Summary: The decarbonisation of industry has a huge role to play in addressing the climate crisis by drastically reducing greenhouse gas emissions. The urgently needed transition away from fossil fuels will be ultimately based on the efficient production of hydrogen with renewable energy (i.e. green hydrogen). Industrial scale green hydrogen production will primarily come from electrochemical water splitting (i.e. 2H₂O → 2H₂ + O₂) using electrolysers and suitable water sources However, current electrolysers, have high energy costs and rely on expensive scarce materials. HYDROCAT will develop a new class of hybrid organic-inorganic electrocatalysts based on self-assembled monolayers (SAMs) of electroactive organic molecules. These new catalysts will be based on earth abundant (and therefore less costly) materials that promise to split water using less energy than standard approaches. Our approach combines the complementary international expertise and experience of three Catalan institutions (UB: modelling/design of catalysts under working conditions, ICMAB: SAMs of electroactive molecules, ICN2: experimental electrocatalysis) to design, synthesise and test a new SAM-based electrocatalyst concept.