Electrocatalytic activity and stability of niobium-doped titanium oxide supported platinum catalyst for polymer electrolyte membrane fuel cells

Rutile phase niobium-doped titanium oxide [NbxTi(1 − x)O2, x = 0.25] with a high electrical conductivity (1.11 S cm−1) was synthesized and investigated as a cathode catalyst support material for polymer electrolyte membrane fuel cells (PEMFCs). The TEM image of the Pt/NbxTi(1 − x)O2 catalyst revealed that Pt particles (dPt = 3–4 nm) were deposited on the NbxTi(1 − x)O2 support using a borohydride reduction method. The Pt/NbxTi(1 − x)O2 catalyst showed comparable oxygen reduction reaction (ORR) activity to that of a commercial Pt/C catalyst (E-TEK) when tested in rotating ring-disk electrode (RRDE). The results of an accelerated durability test (ADT, continuous cycling between 0.6 and 1.4 V) in RRDE indicated high stability for the Pt/NbxTi(1 − x)O2 electrocatalysts at high potentials in terms of minimum loss in Pt electrochemical surface area (ECSA). Furthermore, the Pt/NbxTi(1 − x)O2 showed nearly 10-fold higher ORR activity after potential cycling tests when compared to the Pt/C catalyst (1.19 and 0.13 mA cm−2 for Pt/NbxTi(1 − x)O2 and Pt/C, respectively). The Pt/C catalyst showed no activity in fuel cell testing after 1000 cycles due to severe carbon corrosion and subsequent disintegration of the catalyst layer. Conversely, the Pt/NbxTi(1 − x)O2 catalyst showed only a small voltage loss (0.11 V at 0.6 A cm−2) even after 3000 cycles. Based on the ADT results, the Pt/NbxTi(1 − x)O2 electrocatalyst synthesized in this investigation offers a new approach to improve the reliability and durability of PEM-based fuel cell cathode catalysts.