Electrodes Based on Carbon Aerogels Partially Graphitized by Doping with Transition Metals for Oxygen Reduction Reaction

A series of carbon aerogels doped with iron, cobalt and nickel have been prepared. Metal nanoparticles very well dispersed into the carbon matrix catalyze the formation of graphitic clusters around them. Samples with different Ni content are obtained to test the influence of the metal loading. All aerogels have been characterized to analyze their textural properties, surface chemistry and crystal structures. These metal-doped aerogels have a very well-developed porosity, making their mesoporosity remarkable. Ni-doped aerogels are the ones with the largest surface area and the smallest graphitization. They also present larger mesopore volumes than Co- and Fe-doped aerogels. These materials are tested as electro-catalysts for the oxygen reduction reaction. Results show a clear and strong influence of the carbonaceous structure on the whole electro-catalytic behavior of the aerogels. Regarding the type of metal doping, aerogel doped with Co is the most active one, followed by Ni- and Fe-doped aerogels, respectively. As the Ni content is larger, the kinetic current densities increase. Comparatively, among the different doping metals, the results obtained with Ni are especially remarkable.