Study of Pr and Pr and Co doped La2NiO4+ as cathodes for La5.5WO11.25− based protonic conducting fuel cells

Abstract

The mixed ionic-electronic conductor La 2 NiO 4+δ was investigated as potential cathode material for protonic conducting solid oxide fuel cells (PC-SOFCs) based on La 5.5 WO 11.25-δ electrolyte. Firstly the chemical compatibility between cathode and electrolyte phases (La 2 NiO 4+δ and La 5.5 WO 11.25-δ respectively) was studied. Then, the electrochemical properties of this cathode were improved by partially substituting La and/or Ni, specifically La 1.5 Pr 0.5 NiO 4+δ and La 1.5 Pr 0.5 Ni 0.8 Co 0.2 O 4+δ were considered. These two doped materials showed improved electrical conductivity and reduced polarization resistance, when tested as cathode in symmetrical cells. In a second step, the microstructure of La 1.5 Pr 0.5 Ni 0.8 Co 0.2 O 4+δ was optimized by varying the firing temperature of the cathode. The performance of these mixed conductors is limited by medium frequencies associated processes while they show lower polarization resistances (Rp) than conventional composites based on La 5.5 WO 11.25-δ and pure electronic conductors. La 1.5 Pr 0.5 Ni 0.8 Co 0.2 O 4+δ cathode sintered at 1050 ºC exhibits the best electrochemical performance on a La 5.5 WO 11.25-δ-based PC-SOFC, achieving Rp=0.62 •cm 2 at 750 ºC in wet air.

Novel La2-x Cu x NiO4±δ /La4Ni3O10-δ composite materials for intermediate temperature solid oxide fuel cells, IT-SOFC

“…2. The doping of lanthanum sites by copper leads to the formation of pure phases with a K 2 NiF 4 structure, in agreement with several studies [8][9][10][25][26][27][28]. It is likely that cupric ions replace lanthanum sites and create additional sites displacement, which improves the electrical conductivity.…”

STRUCTURE, ELECTRICAL PROPERTIES, AND APPLICATION POSIBILITY AS SOLID OXIDE FUEL CELLS CATHODE MATERIALS OF (La2NiO4±δ)1-x(BaTiO3)x(x=0.0-0.5) COMPOSITES

“…Single phase perovskite La 2 NiO 4 (LNO) and other most Ruddlesden-Popper series La n+1 Ni n O 3n+1 (n = 2 and 3) have good oxide-ion conductivity, and are suitable cathode materials for intermediate temperature (650 -800 0 C) SOFC [2]. Authors of [3] found the optimum content for the composite SOFC cathode, which consists of 70 % La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) and 30 % volume percent of LNO. Single cell with this cathode gives an acceptable power density 479 mWcm -2 at 800 0 C. Doped LNO is also promising cathode materials for SOFC [4].…”

The Influence of the Substituting Element (M = Ca, Sr, Ba) in La1.7M0.3NiO4+δ on the Electrochemical Performance of the Composite Electrodes

“…Over the past 10 years the layered nickelate La 2 NiO 4+δ (LNO) with the coefficient of thermal expansion (CTE) α equal to 12.9-13.5 × 10 −6 K −1 , high value of the oxygen surface heteroexchange constant k (2.5 × 10 −6 cm s −1 at 800 °C) and oxygen diffusion coefficient D (1.7 × 10 −7 cm 2 s −1 at 800 °C) [10] has been the subject of intensive studies including its application in an SOFC with proton conducting electrolytes [11][12][13][14]. As far as La 2 NiO 4+δ is a p-type conductor in the temperature range 400-900 °C, appropriate acceptor doping in A-site could improve its electronic conductivity by generating extra electron holes for charge compensation.…”