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.I nt his work, an oxygen dimer structure was observed and identified on gold nanoparticles in catalytic decomposition of hydrogen peroxidetooxygen and water.This structure,which is different from isolated atomic or molecular oxygen surface structures,w as observed with in situ surfaceenhanced Raman spectroscopic measurements and identified with density functional theory calculations.T he 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 showthat on surfaces with coordinatively unsaturated gold atoms,two oxygen atoms preferentially share agold atom with abond distance of 0.194-0.196 nm and additionally bind to two other surface gold atoms with al arger bond distance of 0.203-0.213 nm, forming an Au-O-Au-O-Au structure.T he formation of this structure depends on reaction rates and conditions.

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

“…The remaining two bottom layers were constrained at the bulk Ni positions, accounting for the bulk structure. Similarly constructed periodic surfaces with similar computational settings were previously used successfully for studying adsorption and reactions on Ni [13] and other metal surfaces [14–23] …”

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.…”

“…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. The O-O bond distance gradually increases, and its stretching vibration, n(O-O), accordingly, progressively decreases from 1185 cm À1 for a bulk Au surface to 1049 cm À1 for a subnanometer-size Au cluster.…”

“…The O-O bond distance gradually increases, and its stretching vibration, n(O-O), accordingly, progressively decreases from 1185 cm À1 for a bulk Au surface to 1049 cm À1 for a subnanometer-size Au cluster. 7,8 Similarly for atomic oxygen, as an O atom becomes more strongly bound to smaller Au particles, its O-Au distances progressively decrease and, accordingly, n(O-Au) increases from 373 to 467 cm À1 . 7,8 As another example, for dissociative H 2 adsorption, the Au-H bond becomes progressively stronger with decreasing Au particle size.…”

“…7,8 Similarly for atomic oxygen, as an O atom becomes more strongly bound to smaller Au particles, its O-Au distances progressively decrease and, accordingly, n(O-Au) increases from 373 to 467 cm À1 . 7,8 As another example, for dissociative H 2 adsorption, the Au-H bond becomes progressively stronger with decreasing Au particle size. 9 In this work, DRIFTS experimental measurements with Au particles of different sizes and density functional theory (DFT) calculations for Au surfaces ranging from subnanometer clusters to bulk Au show that in contrast with oxygen and other adsorbate structures that are highly sensitive to the Au particle size, hydroxyls are structure insensitive.…”