Tunable nano-distribution of Pt on TiO2 nanotubes by atomic compression control for high-efficient oxygen reduction reaction

Abstract

Achieving cost-competitive catalysts with low Pt utilization and improving the durability caused by the corrosion of supports in the catalysts must be solved for the high activity in the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Here, we show an innovative technique to synthesize unique nanotube supports for the ORR catalysts based on the combination of experimental and theoretical studies. The method precisely controls the atomic morphology of TiO2 nanotubes by a small amount of atomic substitution, maximizing their efficiency as catalyst supports. The spontaneous change in the size and dispersibility of the Pt nanoparticles appears by only small lattice contraction on the metal-doped TiO2 (M-TiO2) nanotubes. To study this phenomenon, various dopants such as V, Nb, and Cr were added to the M-TiO2 nanotubes. The compression arising out of each metal-support interaction resulted in the diverse shape of the nanoparticles on similar supports, which is revealed based on the X-ray absorption fine structure (XAFS) and the density-functional-theory (DFT) calculations. Based on a comprehensive understanding of inter-and intracrystal interactions in the small substitution doping process, we can control the size and dispersibility of the Pt nanoparticles, catalytic activity, and durability of catalysts for ORR.