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 MeCpPtMe₃and O₂. In this approach, the deposition temperature varies in a cyclic manner in accordance with the Pt precursor and the O₂exposure steps. In every ALD cycle, the MeCpPtMe₃exposure is carried out at either 150 or 200 °C, and the O₂exposure 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.

We tailored the size distribution of Pt nanoparticles (NPs) on graphene nanoplatelets at a given metal loading by using low-temperature atomic layer deposition carried out in a fluidized bed reactor operated at atmospheric pressure. The Pt NPs deposited at low temperature (100 °C) after 10 cycles were more active and stable towards the propene oxidation reaction than their high-temperature counterparts. Crucially, the gap in the catalytic performance was retained even after prolonged periods of time (>24 hours) at reaction temperatures as high as 450 °C. After exposure to such harsh conditions the Pt NPs deposited at 100 °C still retained a size distribution that is narrower than the one of the as-synthesized NPs obtained at 250 °C. The difference in performance correlated with the difference in the number of facet sites as estimated after the catalytic test. Our approach provides not only a viable route for the scalable synthesis of stable supported Pt NPs with tailored size distributions but also a tool for studying the structure-function relationship.