The main functional characteristics of electrocatalysts are their activity in reactions occurring in the catalytic layers of low-temperature fuel cells, as well as stability (maintaining activity during the operation of the fuel cell or electrolyzer). Direct comparison of these characteristics is difficult, since their values depend not only on the composition and structure of the catalysts themselves, but also on the design and composition of the porous catalytic layer, temperature, pressure and humidity of gases, some other factors. Therefore, manufacturers often indicate the values ​​of parameters characterizing the structure of Pt/C electrocatalysts: the average size of platinum nanoparticles, their spatial and size distribution; electrochemically active surface area. PEM microphotographs of fragments of their surface give a good understanding of ​​the microstructure of catalysts too.

Below is a table describing the composition and structure of catalysts produced by PROMETHEUS R&D, LLC using Vulcan XC72 and Ketjen black EC300 J carbon supports.