Effect of Backbone Selection on the Enhanced Electrocatalytic Activity of Pr2Ni0.6Cu0.4O4 Infiltrated Oxygen Electrodes
Authors: Khoshkalam Mohamad , Hendriksen Peter Vang 
Published: February 2024

Infiltration is proved to be a highly efficient technique for increasing the electrocatalytic activity of oxygen electrodes in solid oxide fuel/electrolysis cells (SOFC/SOEC). One of the main advantages of this technique is the flexibility of choosing various backbone/surface-decoration combinations. The selection of correct backbone/surface-decoration combination is one of the challenges in developing the infiltrated oxygen electrodes. It is suggested that via choosing the correct combination, one can synergistically improve the electrochemical performance. Pr-based-Ruddlesden-Popper-nickelates such as Pr2Ni0.6Cu0.4O4 (PNCO) was recently demonstrated to be an efficient Cobalt-free and Alkaline earth-free electrocatalyst for oxygen reduction/evolution reaction (ORR/OER) when used as a surface decoration phases. Here, in this study, PNCO as a model electrocatalyst is infiltrated into various porous backbones of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), Ce0.9Gd0.1O2 (CGO), La0.6Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 (LSCF/CGO) and LaNi0.6Fe0.4O3/Ce0.9Gd0.1O2 (LNF/CGO) with various levels of ionic and electronic conductivity, and effect of infiltration loading on polarization and series resistance of symmetrical cells was investigated. The results showed that to achieve high performances via surface decoration of ionic conductor backbones, such as CGO, usually very high infiltration loadings as high as 15-30 wt% is required. The reason behind such high loadings is the fact that the surface decoration phases are the only sources of electronic conduction, and therefore high infiltration loadings are necessary to attain sufficient percolation of the electronic conducting phase. However, if the surface decoration phase does not possess high electronic conduction, which is the case for oxides such as PNCO, then additional paths for electronic conduction must be created in the electrode network to prevent current constriction effects. This additional path can be generated via replacing some fraction of the ionic conductor phase in the backbone with the electronic conductor phases such as LNF and LSCF. The other common strategy for developing efficient infiltrated oxygen electrode is the surface decoration of a mixed-ionic-electronic-conductor MIEC backbone (such as LSCF) with another MIEC phase (PNCO). The best performances in these types of infiltrated electrodes are achieved with significantly less infiltration loading compared to infiltrated ionic conductor backbones with values as low as 10 wt%. In this study, marked performance improvements were achieved with 10 wt% infiltration loading of PNCO, including a reduction by a factor of 2 of the polarization resistance at 650 °C for both LSCF (0.22 Ω.cm2 to 0.1 Ω.cm2) and the LSCF/CGO (0.15 Ω.cm2 to 0.06 Ω.cm2) state of the art electrodes. In CGO as well as LNF/CGO composite backbone, infiltration with 30 wt% of PNCO led to enhanced electrode performance improvement, reaching 0.24 Ω.cm2 and 0.1 Ω.cm2 at 650 °C, faster than the state-of-the-art LSCF-CGO (0.15 Ω.cm2) at same temperature, which shows the potential of these highly efficient cobalt-free and alkaline earth-free oxygen electrodes for (SOFC/SOEC) application.

Figure 1