Plasma-based H2 synthesis from hydrocarbons could be a complementary approach to water electrolysis, because it also uses renewable electricity and has no CO2 emission, and in addition, it can valorize CH4 and plastic waste, generate high value C-materials as side-product, and is thermodynamically more favourable. However, before exploiting this application, it is crucial to gain a better fundamental understanding of the plasma processes. This is exactly addressed in our project. We will perform green H2 synthesis experiments from various hydrocarbons and in several plasma types, in gas-phase and in contact with liquids, and develop a multi diagnostics platform for time- and spatially-resolved characterization, as well as novel multi-dimensional, multi scale models, to study the underlying mechanisms in all plasma systems. We will start with simple molecules, i.e., CH4 (gas-phase) and (m)ethanol (liquid-phase), and subsequently develop our methodologies to study H2 synthesis from alkenes (C3-C5 and higher) and styrene, as model systems for (both gas-phase and liquid-phase) pyrolysis products of plastic waste. Besides determining the H2 yield and energy consumption for all systems, and the detailed plasma diagnostics and modelling, we will also characterize the synthesized C, and target the latter as extra value-added product. The project outcomes will lay the basis for green H2 synthesis by plasma technology and will open up a new area in the field of plastic waste recycling