Optimization of the Lanthanum Tungstate/Pr₂NiO₄ Half Cell for Application in Proton Conducting Solid Oxide Fuel Cells

Abstract

La6WO12, recently reformulated La28–xW4+xO54+3x/2 exhibits a good level of protonic conductivity and chemical stability toward acidic gases. It is therefore a potential material for use as electrolyte in proton conducting solid oxide fuel cells (PC‐SOFC). Pr2NiO4 is a cathode material tested for SOFC in which proton conductivity has been demonstrated recently. In this study, compatibility between lanthanum tungstate and praseodymium nickelate has been investigated by powder X‐ray diffraction (XRD). Microstructure of symmetrical cells based on the lanthanum tungstate and Pr2NiO4 has been analyzed by scanning electron microscopy (SEM) and performance of the cathode has been evaluated by electrochemical impedance spectroscopy (EIS) through the value of the area specific resistance (ASR). To optimize the ASR value, different parameters were modified such as the Pr2NiO4 calcination temperature, the firing temperature of the symmetrical cells, the thickness of the Pr2NiO4 layer, and the composition of the composite cathode. An ASR value of 0.46 Ω cm2 at 700 °C has been obtained showing that lanthanum tungstate electrolyte associated with Pr2NiO4 cathode is a promising half cell for application in PC‐SOFC.

Effects of the La/W ratio and doping on the structure, defect structure, stability and functional properties of proton-conducting lanthanum tungstate La28−xW4+xO54+δ. A review

“…46,47 Optimized 50% Pr 2 NiO 4 -50% LWO composites show ASR values of only 0.5 U cm 2 at 700 C, as such being a promising cathode candidate for use in PC-SOFCs. 48 Focus onwards will be on the regime where LWO is a mixed proton-electron conductor. There is an increasing number of reports on the hydrogen ux in membranes of LWO-based materials, and the potential as a hydrogen permeable membrane has thus been demonstrated.…”

Advances in Cathode Materials for Solid Oxide Fuel Cells: Complex Oxides without Alkaline Earth Metal Elements

“…Since the phase structure of Pr 2 NiO 4 at 750 °C was actually not stable, [ 299,300 ] [ 301 ] In addition to the application as a cathode for SOFCs based on oxygen ion conductors, Pr 2 NiO 4 was even more extensively applied as a cathode for SOFCs based on protonic conductors. [ 281,[302][303][304][305][306] Among the LnNi 2 O 4 (Ln = La, Pr, Nd) series, Pr 2 NiO 4 also showed the highest activity for ORR on proton conducting electrolytes. [ 303 ] Moreover, the polarization resistance, specifi cally at low frequency region, of Pr 2 NiO 4 cathode reduced by introducing water into air.…”

Crystal structure of Mo-substituted lanthanum tungstate La5.4W1−y Mo y O12−δ (0 ≤ y ≤ 0.2) studied by X-ray and neutron diffraction

“…Even though various substitutions on A and B sites in BCO and BZO are being developed (Kjølseth et al, 2010;Dahl et al, 2011;Ricote et al, 2011;Magrasó et al, 2012), as well as ceramic composites (Rebollo et al, 2015;Ivanova et al, 2016), another class of materials has aroused interest for its high protonic conductivity and its stability in harsh atmospheres, namely rare-earth-based tungsten oxides (LnWO, where Ln is a rare earth element). Such materials with Ln = La or Nd could be used as electrolytes in fuel cells because of their almost pure protonic conductivity at low and intermediate temperatures (Haugsrud, 2007;Magrasó, 2013;Quarez et al, 2013). Poor electronic conductivity is a drawback of these materials for applications as hydrogen-permeating membranes.…”