The energy transition to Zero carbon emissions started, and hydrogen is playing a very important role as replacement of the conventional fossil fuels, together with the large research and development in portable and stationary electrochemical energy storage devices as Li and Redox Flow batteries (RFB). An important aspect for these technologies is the materials used; RFBs store the energy in the electrolyte, requiring the use of porous electrodes with high surface are to maximise the electrolyte utilisation. For the Li Batteries, we will focus on the emerging Lithium Sulfur (Li-S), a carbon porous material is required in the cathode, which can accommodate the sulfur expansion during the charge and discharge, and as well avoid the polysulfides shuttle effect. An interesting material that can tackle this issue are carbon aerogels (CAGs), which are hierarchical carbon materials with tuneable porosity. The porosity and structure of these materials can be very easily tuned, changing the synthetic conditions, for each application.

In RFBs, to improve the performance and utilisation of the electrolyte can be done by reducing the thickness of the electrodes. However, some challenges need to be addressed, as mechanical properties, a good porosity and surface area. The CAGs, can be easily growth over different supports as carbon papers and carbon cloths, being in both cases, around 10 times thinner, compared with the standard graphite felts used in RFB. We had studied a series of these thinner electrodes, using carbon paper as support in all-Vanadium RFB, having a very interesting results in the behaviour of the different electrodes prepared [1].

The flexibility in the synthesis of these materials, give us a chance to use them as cathodes for Li-S batteries. In this case, we growth the CAGs in thinner electrodes successfully. In addition, we modify the CAGs doping them with Nitrogen and as well with Fe, trying to obtain a supported high porous single atom catalyst. We studied the electrodes in coin cell batteries to understand the performance and cyclability. In parallel, we started to analyse the CAGs powders and single atom catalyst with different metals in RDE and RRDE [2], trying to get a protocol to benchmark catalyst and materials for the sulfur reactions and understanding his kinetics in the oxidation and reduction.  

Other important actor for the zero-carbon energy system pointed out at the beginning is the H₂. A very important aspect is to develop materials for an efficient hydrogen production using renewable energies (Green H₂), which requires the use of electrolysers to split the water. The major problem for the electrolysers is within the anode, as they use Iridium (Ir), being not very abundant, restricting the large-scale production. However, there is other alternative, the alkaline electrolysers, in which the Ir can be replaced by other metals, more abundant on Earth. A very interesting materials to explore for the alkaline electrolysers are the transition metal phosphides, as they have a very interesting activity for the oxygen reactions with a good corrosion resistance characteristic [3].

Using H₂ for energy conversion, we need to mention Fuel Cells, focusing on the low temperature PEMFC, they are electrochemical devices that convert H₂ and O₂ in electricity and water. This system cannot be reversible due to the slow and complicated kinetics in the O₂ reactions. But replacing it with a fast and reversible species used in RFB, give us a very interesting and flexible electrochemical energy storage system, known as hybrid redox flow batteries. For these devices the cathode side it is quite flexible, having the possibility to use an organic molecule [4], vanadium [5] or manganese [6].