Electrochemical H₂O splitting

The efficiency of electrochemical water splitting for a sustainable production of clean fuels is limited by the large overpotential of the anodic oxygen evolution (OER) reaction. The OER is a complex multi-step reaction with single electron transfer at each step. Understanding the underlying mechanisms of OER for different anodic materials is therefore of great importance for developing efficient catalytic materials. A promising class currently under investigation are metal oxides with perovskite structure.

In-situ environmental transmission electron microscopy (ETEM) in combination with image simulations gives insides into the active state of water splitting. The perovskite La1-xSrxMnO3, e.g., shows fast manganese adatom mobility at the interface to H2O related to partial solvation of surface manganese atoms in liquid H2O surface layer. Such a dynamic interface has a big impact on understanding highly efficient pathways for the OER.

Atomic-scale studies require electron-transparent and almost cristallographically perfect surfaces, i.e., preparation must be done with great care. A focused ion beam (FIB) system is used in combination with a polymer protective layer to minimize preparation-related damage to the sample. Post-treatments in the ETEM like recrystallization in the presence of oxygen can be used to further improve the crystallographic quality.