Controlled Growth of Palladium Nanoparticles on Graphene Nanoplatelets via Scalable Atmospheric Pressure Atomic Layer Deposition

Abstract

We demonstrate the deposition of crystalline palladium nanoparticles on graphene nanoplatelets (Pd/graphene) via atmospheric pressure atomic layer deposition (ALD) carried out in a fluidized bed reactor. The nucleation and growth of Pd nanoparticles on the inert graphene surface was enabled by applying an ozone pretreatment step, without significantly affecting the graphene crystalline structure. Uniform nucleation on both basal planes and edges of the graphene was obtained. The Pd loading and dispersion as well as the average particle size could be controlled by varying the number of ALD cycles. By analyzing the evolution of the particle size distribution and spatial density, we obtained insights into the nucleation and growth of Pd ALD on graphene. Furthermore, by shortening the pretreatment time, selective growth of Pd nanoparticles on the edges of the graphene was achieved. The Pd/graphene fabricated with our method showed a significantly lower level of impurities compared to the Pd/graphene synthesized by wet chemistry routes. Our approach provides a 100% solvent-free, controllable and scalable process for producing the bulk quantities of Pd/graphene required for practical applications in, for example, catalysis.

Understanding and Controlling the Aggregative Growth of Platinum Nanoparticles in Atomic Layer Deposition: An Avenue to Size Selection

“…10 Atomic layer deposition (ALD) is an established thin-film deposition technique that has recently seen use in the synthesis of supported NPs with very promising results in terms of control over the NP size. 2 , 4 , 11 − 14 By relying on the cyclic repetition of self-limiting gas–solid reactions, ALD boasts digital control and atomic-level precision over the amount of material being deposited. 4 , 11 , 15 While originally developed for flat substrates, ALD is readily scalable to high-surface-area substrates thanks to its solvent-free and surface-driven nature.…”

“… 4 , 16 − 21 As a result, ALD of NPs has been reported with different PSDs, and the growth mechanisms leading to these different PSDs are still under debate. 1 , 2 , 4 , 12 , 14 , 17 , 20 − 23 …”

“…We have recently shown that ALD of Pd NPs results in broad right-skewed PSDs and a reduction in the NPs density with the number of cycles that is consistent with NP sintering via NP diffusion and coalescence. 14 Even if this suggests that Smoluchowski aggregation is a governing growth mechanism also in ALD of NPs, many questions remain, in particular: Can we understand NP growth in terms of elementary atomistic processes and thus identify the governing NP growth mechanisms among layer-by-layer growth due to direct precursor chemisorption, single atom deposition on the substrate followed by attachment to NPs, Ostwald ripening, and NP diffusion and coalescence? And, can we steer the growth so as to achieve size selection and control the size simply by the number of cycles?…”

Surface modification and functionalization of powder materials by atomic layer deposition: a review

“…In another case, Pd nanoparticles were deposited onto graphene (GE) nanoplatelets using a FBR at atmospheric pressure. 17 The Pd/GE obtained by atmospheric pressure ALD showed lower impurity content, better dispersion and more uniform distribution of Pd nanoparticles. Obviously, it will be much more convenient to scale-up the ALD process under atmospheric pressure, however, efficient supplying and removing of precursors and avoiding side reactions are still challenging under atmospheric pressure.…”

Atmospheric pressure atomic layer deposition for tight ceramic nanofiltration membranes: Synthesis and application in water purification

“…This enables an easier scale-up approach towards large-volume manufacturing. Although APALD has already been demonstrated for coating (nano-)particles [24][25][26] and nonporous planar surfaces [27], this technique has not yet been applied to deposit thin films on porous ceramic membranes.…”