Microstructural refinement of Ni/Ce0.8Gd0.2O2-delta anodes for low-temperature solid oxide fuel cell by wet infiltration loading of PdCl2

Abstract

Microstructural refinement of Ni/Gd0.2Ce0.8O2-delta (Ni/GDC20) anode by wet-infiltration of PdCl2 precursor was studied to further improve the anodic performance of low temperature solid oxide fuel cell (LT-SOFC). The effect of <1 wt% of Pd loadings on polarization resistance of Ni/GDC cermet anodes for H-2 oxidation reaction was examined using symmetric Ni-GDC20IGDC20IPt electrolyte-supported cells at 400-600 degrees C. Nanostructure evolution before and after H-2 reduction at 600 degrees C and also after anodic performance test revealed effectiveness of PdO loading content on the nanoparticles architecture, with Pdaas the sole Pd-phase after calcination at 600 degrees C with no residual chloride. In the process of H-2 reduction in high loading of PdO (0.26 mg/cm(2)), a nano-grained network of metallic palladium (Pd-0) containing nanopores structure, which resulted from 40% volume deoxidizing shrinkage of PdO, was developed on the anode surface. But, in the case of small loading, PdHx phase indicating of H affinity of palladium and minute amounts of PdO on NiO were detected. The significant decrease of anodic polarization resistance, e.g. similar to 100 times at 500 degrees C, on highly Pd-infiltrated anode was accompanied with <= 40 nm agglomerates in Pd-nanonetwork and 45% oxidizing of Pd to PdO in H-2 environment. Detailed anodic impedance analysis and activation energy (E-a) evaluation can be denoted to a balance between the E-a of reaction-limiting step of charge transfer and the E-a of the facilitating step of diffusion/adsorption/dissociation of the arrived O2- species to triple phase boundaries (TPBs). Our findings verified that oxygen spillovering on the Pd-0/PdO-pair nanocoating caused by the shift of the TPBs to the nanocoating-pair for H-2 oxidation reaction in LT-SOFC. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.