In order to overcome the 80% barrier of electricity grids powered by fossil fuels and pave the way for sustainable energy, the use of electrochemical conversion and storage devices using hydrogen as an energy carrier, obtained from renewable sources, is of great interest. In this context, water electrolyzers, fuel cells, and regenerative fuel cells stand out for their high energy conversion efficiency. This project will develop a series of novel hybrid composite materials to study the reactions occurring at the electrodes of these devices: hydrogen evolution (HER) and oxygen evolution (OER) in electrolyzers and regenerative fuel cells; and oxygen reduction (ORR) and hydrogen oxidation (HOR) reactions in both fuel cells. Hybrid materials will be synthesized using carbonaceous materials doped with heteroatoms (S, N, P) and other inorganic compounds such as metal carbides. The effect of ionic liquids on the activity and stability of the resulting composites will be studied (since they can act simply as a binder or as a catalyst) in both basic and acidic media. The catalytic activity of graphene quantum dots will also be investigated. Finally, non-noble metals (Cu, Fe, Ni, Mo) will be introduced as potential catalysts. The aim is to increase electrocatalytic activity while avoiding the use of noble metals, leading to a significant reduction in the cost of catalysts for these devices. The prepared materials will be structurally characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), scanning tunneling microscopy (STM), and Raman spectroscopy (RM). Textural and functional analyses will also be performed using adsorption isotherms of appropriate probe molecules. The chemistry of the different carbonaceous materials will be studied using temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and elemental analysis. Electrochemical reactions will initially be investigated using conventional electrochemical techniques such as linear or cyclic scanning voltammetry and rotating disk electrodes. Finally, spectroelectrochemical studies will be conducted, applying in-situ spectroscopic techniques adapted to the electrochemical systems, specifically Raman spectroscopy, Fourier transform infrared spectroscopy, and mass spectrometry. Disk and ring techniques and scanning electrochemical microscopy will also be applied in order to evaluate and understand the fundamentals and mechanisms in the electrochemical reactions of hybrid nanocomposites, so that an optimized design of these materials can be achieved by studying their structure-activity relationship.