Synthesis of Pt/TiO[sub 2] Nanotube Catalysts for Cathodic Oxygen Reduction

Robust titanium oxide nanotube (TONT) arrays were formed by electrochemical anodization on various sample shapes (rod, screw, and foil), which facilitates versatility for electrode applications. From scanning electron microscopy images, it is clearly noted that irrespective of the shape of the sample, the self-organized TONT structure stands perpendicular to the surface with approximately the same width, hole size, and length, leading to its high surface area. To evaluate various TONT samples as catalyst supports for oxygen reduction in acidic solutions, a platinum (Pt) layer was deposited by both dc sputtering and evaporation. From the microscopic comparison between the sputtered and evaporated features of Pt/TONT catalysts, we found that the sputtered Pt is more conformal to the TONT surface morphology than the evaporated one, and this preserves the surface area increased by TONT formation. The cyclic voltammogram obtained from the sputtered Pt/TONT showed a somewhat higher potential value for initiating oxygen reduction than for the evaporated Pt/TONT. This is attributed to better electrochemical catalytic activity enhanced by the high surface area of the Pt layer.