A Reversible Protonic Ceramic Cell with Symmetrically Designed Pr2NiO4+δ-Based Electrodes: Fabrication and Electrochemical Features

Abstract

Reversible protonic ceramic cells (rPCCs) combine two different operation regimes, fuel cell and electrolysis cell modes, which allow reversible chemical-to-electrical energy conversion at reduced temperatures with high efficiency and performance. Here we present novel technological and materials science approaches, enabling a rPCC with symmetrical functional electrodes to be prepared using a single sintering step. The response of the cell fabricated on the basis of P–N–BCZD|BCZD|PBN–BCZD (where BCZD = BaCe0.5Zr0.3Dy0.2O3−δ, PBN = Pr1.9Ba0.1NiO4+δ, P = Pr2O3, N = Ni) is studied at different temperatures and water vapor partial pressures (pH2O) by means of volt-ampere measurements, electrochemical impedance spectroscopy and distribution of relaxation times analyses. The obtained results demonstrate that symmetrical electrodes exhibit classical mixed-ionic/electronic conducting behavior with no hydration capability at 750 °C; therefore, increasing the pH2O values in both reducing and oxidizing atmospheres leads to some deterioration of their electrochemical activity. At the same time, the electrolytic properties of the BCZD membrane are improved, positively affecting the rPCC’s efficiency. The electrolysis cell mode of the rPCC is found to be more appropriate than the fuel cell mode under highly humidified atmospheres, since its improved performance is determined by the ohmic resistance, which decreases with pH2O increasing.

One-Step Fabrication of Protonic Ceramic Fuel Cells Using a Convenient Tape Calendering Method

“…In order to achieve successful results, it was necessary to take several factors into consideration: (a) the electrolyte must be fully densified, while the electrodes should have a sufficient porosity; (b) all the functional materials need to exhibit similar thermomechanical properties; (c) no significant chemical interactions should occur at the anode/electrolyte and electrolyte/cathode interfaces. Taking these limitations into account, BaCe 0.5 Zr 0.3 Dy 0.2 O 3-δ + 0.5 wt% CuO (BCZD) was selected as a proton-conducting electrolyte [28,32], while Pr 1.9 Ba 0.1 NiO 4+δ (PBN) was used to form a cathode [29]. In detail, BCZD is characterised by good protonic conductivity levels, coupled with a high chemical stability in highly moisturised atmospheres.…”

“…A small amount of copper oxide was added as an aid [33,34] to promote BCZD sinterability. PBN was selected due to its good chemical and thermal compatibilities with BCZD, even at 1350 • C [29].…”

“…Therefore, as an alternative approach, we herein propose a tape calendering method as a simple, scalable and efficient means for one-step fabrication of PCFCs. The possibility of one-step fabrication is based on our recent achievements in materials science (the selection of chemically and thermally compatible materials [28,29]) and technological (the rational parameter tuning of the tape calendering method [30,31]) fields.…”

Oxygen transport in Pr nickelates: Elucidation of atomic-scale features

“…Pr 2 NiO 4+δ oxide with a layered Ruddlesden-Popper (R-P) structure is a promising material for SOFC cathodes [1][2][3][4][5][6][7][8], electrodes for electrolysers and reversible cells [9,10] and oxygen separation membranes [11][12][13][14] due to a high oxygen mobility provided by the cooperative mechanism of oxygen migration involving both interstitial oxygen species and apical oxygen of the NiO 6 octahedra, as well as intermediate values of thermal expansion coefficients (TECs) and stability to carbonization [3,5,11,[15][16][17][18][19][20]. Doping is usually applied to diminish Pr 2 NiO 4+δ phase instability in the temperature range of 850-1000°C [21].…”

Manipulating the grain boundary properties of BaCeO3-based ceramic materials through sintering additives introduction

“…Proton-conducting oxide (PCO) materials occupy a special place in the high-temperature electrochemistry due to its unique features consisting in proton transportation in an oxide matrix [1][2][3][4][5]. These features allows PCOs to be utilized as electrolytes for various types of electrochemical devices (EDs) such as solid oxide fuel cells (SOFCs), solid oxide electrolysis cells (SOECs), pumps and sensors [6][7][8][9]. As a result of high realizable conductivity levels of PCOs, the mentioned devices can operate at reduced temperatures (below 600 °C) compared with the conventional systems based on oxygen-ionic electrolytes [10,11].…”