Electrochemical performance of strontium-doped neodymium nickelate mixed ionic–electronic conductor for intermediate temperature solid oxide fuel cells

Abstract

The Nd 2− x Sr x NiO 4+δ (x00.1-0.5) solid solutions prepared by combustion synthesis are of submicron/superfine crystallite size. The crystal structure estimated by Rietveld analysis reveals increase in space in the rock salt layer on partial replacement of Nd 3+ by Sr 2+ . The transition from negative temperature coefficient to positive temperature coefficient of conductivity is observed at 913 K. The maximum dc conductivity (σ01.3±0.02 Scm −1 at 973 K) is obtained for x00.2 in Nd 2− x Sr x NiO 4+δ . The low dc conductivity compared with reported (≈100 Scm −1 ) is due to high porosity (low relative density) resulting from agglomeration of submicron crystallites. The variation in the conductivity with Sr content in Nd 2−x Sr x NiO 4+δ is understood on the basis of defect chemistry. The electrochemical properties of the cathode materials are studied using electrochemical impedance spectroscopy at various temperatures and oxygen partial pressures. Nd 1.8 Sr 0.2 NiO 4+δ cathode exhibits lowest-area-specific resistance 00.52 ± 0.015 Ohm cm 2 at 973 K. At low P O 2 (<1,000 Pa), oxygen ion transfer from Nd 1.8 Sr 0.2 NiO 4+δ cathode to gadolinium-doped ceria electrolyte is the rate-limiting step, whereas, charge-transfer reaction on the cathode becomes more important at high oxygen partial pressures and temperature (973 K).

Oxygen electrode characteristics of Pr2NiO4+δ-infiltrated porous (La0.9Sr0.1)(Ga0.8Mg0.2)O3–δ

“…La n + 1 Ni n O 3n + 1 has been prepared in the n = 1, 2, and 3 phases [15,16], and even in combination as a functionally graded cathode that combines the high surface exchange of the n = 1 phase with the superior electronic conductivity of the n = 3 phase [17], representing the current best-in-class cathode for La n + 1 Ni n O 3n + 1 with a polarization resistance of 1.06 Ω • cm 2 at 650°C. Nd n + 1 Ni n O 3n + 1 has proven to be reactive with some common electrolytes and has moderate oxygen transport coefficients compared with other rare earth nickelates [18][19][20][21][22].…”

Design and processing parameters of La2NiO4+δ-based cathode for anode-supported planar solid oxide fuel cells (SOFCs)

“…Although a number of studies have been reported to clarify the mechanism of oxygen reduction reaction on RuddlesdenePopper type Ln 2 NiO 4þd (Ln ¼ La, Pr, Nd) cathodes [49,55,75e80], the interpretation of the impedance response is not straightforward and still non-conclusive. Based on the literature, the impedance arcs of Ln 2 NiO 4þd (Ln ¼ La, Pr, Nd) cathodes could be ascribed to a number of elementary reaction processes including ion transfer at the cathode-electrolyte interface [55,79], surface exchange [80], oxygen atomic diffusion [49], charge transfer reaction [77,79], oxygen adsorption/dissociation [78] and gas-phase diffusion [78]. We have performed a systematic analysis on the impedance spectra of the LNOeGDC composite cathode; based on temperature-and pO 2 -dependencies of the individual arcs, the rate limiting processes were identified as the cathode-electrolyte interfacial process and the surface exchange for high-frequency impedance and gas-phase diffusion for low-frequency impedance.…”

Nd 1.8 Sr 0.2 NiO 4−δ :Ce 0.9 Gd 0.1 O 2−δ composite cathode for intermediate temperature solid oxide fuel cells

“…Remarkable improved electrochemical performance due to the partial substitution of Sr in Nd 0.8 Sr 1.2 CoO 4Àd has been demonstrated [20]. Lowest electrode polarization resistance (R p ¼ 0.52 ± 0.015 U cm 2 at 700 C) has been reported for Nd 2Àx Sr x NiO 4Àd when x ¼ 0.2 [21].…”

“…Further, CeO 2 is abundant in the Earth's crust. It has thermo-chemical stability against Nd 1.8 Sr 0.2 NiO 4Àd [21].…”