Distinct dependence on size of Pt and Rh nanoclusters on graphene/Pt(111) in the decomposition of methanol-d4

Abstract

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.

Experimental and Theoretical Insights into Transition-Metal (Mo, Fe) Codoping in a Bifunctional Nickel Phosphide Microsphere Catalyst for Enhanced Overall Water Splitting

“…All ab initio calculations were performed with the Vienna Ab initio Simulation Package (VASP 5.4.1). − The projector augmented wave method was employed along with the generalized gradient approximation based on the Perdew–Burke–Ernzerhof (PBE) functional using a plane-wave cutoff energy of 500 eV. − The lattice constants and internal atomic positions were fully optimized until the residual forces were below 0.04 eV/Å. To avoid interactions between the layers, the vacuum slab space of a unit cell in the z -direction was set as 15 Å.…”

Catalyzed Decomposition of Methanol-d4 on Vanadium Nanoclusters Supported on an Ultrathin Film of Al2O3/NiAl(100)

“…Upon adsorption of CD 3 OD at 100 K, the spectra show several characteristic absorption lines; that at 984 cm –1 is assigned to the C–O stretching (ν­(CO)) and that at 1125 cm –1 is assigned to the CD 3 symmetric deformation (δ s (CD 3 )) of CD 3 OD* (top spectrum in Figure a); a broad absorption line centered at 2440 cm –1 is assigned to O-D stretching (ν­(OD)), a doublet at 2243 and 2214 cm –1 is assigned to the combination ν as (CD 3 ) + 2δ s (CD 3 ), and a narrow line at 2071 cm –1 is assigned to symmetric CD 3 stretch (ν s (CD 3 )) of CD 3 OD* (top spectrum in Figure b). − These features resemble closely those of CD 3 OD* on supported Pt clusters, Au–Pt, and Au–Rh bimetallic clusters. ,, When the temperature was increased to 135 K, all absorption lines attenuated significantly because multilayer CD 3 OD* desorbed from the surface; a slight red shift of δ s (CD 3 ) and ν­(CO) lines resulted because the signals were contributed primarily by monolayer CD 3 OD* (third spectrum in Figure a). At 155 K, the signals of ν­(OD) and ν as (CD 3 ) + 2δ s (CD 3 ) almost vanished because CD 3 OD* decreased and the O–D stretching motion of monolayer CD 3 OD* was nearly parallel to the surface. ,, On annealing further to 175–225 K, the spectra altered significantly; the δ s (CD 3 ) and ν s (CD 3 ) lines shifted negatively to 1103 and 2056 cm –1 , respectively, indicating the formation of CD 3 O* and hence the cleavage of the O–D bond of CD 3 OD*; ,, a new absorption feature appeared at about 1023 cm –1 , ascribed to the ωCD 2 mode of CD 2 O* . The negative shifts of δ s (CD 3 ) and ν s (CD 3 ) lines were observed for investigated V coverages ≥0.5 ML whereas the new absorption was observed only for 4.0 ML V. As the orientations of CD 3 O* and CD 2 O* were unknown, a precise estimation or comparison of their quantities was difficult.…”

Enhanced Electrocatalytic Oxidation of Methanol on Pt‐Decorated Bi2WO6/Graphene Nanosheets with Visible Light Assistance

“…Owing to its high electron transfer rate and specific surface area, RGO is extensively applied in the field of physics, chemistry, and materials science. [17][18][19][20][21][22][23][24] Moreover, it is also proved that the unique structure of RGO not only promotes sufficient dispersibility for noble metal materials, but also provides more reactive sites and electron transport channel for the catalyst, which comprehensively promote the improvement of catalyst performance. Furthermore, RGO could be taken as the excellent conductive carrier, which contributes to the transfer of photogenic electrons from the surface of semiconductors to the electrode and thereby promotes the expression of electrical signals.…”