Role of Acid Treatment of the Carbon Support in the Growth of Atomic‐Layer‐Deposited Pt Nanoparticles for PEMFC Fabrication

Abstract Ultrathin films or particles of atomic layer deposition (ALD) on high surface can improve the activity and durability of catalyst fields, so depending on the surface state, the ALD growth mechanism on porous materials should be systematically investigated and optimized to improve their characteristics of catalysts. Herein, a Pt catalyst used in polymer electrode membrane fuel cell (PEMFC) applications is synthesized through fluidized‐bed‐reactor ALD on carbon black whose surface is modified through treatment with citric acid. The functional groups, analyzed through X‐ray photoelectron spectroscopy (XPS), are found to be maximized after 60 min of acid treatment with stirring. Compared with bare carbon (untreated), the acid‐treated carbon presents rich oxidized functional groups and abundant defects but lower surface areas and pore volumes. After ALD Pt deposition, highly dense, uniform, and well‐dispersed Pt nanoparticles (NPs) are observed on the carbon black subjected to acid treatment, because of the favorable surface modifications for ALD growth resulting from the acid treatment. The ALD‐Pt NPs on the acid‐treated carbon exhibit larger electrochemical active surface areas, improved oxygen reduction reactions, and PEMFC performances, when compared with that of NPs on bare carbon with similar Pt weight loading.