Observation and Identification of an Atomic Oxygen Structure on Catalytic Gold Nanoparticles

Abstract

Interactions between oxygen and gold surfaces are fundamentally important in diverse areas of science and technology. In this work, an oxygen dimer structure was observed and identified on gold nanoparticles in catalytic decomposition of hydrogen peroxide to oxygen and water. This structure, which is different from isolated atomic or molecular oxygen surface structures, was observed with in situ surface-enhanced Raman spectroscopic measurements and identified with density functional theory calculations. The experimental measurements were performed using monodisperse 5, 50 and 400 nm gold particles supported on silica with liquid-phase hydrogen and deuterium peroxides at multiple pH values. The calculations show that on surfaces with coordinatively unsaturated gold atoms, two oxygen atoms preferentially share a gold atom with a bond distance of 0.194-0.196 nm and additionally bind to two other surface gold atoms with a larger bond distance of 0.203-0.213 nm, forming an Au-O-Au-O-Au structure. The formation of this structure depends on reaction rates and conditions.

Propane Dehydrogenation to Propylene and Propylene Adsorption on Ni and Ni‐Sn Catalysts

“…Similarly constructed periodic surfaces with similar computational settings were previously used successfully for studying adsorption and reactions on Ni [13] and other metal surfaces. [14][15][16][17][18][19][20][21][22][23] Adsorption energies were calculated at 0 K without zero-point energy corrections using as a reference the sum of energies for the corresponding clean surface and an isolated propylene molecule calculated separately. Adsorption energies are reported as positive numbers, À ΔE ads .…”

Band gap of reduced graphene oxide tuned by controlling functional groups

“…The density of states was calculated with 1 empty band and a k-point grid of 2 Â 2 Â 1.The computational settings were similar to those that were previously used successfully to describe molecular properties of surface functional groups, including hydroxyls. [54][55][56][57][58] The rGO structure was modeled as an infinite slab constructed using a periodic unit cell. Edge sites were not considered in the model because they represented less than 0.2% of all carbon atoms due to the large size of our rGO sheets (300-800 nm).…”

Spectroscopic observation and structure-insensitivity of hydroxyls on gold

“…As an example, our study with monodisperse 5, 50 and 400 nm Au particles showed that the rate of catalytic H 2 O 2 decomposition increased dramatically with decreasing Au particle size when the total number of surface Au atoms was kept constant. 7,8 For adsorbates, experimental and computational studies demonstrate that adsorption energies and, consequently, geometries and vibrational frequencies of atomic and molecular oxygen on Au surfaces are highly dependent on the size of Au particles. [7][8][9] As an example, while molecular oxygen on Au(111) is unstable, its adsorption becomes progressively more energetically favorable with decreasing Au particle size.…”