Quantitative analysis of the platinum surface decoration on lanthanum strontium iron oxide thin films via online-LASIL-ICP-MS

Solid oxide fuel cells (SOFCs) are one of the key technologies on the way to environmentally friendly power generation. Current research activities aim to reduce their operational temperature to intermediate temperatures (400-600 degrees C) to make their application more feasible. In a recent approach, lanthanum strontium iron oxide (LSF) thin film electrodes, a mixed ionic electronic conducting (MIEC) material, was decorated with tiny amounts of platinum nanoparticles, which led to a significant improvement of the oxygen reduction kinetics. To understand this material combination a precise characterization is of major interest, especially the exact amount of platinum on the surface. As the studied model-type thin film electrode requires a platinum current collector buried beneath the LSF to improve in-plane electron conductivity, a method providing quantitative information as well as sufficient depth resolution is needed. In this work, we further improved the recently presented approach of online laser ablation of solids in liquids (LASIL), which enabled in combination with ICP-MS detection a spatially resolved analysis of the sample composition. Careful optimization of laser parameters and carrier solution led to a depth resolution of 30 nm, which allowed a clear separation of the Pt-signals from the surface decoration and the underlying current collector. The amount of platinum on the surface was determined using calibration with a matrix matched standard and validated by another method. Finally, the imaging capabilities of the proposed online-LASIL approach have been employed to assess the homogeneity of the Pt-decoration, indicating significant variations within the investigated area. Thus, further improvements in the electrochemical properties of the investigated LSF electrodes could be anticipated by fabrication of MIECs with a more homogeneous platinum decoration.

Automated summary

Solid oxide fuel cells (SOFCs) are a key technology for environmentally friendly power generation, with current research focusing on lowering their operating temperature for better application. By using online laser ablation of solids in liquids (LASIL) in combination with ICP-MS detection, the amount of platinum on the surface of lanthanum strontium iron oxide (LSF) thin film electrodes was accurately characterized, revealing the significant impact of platinum decoration homogeneity on the electrochemical properties of the electrodes.