Formation of H₂O₂ on Au₂₀ and Au₁₉Pd Clusters: Understanding the Structure Effect on the Atomic Level

Abstract

Supported gold nanoparticles are promising catalysts for production of H2O2 from O2 and H2. Size, structure, and palladium doping effects play the key role in activity and selectivity of a gold catalyst. We performed a study of the influence of Au20 and Au19Pd structure features on the main steps of H2O2 formation on the atomic level, using the DFT/PBE approach with relativistic all electron basis set. The top, edge, and facet atoms of the tetrahedral Au20 cluster as well as a palladium atom of Au19Pd located on the top, edge, and facet of a tetrahedron have been considered as active sites of steps involved in H2O2 synthesis. The thermodynamic and kinetic data including Gibbs free energies and the activation Gibbs free energies were calculated for the steps determining the formation of H2O2 (H(s) + OOH(s) = H2O(2(s)), H2O(2(s)) = H2O(2(g))) and for one step decreasing the selectivity (H2O(2(s)) = OH(s) + OH(s)). Gold tends to have low activity and high selectivity in H2O2 synthesis regardless of the structure of active site. Low coordinated palladium atoms promote H2O2 formation as well as its dissociation. Pd on a facet of a cluster facilitates H2O2 production with high activity and selectivity.

Recent Advances in the Direct Synthesis of H2O2

“…[44][45][46][47][48][49][50] However, a major challenge associated with the direct synthesis of H 2 O 2 is related to catalyst selectivity; often catalysts that offer high activity towards the direct synthesis of H 2 O 2 are also active to its degradation via over hydrogenation or decomposition to H 2 O. [47,[51][52][53] The issue of catalyst selectivity can be understood as the formation of H 2 O from H 2 and O 2 is thermodynamically favourable in comparison to the formation of H 2 O 2 as summarized by Equations (1) and (2) Furthermore, the undesired H 2 O 2 decomposition and hydrogenation reactions are also more thermodynamically favourable than the formation of H2O2 as summarized by Equations (3) and (4). [Equations (3) and (4)]:…”

Quantum mechanical studies of full‐shell noble metal nanoclusters in water

“…Understanding the surface properties of NMNCs paves the way for the expansion of green chemistry . For example, electrophilic agents like oxygen molecules prefer to be absorbed on the surface negatively charged atoms . Table illustrates the variation of the Löwdin net atomic charges of full‐shell M x ( x = 1 355 147) NCs.…”

Catalytic mechanism and bonding analyses of Au-Pd single atom alloy (SAA): CO oxidation reaction

“…In recent years, gold based bimetallic nanoalloy catalysts were synthesized by introducing transition metals (Pd, Pt, Ir) to improve the catalytic efficiency [40][41][42][43]. Among them, gold-palladium (Au-Pd) bimetallic NPs were applied as potential catalysts in a wide range of catalytic reactions, such as oxidation of CO [43][44][45], hydrogen peroxide (H 2 O 2 ) synthesis from H 2 and O 2 [44,[46][47][48][49][50][51], hydrocarbon and methanol oxidation [15, [52][53][54][55], vinyl acetate (VA) synthesis [56,57], dehydration of formic acid [58], decomposition of N 2 O [13] and other transformations [59][60][61][62][63][64]. Pd-Cu single atom alloy (SAA) was found to be active for selective hydrogenation of styrene [65], acetylene [65], and phenylacetylene [66] by Flytzani-Stephanopoulos's group.…”