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Pt and Rh nanoclusters, grown on deposition of Pt and Rh vapors onto graphene/Pt(111), show separate reactivity toward the decomposition of methanol-d4. The Pt (Rh) clusters had a mean diameter 2.0–3.5 nm (2.1–4.0 nm) and height 0.45–0.94 nm (0.41–0.9 nm) evolving with the coverage; they were structurally ordered, having an fcc phase and growing in (111) orientation, and had lattice constants similar to their bulk values. Methanol-d4 on the Pt clusters did not decompose but desorbed mostly, disparate from that on Pt(111) surface; the disparity arose as the adsorption energies of methanol-d4 on most surface sites of the Pt clusters became smaller than their single crystal counterpart. This size effect, nevertheless, did not apply on the Rh clusters, despite their similar atomic stacking; the Rh clusters showed a reactivity similar to that of the Rh(111) surface because the adsorption energies of methanol-d4 on both Rh clusters and Rh(111) are comparable. The distinct size dependence was rationalized through their electronic structures and charge distribution of Fukui function mapping. Our results suggest that reactive transition metals do not necessarily become more reactive while they are scaled down to nanoscale; their reactivity evolves with their size in a manner largely dependent on their electronic nature.

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Thin films of oxide, sulfide, and oxysulfide of zinc can be deposited with atomic layer deposition (ALD) using diethylzinc with H2O and H2S. While the atomic ratio between O and S in zinc oxysulfide can be arbitrarily tuned by varying the supercycles of oxide and sulfide ALD, it is known that the fraction of S incorporated in the film is higher than its ratio in the reactant pulses. To understand the mechanism controlling the composition of ALD zinc oxysulfide thin films, its surface chemical reactions are investigated using density functional theory calculations. It is observed that all half reactions of both oxide and sulfide ALD would be facile and spontaneous, while the reactions for deposition of sulfide are more favorable over those for oxide. Furthermore, an *OH group on the surface can be easily substituted into *SH by reaction with H2S, but the inverse reaction is less likely. As a result, excess S can be contained in the Zn(O,S) ALD thin films due to the exchange reactions between surface moieties. The authors suggest that the differences in the bond energies of O–H versus S–H moieties are the key governing factor for the composition of ALD zinc oxysulfide films.