Even in the well-electrified Sweden, 70% of the energy is consumed as fuel, and most liquid fossil fuels are used in the transport sector. Due to the low solar-to-biomass energy storage efficiency of plants (< 0.5%), local biomass contributes only with less than 2.5% to the transportation fuels in Sweden. The expansion of the H2 refueling station network in Europe, and the release of H2 fuel cell vehicles to market, makes H2 an attractive alternative transportation fuel. Burning of H2 releases only water, and thus H2 is in principle a 'clean' fuel. Presently, the problem is that nearly all H2 is produced from fossil fuels since present electrolyzers are too expensive or unsuitable for intermittent operation. For bringing renewable energy driven electrolyzers to market, new cheap, efficient and stable catalysts are required. In this project, we focus on molecular catalysts for water oxidation made from base metals. The molecular approach has been very successful in converting the first molecular water-splitting catalyst, a Ru-dimer, from a poor catalyst to performing better than the natural system in photosynthesis. For meeting this challenge, we combine our local strong expertise in photosynthesis, coordination chemistry, electrochemistry, EPR, FTIR and X-ray spectroscopies, theory and mechanistic studies to systematically study existing base metal water-splitting catalysts, and for designing catalysts with improved catalytic efficiency and stability. In the project we will simulate electrochemical properties, reaction mechanism, and stability with respect to side reactions. We will also perform simulations to identify intermediates from their spectral fingerprints.