Structural disorder in ORR electrocatalysis: operation mode, practical descriptors to quantify and foreseen challenges
Résumé
Due to strain and ligand effects, the simultaneous presence of concave and convex surfaces and their highly-defective nanostructure (atomic vacancies, grain boundaries), highly defective hollow PtNi/C electrocatalysts have proven to enhance remarkably the oxygen reduction reaction (ORR) kinetics [1,2]. Likewise, PtNi aerogel [3], jagged PtNi nanowires [4,5] feature both high concentration of structural defects and enhanced ORR activity. On the other hand, and inspired from single crystal approach, nanostructured octahedral-shaped PtNi/C electrocatalysts exhibiting only Pt(111) facets are among the most active ORR electrocatalysts [6,7]. This presentation will show how structure-activity-stability relationships of these two classes of materials can be unified via two descriptors derived from structural and electrochemical parameters respectively [8,9]. A special emphasis will be given on the stability trends of these two families of ORR electrocatalysts.