In Situ Engineering of a Metal Oxide Protective Layer into Pt/Carbon Fuel-Cell Catalysts by Atomic Layer Deposition

(PEMFC) systems has emerged as a critical issue. A thin metal oxide layer coated with Pt/carbon via ALD (atomic layer deposition) is one of the potential approaches for preserving electrochemical activity; however, the exact interfacial effects of metal oxide on enhancing PEMFC durability are unclear. Herein, interfacial engineering of the TiO2 layers within the in situ-synthesized Pt/carbon catalysts (Pt/TiO2/C and TiO2/Pt/C) was studied using fluidized bed reactor (FBR) ALD to investigate the exact effects of the catalysts. For the Pt/TiO2/C catalyst, the TiO2 layer was first conformally coated on the carbon surfaces, whereas for TiO2/Pt/C, the TiO2 layer was selectively formed on the Pt NP surface via the ALD mechanism. The Pt/TiO2/C catalyst has a higher Pt loading with suppressed micropores due to the introduction of the TiO2 layer on the carbon support, whereas the TiO2/Pt/C catalyst remained in the 2-3 nm mesopores. The electrochemical durability of both ALD catalysts is superior to that of the commercial Pt catalyst. Encapsulating the TiO2 layer on the Pt surface specializing in blocking Pt dissolution resulted in better long-term stability of the electrochemical characteristics compared to the stability of those of Pt/TiO2/ C, which especially showed the better initial performance of the electrochemically active surface area, oxygen reduction reaction, and PEMFC single-cell performance. This study provides the direction and steps toward an efficient nanostructure design of metal oxide by ALD in most catalyst fields.