Self-supported Pt-CoO networks combining high specific activity with high surface area for oxygen reduction.

Sievers, Gustav W; Jensen, Anders W; Quinson, Jonathan; Zana, Alessandro; Bizzotto, Francesco; Oezaslan, Mehtap; Dworzak, Alexandra; Kirkensgaard, Jacob J K; Smitshuysen, Thomas E L; Kadkhodazadeh, Shima; Juelsholt, Mikkel; Jensen, Kirsten M Ø; Anklam, Kirsten; Wan, Hao; Schäfer, Jan; Čépe, Klára; Escudero-Escribano, María; Rossmeisl, Jan; Quade, Antje; Brüser, Volker; Arenz, Matthias

Several concepts for platinum-based catalysts for the oxygen reduction reaction (ORR) are presented that exceed the US Department of Energy targets for Pt-related ORR mass activity. Most concepts achieve their high ORR activity by increasing the Pt specific activity at the expense of a lower electrochemically active surface area (ECSA). In the potential region controlled by kinetics, such a lower ECSA is counterbalanced by the high specific activity. At higher overpotentials, however, which are often applied in real systems, a low ECSA leads to limitations in the reaction rate not by kinetics, but by mass transport. Here we report on self-supported platinum-cobalt oxide networks that combine a high specific activity with a high ECSA. The high ECSA is achieved by a platinum-cobalt oxide bone nanostructure that exhibits unprecedentedly high mass activity for self-supported ORR catalysts. This concept promises a stable fuel-cell operation at high temperature, high current density and low humidification.