Proton-conducting oxides stand as highly promising materials poised to play an important role in the future of renewable energy technologies. They are applied as as electrolyte and electrode materials in solid oxide fuel or electrolysis cells (SOFCs/SOECs), and as mixed proton- and electron-conducting ceramic membranes for hydrogen purification. For these applications and their optimization, knowledge of the proton concentration in the oxides is key. Notably, some common techniques for analyzing the proton uptake in oxides often rely on indirect methods, such as thermogravimetry or conductivity measurements. Directly measuring protons/hydrogen in oxide ceramics poses a challenge. Among the commonly known analytical methods only a few offer this capability: e.g. neutron diffraction, secondary ion mass spectrometry (SIMS) and infrared (IR) spectroscopy. While neutron diffraction is only possible in corresponding large-scale research facilities, SIMS necessitates the use of an expensive, complex device to work with that is generally not accessible in routine laboratories. Moreover, it operates under high-vacuum conditions, varying widely from operating conditions that can also lead to a falsification of the materials’ proton content. IR spectroscopy, although being a very common method, cannot be used on all materials – e.g. dark electrode materials are particularly tricky to measure.

An analytical method that can circumvent many of these limitations is laser-induced breakdown spectroscopy (LIBS). In LIBS, a high-energy pulsed laser is focused onto the sample surface, inducing local ablation of a minute sample volume. This process generates a high-temperature plasma, emitting characteristic elemental radiation that can be captured and analyzed using a spectrometer. LIBS uniquely enables the observation of every element in the periodic table. It offers spatially resolved measurements with a precision below 100 μm, and depth profiles can be routinely obtained with 1 μm depth resolution. A distinctive advantage lies in the versatility of the laser ablation process, which can be conducted under a wide range of atmospheres. Furthermore, LIBS does not necessitate sample conductivity. This makes LIBS a valuable tool for elemental analysis in general and for quantification of hydrogen/proton concentration in oxides in particular. Especially, when traditional methods face challenges related to cost, accessibility, and compatibility with specific operating conditions, LIBS is an attractive alternative analytical tool.

Here, we introduce a tailored multifunctional sample cell designed for in-situ LIBS measurements on hydrogen/proton containing materials. The cell is capable of achieving temperatures up to 1000 °C and offers the option to vary the atmospheric conditions. Notably, the design incorporates the ability to electrically contact the sample within the cell using up to eight electrodes. This innovative setup facilitates a broad spectrum of electrochemical experiments, including impedance spectroscopy, current-voltage measurements on model-type cells, and Van der Pauw measurements. Simultaneously, it allows for the LIBS-based quantification of the concentrations of protons, oxygen, and various cations in the system. This multitude of possibilities that come together in our new measuring cell opens new avenues for novel experimental approaches. These include combining electrochemical polarization of proton conducting solid oxide cells with elemental characterization and performing diffusion measurements in situ, which provide valuable insights into the behavior of the studied materials under near-operational conditions.