Electrocatalytic activity and durability of Pt/NbO2 and Pt/Ti4O7 nanofibers for PEM fuel cell oxygen reduction reaction

In this paper, we report the synthesis of both NbO2 and Ti4O7 nanofibers using an electrospinning technique in an effort to use metal oxides as a possible replacement for carbon as PEM fuel cell catalyst supports. The synthesized nanofibers are physically characterized using several methods including XRD, SEM, TEM, BET, ICP-MS as well as XPS. The thermal, chemical, and electrochemical stabilities as well as the electronic conductivities of these two supports are also evaluated in order to check their feasibility as catalyst supports in the temperature range of 95–200 °C. Two catalysts, 20-wt% Pt/NbO2 and 20-wt% Pt/Ti4O7, are prepared and tested for both ORR mass activity and stability in acidic solution. XPS measurements of samples analyzed before and after the durability tests suggest the formation of electronically insulating surface oxides, which can be partially responsible for both low ORR mass activity and catalyst durability.