As a result of recently growing efforts in the area of sustainable energy and resulting increased interest in energy storage and conversion, the fields of catalysis, electrochemistry, and materials research are now experiencing a peak. Involved areas are fuel cell technology, water electrolysis, battery research, and solar cells. A novel method for achieving controlled surface structuring by growing the nanoparticles in-situ under catalytic reaction conditions, directly from the host material itself (by exsolution), which represents a new, easy, highly time- and cost-efficient way of catalyst preparation.
The materials we utilize to perform this task are perovskite-type oxides. They offer the opportunity to design the active catalysts as fuel cells with working and counter electrodes and electric contacts. This enables us to apply voltage to the sample and apply an electric potential to the catalyst surface. This potential can be utilized to control and fine tune the exsolution process and thus the nature of the formed nanoparticles, and also to enhance the catalytic reactivity of the surface. This allows control over the surface reactivity and catalyst structure in real time by an external signal (here the applied voltage) and offers the possibility to design catalysts exactly for their respective catalytic application.
To test the capabilities of our novel perovskite catalyst, we use them in catalytic reactions that are highly relevant for chemical energy conversion (see reactions A - D). Chemical energy conversion is needed to be able to store excess renewable energy from e.g. wind or solar power. The reason is that one of the major drawbacks of renewable energy is its strong dependence on regional or seasonal aspects. For example, wind power plants deliver excess energy during storm seasons that is currently not utilized. With chemical energy conversion this excess energy can be stored and then released again when needed.
The catalytic reactions of interest are reversible (that means depending on the direction of the reaction different processes occur) – from the viewpoint of sustainable energy production, storage, and conversion the most impactful reactions are:
A) water splitting 2 H2O ⇌ 2 H2 + O2 hydrogen oxidation
B) water gas shift CO + H2O ⇌ CO2 + H2 reverse water gas shift
C) CO oxidation 2 CO + O2 ⇌ 2 CO2 CO2 electrolysis
D) methanol reforming CH3OH + H2O ⇌ 3 H2 + CO2 methanol synthesis
Due to the reversibility of the reactions (for energy storage and later release) our novel perovskites are tested for both reaction directions.
