Nils Heppe's research while affiliated with Technische Universität Darmstadt and other places

... Possessing four pyrrole units interconnected toeach other via methane bridges and a large π-conjugated electron system, all porphyrin derivatives can bind almost any known metal ions and be substituted by different functional moieties [26]. These intrinsic characteristics have provided great flexibility in engineering and designing surface-terminal functional groups, thereby enhancing the applicability of this class of molecule in electrocatalysis including HER and OER [27,28]. Thus far, metallated porphyrin-based catalysts with a metal center responsible for the catalytic activity have been exclusively investigated for water splitting [26,[29][30][31]. ...

... 38 Depending on the leading degradation mechanism different strategies were developed to inhibit activity losses, as the addition of small amounts of precious metals or the modification with fluorine. [39][40][41] Caution needs to be taken, when conclusions on stabilization strategies are only made on the basis of rotating (ring) disc electrode (R(R)DE) experiments rather than FC testing. While RRDE provides a good and fast platform to determine in a short period of time the kinetic current density and the hydrogen peroxide yield (if applied at low loading), these measurements are neither suited to identify mass transport limitations of the catalyst nor for fully understanding how to transfer conclusions on degradation from rotating disc electrode (RDE) to FC level. ...

... The same membrane in a methanol fuel cell was also studied by the same group 198 with a different bimetallic catalyst, Pd 3 Ag/C, which achieved a lower power density of 11.9 mW cm À2 at 60 C when 2 M methanol with 2 M KOH was used as the anode feed. Jurzinsky et al. 199 also obtained a power density of 14.3 mW cm À2 at 60 C with the same membrane in a fuel cell operating on 4 M methanol Pt/C with a comb-like ionomer anode catalyst and Pt/C on the cathode with oxygen feed. Kim et al. ...