Brønsted–Evans–Polanyi Relations for H2O2 Synthesis on Gold Surfaces

Abstract

By means of density functional theory calculations, the reaction mechanisms of H 2 O 2 synthesis on three low index and two stepped Au surfaces have been investigated in detail. This study shows the activation energies of five elementary reaction steps of H 2 O 2 synthesis, which include two hydrogenation and three decomposition steps of key species, are a function of reaction energies, which observe the Brønsted-EvansPolanyi rules on both the flat Au surfaces and the step edge sites of stepped Au surfaces. This study not only provides a simple method to estimate the reaction barriers of elementary steps of H 2 O 2 synthesis by the reaction energies but also predicts the catalytic performances of Au nanoparticles applied in real catalysis.

The effect of CNTs on structures and catalytic properties of AuPd clusters for H2O2 synthesis

“…The main elementary reactions of H 2 O 2 formation by the hydrogenation of molecular oxygen are the following: hydrogenation reactions on the Pd ensemble of Au 5 Pd 5 /CNTs are slightly smaller than those on Pd(111) surfaces (0.75 and 1.13 eV respectively) reported by Meyer, 19 but similar to those on the bare AuPd icosahedral cluster with 55 atoms (0.72 and 0.62 eV respectively) reported by Hwang et al 21 For the transition state of the first hydrogenation step (OOH) on two kinds of reaction sites, as shown in Fig. 6c, the bond lengths between oxygen and hydrogen are very close and similar to the results reported by Wang et al 24 on Pd 1 Au(110) and Pd 1 Au(100). However, the transition state of the second hydrogenation step (H 2 O 2 ) and the bond length are very different on AuPd (2.467 A ˚) and on Pd ensembles (1.627 A ˚)…”

“…22 The study of Yoshizawa et al 20 shows that the less active Au atoms on the bare AuPd catalysts play a main role in increasing the barrier for the dissociation of H 2 O 2 . Our recent study 24 of H 2 O 2 synthesis on single Pd decorated Au surfaces shows that the activation energies of five elementary reaction steps of H 2 O 2 synthesis are a function of reaction energies, which observe the Brønsted-Evans-Polanyi rules on both the flat Au surfaces and the step edge sites of stepped Au surfaces. It can be seen that most of the theoretical studies 16,[19][20][21][22][23][24] have been conducted to investigate the role of Au in catalytic properties of bimetallic AuPd for H 2 O 2 synthesis.…”

“…Our recent study 24 of H 2 O 2 synthesis on single Pd decorated Au surfaces shows that the activation energies of five elementary reaction steps of H 2 O 2 synthesis are a function of reaction energies, which observe the Brønsted-Evans-Polanyi rules on both the flat Au surfaces and the step edge sites of stepped Au surfaces. It can be seen that most of the theoretical studies 16,[19][20][21][22][23][24] have been conducted to investigate the role of Au in catalytic properties of bimetallic AuPd for H 2 O 2 synthesis. In addition, we also noted that compared with a number of theoretical studies of adhesion and catalytic properties of Au, Pd and AuPd nanoclusters on metal oxide supports, [27][28][29] few studies of these clusters on carbon material supports, including carbon nanotubes, have been reported.…”

“…1 The direct synthesis of H 2 O 2 from molecular hydrogen and oxygen, as an environmentally friendly process, will certainly play an increasingly important role in green chemical synthesis in which the formed H 2 O 2 is directly applied in an oxidation reaction. Therefore, a lot of experimental [3][4][5][6][7][8][9][10][11][12][13][14][15] and theoretical studies [16][17][18][19][20][21][22][23][24][25][26] have been conducted on the direct synthesis of H 2 O 2 from molecular hydrogen and oxygen. Pd is the most widely investigated and highly efficient catalyst in the direct synthesis of H 2 O 2 .…”

“…There are several theoretical studies [16][17][18][19][20][21][22][23][24][25][26] of H 2 O 2 synthesis on low-index Pd, Au, Pt surfaces or small Au clusters. The study by Meyer and Todorovic shows that the step which governs the non-selective formation of water during the direct synthesis of H 2 O 2 shifts from O 2 dissociation to OOH dissociation to H 2 O 2 decomposition upon changing the surface from Pd to Pt to Au.…”