ne of the biggest challenges for materials science is to design facile routes to structurally complex materials, which is particularly important for global applications such as fuel cells. Doped nanostructured carbons are targeted as noble metal-free electrocatalysts for this purpose. Their intended widespread use, however, necessitates simple and robust preparation methods that do not compromise on material performance.

Here, we demonstrate a versatile one-pot synthesis of nitrogen-doped carbons that exploits the templating ability of biological polymers. Starting with just metal nitrates and gelatin, multiphase C/Fe3C/MgO nanomaterials are formed, which are then etched to produce active carbon electrocatalysts with accessible trimodal porosity. These show remarkable performance in the oxygen reduction reaction – a key process in proton exchange membrane fuel cells. The activity is comparable to commercial platinum catalysts and shows improved stability with reduced crossover effects. This simple method offers a new route to widely applicable porous multicomponent nanocomposites.

—Schnepp et al.

The new material performs so well because the iron and magnesium salts cause the gelatin to foam, creating a sponge-like structure. When this is heated, nanoparticles of iron carbide form inside the sponge. These nanoparticles can be easily dissolved, leaving tiny holes rather like hollow capsules, in the walls of the sponge. Together, the capsules and the sponge-structure create an extremely high surface area, which is crucial for allowing the gaseous reactants to flow through the fuel cell catalyst.

Unlike platinum, which is rare, our new material is made up of the abundant and cheap elements, iron and magnesium. By combining these with gelatin we have made an effective material which shows remarkable performance in generating electricity comparable to a commercial platinum catalyst. The key is that the gelatin material is not only cheap, but it’s extremely easy to make.

—Dr. Zoe Schnepp, Birmingham Fellow from the University of Birmingham’s School of Chemistry,

Resources

• Zoe Schnepp, Yuanjian Zhang, Martin J. Hollamby, Brian R. Pauw, Masahiko Tanaka, Yoshitaka Matsushita and Yoshio Sakka (2013) Doped-carbon electrocatalysts with trimodal porosity from a homogeneous polypeptide gel. J. Mater. Chem. A doi: 10.1039/C3TA12996A