2D Platinum Network ORR Catalyst on Carbon and Niobium Oxide Hybrid Support

2D platinum network catalyst on graphitic carbon and amorphous NbO_x hybrid support has been synthesized by Arc Plasma Deposition (APD) method. The 2D platinum structure on the conductive, corrosion resistant amorphous metal oxide significantly increases the catalyst stability under RDE accelerated stress tests. RDE and 5cm²MEA single cell test results showed that the catalyst has higher specific and mass activities than those of conventionally prepared platinum on graphitic carbon (Pt/C) catalyst. The microstructures of the catalyst were characterized by transmission electron microscopy (TEM).

Amorphous NbO_x conductive metal oxide was deposited from either Nb₂O₅ in Ar or Nb in a gas mixture of 30 vol.% of O₂ in Ar onto carbon particles by using Arc Plasma Deposition (APD) system (Ulvac-Riko, Inc). The obtained NbO_x on carbon particle are isolated amorphous islands, with the value of x between 1 and 2.5. When Pt was deposited onto the formed NbO_x islands, a platinum 2D nano-network was obtained, as schematically shown in Figure 1. The platinum particles with about 5 nm size can be uniformly deposited on the support NbO_x and carbon. Figure 2 shows the percentage change of ECSA and mass activity under AST using square wave 1.0V~1.5V for carbon corrosion (a) and 0.1V~1.0V for Pt (b). The specific (SA) and mass activities (MA) are about 400 m A/cm²_Pt and 350A/g_Pt, respectively. The accelerated stress tests show that the durability of the catalyst is about 3~5 times higher than those of synthesized Pt on carbon catalyst through wet chemical methods under the same carbon corrosion and platinum stress conditions. The polarization curve and EIS data of Pt/C and Pt/NbO_x/C on a 5 cm² single cell are shown in Figure 3. Pt/NbOx/C cell with 0.07mg/cm² Pt loading and Pt/C cells with 0.19mg/cm² Pt loading have a similar polarization curve.