Performance of Pr2(Ni,Cu)O4+δ electrodes in protonic ceramic electrochemical cells with unseparated and separated gas spaces

Abstract

The Ln 2 NiO 4+δ -based layered phases have attracted much attention as components for high-performance protonic ceramic fuel cells (PCFCs) and electrolysis cells (PCECs) enabling energy conversion with good efficiency and low pollution. The present paper aims at rationally engineering the Cu-doped Pr 2 NiO 4+δ materials and analysing their electrode behaviour for reversible protonic ceramic cells operating in both PCFC and PCEC modes. Complex oxides of Pr 2 Ni 1– x Cu x O 4+δ ( x = 0, 0.1, 0.2 and 0.3) were synthesised using the citrate-nitrate method. The obtained materials were characterised considering their crystalline structures, as well as thermal, thermomechanical and electrotransport properties. A special interest was focused on the quality of an electrode/electrolyte interface governing the electrochemical performance of the cells fabricated. It is shown that a copper doping of x = 0.2 has a positive impact on the thermomechanical compatibility of the Ba(Ce,Zr)O 3 -based electrolytes, providing a better adhesion to these electrolytes at low-temperature sintering and resulting in a decrease of the polarisation resistance of the air electrodes. A reversible protonic ceramic cell demonstrates a power density of ~340 mW cm –2 and a hydrogen output flux of ~3.8 ml cm −2 min −1 at 750 °C. The presented results propose modernised alkaline-earth-element-free and cobalt-free electrodes that can be successfully used in the electrochemical cells based on the-state-of-the-art proton-conducting electrolytes. • Pr 2 Ni 1– x Cu x O 4+ δ phases (where x = 0, 0.1, 0.2 and 0.3) were successfully prepared • Links between composition, defect structure and properties were elucidated • Pr 2 Ni 0.8 Cu 0.2 O 4+ δ (PNC0.2) shows the best thermomechanical characteristics • PNC0.2 exhibits also the improved electrochemical properties • PNC0.2 is a promising oxygen electrode candidate for SOFCs, SOECs or rSOCs.