Amorphous carbons can be “doped” with a number of heteroatoms, leading to a large variety of chemical functionalities. Moreover, the doped carbons can be shaped morphologically on different size scales. The chemical and morphological structure, both influence the electrochemical activity of those materials and make them interesting candidates for modern energy-related applications. In the presentation, I will show results on structure-performance relations on mass-transport and activity for precious-metal free electrocatalysts and discuss the role of structure in hard carbon anodes for sodium ion batteries. 

Proton-exchange membrane fuel cells are amongst the most promising energy conversion technologies today. Herein non-precious iron-coordinated nitrogen doped carbons (Fe-N-Cs) are very promising alternatives for Pt-based cathode catalysts. The early reports on the application of such materials date back to the 1960´s when Jasinski demonstrated that - similar to natural porphyrins - N-coordinated transition metal complexes can be active sites for the ORR. The preparation of these catalysts was strongly optimized over the years; still they typically remain with harsh reaction conditions that complicate the selective formation of active FeN₄ sites. The employment of pyrolytic temperatures has been a dogma for the synthesis of MN₄ sites, however coming with unfavorable side reactions. We recently introduced a mild procedure, which is conservative toward the carbon support and leads to active-site formation at low temperatures in a wet-chemical step, essentially decoupling the preparation of nitrogen doped carbons (NCs) from the preparation of the active sites.

The key concept therein is the so-called active site imprinting into the NC using the less reactive template ions Mg²⁺ or Zn²⁺. The presentation will introduce the concept of active site imprinting with a focus on Fe-N-C electrocatalyst development and testing. The broad potential of the synthetic approach will be exemplified by recent results, including the selective synthesis of tetrapyrrolic single site catalysts, the assignment of the role of the transition metal compared to the carbon scaffold and a facile method to evaluate specific activity.

In sodium ion batteries subnanometer sized pores are utilized for storage of sodium in disordered carbon anodes. The adsorption mechanism is not stoichiometric, hence the ultimate potential of hard carbon anodes is yet unknown. It will be discussed what may be estimated as capacity limit and what are the challenges in achieving them.