High temperature in operando and in situ spectroscopy on electrified surfaces and interfaces

Electrochemical cells, such as fuel cells, electrolyzers and batteries are considered as important technologies for storing electricity from renewable sources and also provide an efficient way of converting chemical energy into electricity. The processes in the electrodes are strongly influenced by the surface electrocatalytic properties, especially if instead of (or in addition to) hydrogen more complex reactants such hydrocarbons in form of alcohols, methane or higher hydro carbons are used as reactants. High temperature, solid state electrochemical cells based on an oxide ion conducting electrolyte are particularly attractive since hydrocarbon fuels in principle can be directly converted into electricity and vice versa with high efficiency. However, several side effects such as coking and poisoning with impurities e.g. sulfur on the fuel electrode, but also indication of changes in surface chemistry of oxide electrodes without contaminants have demanded a better insight into the electrode surface reactions and chemistries. Spectroscopic techniques can be applied to these cells but are still experimentally challenging due to the high temperature operation conditions. DTU Energy has in the recent years invested in specific equipment that allows investigating the electronic, electrical and chemical structure of surfaces under polarization at high temperatures and controlled atmospheres, allowing investigation of electrochemical cells and interfaces under close to operation conditions. The contribution will present selected examples of Raman spectroscopy, Kelvin probe and scanning probe microscopy applied to solid oxide electrochemical cells.