Size-Controlled and Sintering-Resistant Sub-3 nm Pt Nanoparticles on Graphene by Temperature-Variation Atomic Layer Deposition

Abstract

Noble metal nanoparticles (NPs), particularly platinum (Pt), are widely used in heterogeneous catalysis due to their exceptional activity. However, controlling their size and preventing sintering during synthesis remains a major challenge, especially when aiming for high dispersion and stability on supports such as graphene. Atomic layer deposition (ALD) has emerged as a promising method to address these issues, yet conventional processes often lead to broad particle size distributions (PSDs). This work introduces a new approach for the deposition of size-controlled and sintering-resistant Pt NPs on graphene by atmospheric-pressure ALD using MeCpPtMe₃ and O₂. In this approach, the deposition temperature varies in a cyclic manner in accordance with the Pt precursor and the O₂ exposure steps. In every ALD cycle, the MeCpPtMe₃ exposure is carried out at either 150 or 200 °C, and the O₂ exposure is at room temperature. The room-temperature step hinders the diffusion and coalescence of Pt NPs, resulting in significantly narrower PSDs compared to those achieved by the conventional ALD processes at 150 and 200 °C. Importantly, Pt NPs with narrower PSDs exhibit higher catalytic activity and improved stability, which are demonstrated for the propene oxidation reaction, despite having a significantly lower Pt loading. Our approach may open a new avenue toward the size-selection synthesis of noble metal NPs for catalytic applications.