Our society’s development depends on the way we use, store, and transform the energy. Currently, we have multiple sources of clean energy to cover the demand of a growing population. However, a big gap remains in the technology to efficiently store the energy that is not being consumed. The purpose of this thesis is to explore carbon-based composite materials to promote the development of new systems for the efficient conversion, use, and storage of energy:​ first, at small-scale storage (batteries) and second, at large-scale storage (power to gas). In both cases, different carbon allotropes and functionalization methods were considered.

The first half of the thesis describes materials and methods to improve the air cathode in Zn-air batteries. These batteries are considered promising energy storage devices because of the numerous advantages such as high energy density, low-cost and abundance of Zn, environmental friendliness, and safety. The first study is focused on developing a double layer membrane fabricated with thermoplastic polyurethane, carbon nanotubes, and activated carbon membrane to improve the oxygen diffusivity and to prevent electrolyte leakage. For the second study, we developed a bifunctional electrocatalyst to promote the oxygen reactions in Zn-air batteries and achieve an electrically rechargeable configuration. The electrocatalyst was fabricated with Co₃O₄ particles attached to a functionalized carbon support.

The second half of the thesis is focused on the catalytic methanation of CO. This process allows the reduction of the main greenhouse gas, through the power-to-gas technology. Renewable energy can be used to power a reactor where the CO/CO2 is reduced to methane, which can be transported and stored in current systems. We considered Ni-based catalysts and carbon-based supports with the purpose of improving the CO conversion, the selectivity to CH4, and the catalyst stability. This study first compares Ni supported on AC and Ni₃Sn supported on AC to determine the effectiveness of Sn as a carbon fiber suppressor. In a second step, the study describes the fabrication method and catalyst performance of a core-shell structure using silica spheres grown on SWCNTs coated with the catalysts Ni₃Sn and FeNi₃ to improve the thermal stability and catalyst activity.