Sub-nanometer thin TiO2-coating on carbon support for boosting oxygen reduction activity and durability of Pt nanoparticles

Abstract

The lack of highly efficient and stable electrocatalysts for oxygen reduction reaction (ORR) has been hindering the advances in proton exchange membrane fuel cells (PEMFCs). Harnessing the strong metal–support interactions (SMSI) effects at the interface between a metal oxide and a noble metal is one approach investigated to address these issues. In this work, TiO2 coating with 0.6 nm in thickness, uniformly formed on the entire surface of a carbon material is synthesized by a sonochemical reaction method. Deposition of Pt nanoparticles (NPs) on TiO2 coated carbon (TiO2/C) produces Pt/TiO2/C catalysts with enhanced activity and durability for ORR. Pt/TiO2/C(U) whose Pt NPs are formed by sonochemical reaction shows mass activity (MA) and specific activity (SA) 2.9 and 2.6 times, respectively, higher than Pt/C catalyst. More importantly, Pt/TiO2/C(U) catalyst exhibits a superior long-term durability. After 50,000 cycles of durability test, it retains 51.4 %/61.3% of initial MA/SA. Pt/TiO2/C(R) whose Pt NPs are formed by chemical reduction also shows enhanced activity and durability than Pt/C, but with less extents than Pt/TiO2/C(U). The significantly enhanced ORR performance of Pt/TiO2/C catalysts is attributed to the SMSI effect between TiO2 coating and Pt NPs plus bifunctional mechanism from the TiO2 surface around Pt NPs. The enhance durability can be explained as the protection of carbon by chemically inert TiO2 coating.