Oxygen Reduction Reaction Activity and Electrochemical Stability of Thin-Film Bilayer Systems of Platinum on Niobium Oxide

We used electrochemical testing and theoretical calculations based on density functional theory (DFT) to examine the oxygen reduction reaction (ORR) activity of platinum electrocatalyst supported on several forms of niobium oxide. Bilayer electrocatalysts were synthesized in the form of 5 nm thick Pt layers (ca. 0.01 mg/cm 2 ), deposited on 5 or 10 nm thick niobium oxide and backed by glassy carbon (GC) electrodes. The NbO and NbO 2 supports enhance the specific electrochemical activity of Pt relative to the identically synthesized baseline system of Pt on GC but have no positive effect on the mass activity. The electrochemical stability of the Pt/NbO 2 bilayer system was investigated by potential cycling with up to 2500 cyclic voltammetry (CV) cycles. After 2500 cycles, data indicates minimal electrochemical area loss. With the use of DFT calculations, we have evaluated effects of oxygen incorporation on stability, electronic structure, and electrochemical activity of Pt|Nb x O y systems. Calculations predict a transfer of electronic charge density from Nb, NbO, and NbO 2 to Pt and a reverse case for Nb 2 O 5 . However, the experimental ORR activity does not follow the trends predicted by the d-band model.