Charge Transfer Stabilization of Late Transition Metal Oxide Nanoparticles on a Layered Niobate Support

Abstract

The interfacial interactions between late transition metal/metal oxide nanoparticles and oxide supports impact catalysts’ activity and stability. Here, we report the use of isothermal titration calorimetry (ITC), electron microscopy and density functional theory (DFT) to explore periodic trends in the heats of nanoparticle-support interactions for late transition metal and metal oxide nanoparticles on layered niobate and silicate supports. Data for Co(OH)2, hydroxyiridate-capped IrOx.nH2O, Ni(OH)2, CuO, and Ag2O nanoparticles were added to previously reported data for Rh(OH)3 grown on nanosheets of TBA0.24H0.76Ca2Nb3O10 and a layered silicate. ITC measurements showed stronger bonding energies in the order Ag < Cu ≈ Ni ≈ Co < Rh < Ir on the niobate support, as expected from trends in M-O bond energies. Nanoparticles with exothermic heats of interaction were stabilized against sintering as revealed by temperature resolved images recorded using transmission electron microscopy. In contrast, ITC measurements showed endothermic interactions of Cu, Ni, and Rh oxide/hydroxide nanoparticles with the silicate and poor resistance to sintering. These trends in interfacial energies were corroborated by DFT calculations using single-atom and four-atom cluster models of surface-bound metal/metal oxide nanoparticles. Density of states and charge density difference calculations reveal that strongly bonded metals (Rh, Ir) transfer d-electron density from the adsorbed cluster to niobium atoms in the support; this mixing is absent in weakly binding metals, such as Ag and Au, and in all metals on the layered silicate support. The large differences between the behavior of nanoparticles on niobate and silicate supports highlight the importance of d-orbital interactions between the nanoparticle and support in controlling the nanoparticles’ stability.

Stabilization of a Metastable Tunnel‐Structured Orthorhombic Phase of VO2 upon Iridium Doping

“…5 nm are observed almost entirely coating the VO 2 nanocrystals (which at this concentration are crystallized in the M 1 phase) as depicted in Figure f. The dispersion of nanocrystalline Ir metal on the VO 2 surfaces is suggestive of strong interfacial interactions and likely derives from d‐acid/base interactions as originally suggested by Brewer wherein early (V) and late (Ir) transition metals undergo strong orbital mixing of d‐states yielding homogeneously dispersed clusters on the oxide surface …”

Design of Ceria Catalysts for Low‐Temperature CO Oxidation

“…Campbell et al. demonstrated that the oxide formation energy of the metal adatom can be used to predict the adsorption energy of support oxides, and the tendency has been validated experimentally and theoretically . Besides, the metal atom adsorption also depends on the capability of the support oxide to accept electrons to release oxygen atoms, calculated as reduction energy, O'Connor et al.…”

Direct Hydrothermal Synthesis of Size-Controlled Co₃O₄ Nanocubes under Highly Condensed Conditions

“…[1][2][3][4][5] Especially, tricobalt tetraoxide (Co 3 O 4 ), a mixed-valence transition metal oxide with spinel crystal structure, is regarded as one of the most promising p-type semiconducting materials for industrial and scienti c applications such as heterogeneous catalysts, [6][7][8][9][10][11][12] solid-state sensors, [13][14][15] magnetic materials, 16,17) and lithium ion rechargeable batteries. [18][19][20][21] Up to date, various types of preparation methods have been developed for the preparation of Co 3 O 4 by thermal decomposition, [6][7][8]20,22,23) chemical spray pyrolysis, 24) spattering, 25) and sol-gel process.…”