The development of catalysts for the electrochemical activation of small molecules for energy storage or the synthesis of feedstock for the chemical industry is subject of intensive research. The most common reaction in this context is splitting of water into H2 and O2 and the direct reduction of CO2 to green fuels and feedstock for the the chemical industry. Other processes of high interest are the electrochemical activation of C-H bonds or the generation of H2O2 through water oxidation. In this project a fundamental mechanistic understanding for the aforementioned reactions will be developed. In addition, we will also focus on developing tools to predict acid-base properties at surfaces and in non-aqueous solvents. I) Water Splitting: We will study the reaction mechanisms responsible related to O2, H2O2 and H2 production. Currently, the oxygen evolution reaction (OER) still suffers from a significant lack in efficiency and the need to rely on scarce and expensive metals (Ru, Ir, Pt). Furthermore, selectivity in the presence of cl- ions or towards H2O2 production is still poorly understood. Our research will focus on developing a fundamental understanding of the underlying reaction mechanisms using either common catalysts like IrO2 or simple molecular systems as a test materials to establish fundamental reaction mechanisms. In later steps also screenings for more efficient materials may be performed. Furthermore, novel materials such as doped transition metal oxides or novel ligand systems will be studied as a part of this project. II) CO2 reduction: A promising alternative to water splitting is the direct reduction of CO2 to CO, methanol, formaldehyde, methane, etc. This process is appealing, since it offers direct access to feedstock for the chemical industry and liquid fuels. Unfortunately, we still lack active and selectivity catalysts. In this project we will re evaluate the performance of porphyrin and phthalocyanine catalysts and in addition also study bi nuclear molecular catalysts. The latter have rarely been considered in the literature so far and detailed reaction mechanisms are still missing. III) Acid-base chemistry in non-aqueous solvents and at surfaces: Acid-base chemistry is one of the most important reaction classes which affects all areas of chemistry but is also of relevance in e.g. biology and geology. We already possess efficient tools for pKa prediction in water but still lack the tools to accurately predict acidity of surface sites and in non-aqueous solvents. These projects will take advantage of a novel procedure to predict single ion solvation energies which was developed during the prior funding periods. The research will mostly rely on DFT while AIMD and force field based MD simulations are used to predict solvation energies. The solvation energies are combined with gas phase DFT or CCSD(T) computations to predict accurate pKa values. Contrary to most other research groups, we will focus equally on homogeneous and solid-state catalysts. This will enable us to build bridges between these still poorly connected research fields.