Atomic layer deposition (ALD) has emerged as a powerful technique for synthesizing catalytic nanomaterials with exceptional control over particle size, composition, and distribution. Unlike conventional methods such as impregnation or colloidal synthesis, ALD offers sub-nanometer precision in depositing active metal nanoparticles (e.g., Pt, Pd) on high-surface-area supports. This precision is critical for optimizing catalytic performance, where activity and selectivity often depend on the atomic-scale arrangement of metal sites.

The self-limiting nature of ALD reactions enables the controlled growth of catalytic materials one atomic layer at a time. By alternating exposures of metal precursors and co-reactants, ALD can deposit uniform metal nanoparticles with narrow size distributions. For example, Pt nanoparticles synthesized via ALD typically exhibit sizes tunable between 1–5 nm, with standard deviations below 0.5 nm. Such precision is difficult to achieve with wet-chemical methods, where nucleation and growth processes are less controlled. The ability to tailor particle size at this scale is particularly valuable for catalysis, where turnover frequencies and selectivity are highly sensitive to particle diameter.

Support interactions play a crucial role in determining the stability and reactivity of ALD-synthesized catalytic nanomaterials. ALD allows for the deliberate engineering of metal-support interfaces, which can influence electronic properties and adsorption energetics. For instance, depositing Pt on Al2O3 via ALD results in stronger metal-support interactions compared to traditional impregnation, reducing sintering during high-temperature reactions. The choice of support material—whether oxide (e.g., TiO2, CeO2), carbon, or zeolites—can be optimized to enhance dispersion and electronic modulation of the active phase. ALD’s conformal coating capability ensures uniform deposition even on porous or high-aspect-ratio supports, eliminating inhomogeneities that plague other techniques.

Atomic-scale uniformity is another hallmark of ALD-derived catalysts. The sequential pulsing of precursors ensures that each active site is nearly identical, minimizing variations in coordination environment that can lead to side reactions. This is especially important for bimetallic systems, where ALD can deposit alternating layers of two metals (e.g., Pt-Pd) with stoichiometric control at the monolayer level. Such precision enables the systematic study of alloy effects on catalytic behavior, such as tuning the d-band center to optimize adsorption energies for specific reactions.

One of ALD’s unique advantages is its ability to create overcoats or protective layers that stabilize catalytic nanoparticles without blocking active sites. Ultrathin oxide layers (e.g., Al2O3, TiO2) applied via ALD can suppress sintering while permitting reactant access to the metal surface. These overcoats, often just a few angstroms thick, act as molecular sieves, selectively allowing small reactants to reach the metal while preventing agglomeration. Studies have shown that ALD-overcoated Pt catalysts maintain activity over extended periods in harsh environments, such as high-temperature oxidation or hydrocarbon reforming.

The digital nature of ALD also facilitates the synthesis of complex architectures, such as core-shell or yolk-shell nanoparticles, with precise control over shell thickness and composition. For example, Pd@CeO2 core-shell structures synthesized by ALD exhibit enhanced activity for methane combustion due to the intimate contact between Pd and the reducible CeO2 shell. The ability to engineer such structures layer-by-layer opens new avenues for designing catalysts with tailored interfacial properties.

Despite these advantages, ALD faces challenges in scaling up for industrial catalyst production. The slow deposition rate and need for high-vacuum conditions can increase costs compared to conventional methods. However, for applications requiring ultra-precise control—such as fuel cell electrodes or selective hydrogenation catalysts—the benefits of ALD often outweigh these limitations. Recent advances in spatial ALD and fluidized-bed reactors aim to address scalability issues while maintaining atomic-level precision.

In summary, ALD provides unparalleled control over the synthesis of catalytic nanomaterials, enabling the design of highly uniform, stable, and active catalysts. Its ability to tailor particle size, composition, and support interactions at the atomic scale makes it an indispensable tool for advancing catalytic science, particularly where conventional methods fall short in precision or reproducibility. As ALD techniques continue to evolve, their role in developing next-generation catalysts for energy and chemical processes will only expand.