TiO2-modified CNx nanowires as a Pt electrocatalyst support with high activity and durability for the oxygen reduction reaction

Abstract

A Pt/TiO₂-modified carbon nitride nanofiber (Pt/TiO₂-CN_x) catalyst has been synthesized by a chemical method for the oxygen reduction reaction (ORR). The material characteristics confirmed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) have indicated that the TiO₂-CN_x nanowires have a diameter of about 35–85 nm, the TiO₂ nanoparticles are embedded in CN_x nanowires and Pt nanoparticles are about 2.21 nm in size. The X-ray photoelectron spectra (XPS) show that Ti has a shift in the binding energy of Ti 2p, implying suboxide formation. Pt/0.2 g TiO₂-CN_x has about 3% loss in the (electrochemical surface area) ESA after 1000 cycles, however, the Pt/C catalyst has about 50.8% loss in the ESA. Pt/0.2 g TiO₂-CN_x has much better activity than Pt/C, which is proposed to be due to the high total surface area of Pt. The durability test shows that the Pt/0.2 g TiO₂-CN_x catalyst has no loss of activity after 5000 cycles. After 5000 cycles, the average size of Pt nanoparticles and the peaks of Pt 4f almost remain unchanged. The high durability of Pt/0.2 g TiO₂-CN_x is attributed to the corrosion-resistance of 0.2 g TiO₂-CN_x nanowires support and the good interaction between the 0.2 g TiO₂-CN_x support and the Pt nanoparticles.