 V and 650 °C with 3% H 2 O–air and demonstrated durability for 200 h. Zhou et al fabricated PBCC air electrode and achieved a current density of 1510 mA cm –2 at 1.3 V and 600 °C with 3% H 2 O–air.…”

Insights into Hydration Enthalpies of Mixed Proton–Electron Conductors

“…Protonic ceramic electrochemical cells (PCECs) that can fluently switch their operation modes between power-generating fuel cell (FC) and fuel-producing electrolysis cell (EC) are deemed as one of the most promising technologies for long-term and large-scale energy conversion and storage. − Unfortunately, the practical application of PCECs has been largely hindered by the sluggish kinetics of proton involved oxygen reduction reaction (P-ORR) and proton involved oxygen evolution reaction (P-OER) at the air electrodes, as described in eqs and in Kröger-Vink notation.…”