The Direct Synthesis of Hydrogen Peroxide over AuPd Nanoparticles: An Investigation into Metal Loading

Joseph Brehm,Richard J Lewis,Graham J Hutchings,Thomas E Davies,David J Morgan

doi:10.1007/s10562-021-03632-6

Joseph Brehm, Richard J Lewis + Show 3 more

Open Access

https://doi.org/10.1007/s10562-021-03632-6

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Journal: Catalysis Letters	Publication Date: Apr 20, 2021
Citations: 16	License type: open-access

Affiliation: Cardiff University, Research Complex at Harwell

Abstract

The direct synthesis of H2O2 from molecular H2 and O2 over AuPd catalysts, supported on TiO2 and prepared via an excess chloride co-impregnation procedure is investigated. The role of Au:Pd ratio on the catalytic activity towards H2O2 formation and its subsequent degradation is evaluated under conditions that have previously been found to be optimal for the formation of H2O2. The combination of relatively small nanoparticles, of mixed Pd-oxidation state is shown to correlate with enhanced catalytic performance. Subsequently, a detailed study of catalytic activity towards H2O2 synthesis as a function of AuPd loading was conducted, with a direct correlation between catalytic activity and metal loading observed.Graphic

Highlights

Hydrogen peroxide (H2O2) is a powerful, environmentally friendly oxidant with an active oxygen content second only to molecular oxygen
In keeping with numerous previous works [29, 36], our initial studies established the ability of Au incorporation into a supported Pd catalyst to significantly improve catalytic performance towards H 2O2 synthesis, with H2O2 formation rates over the 0.5% Au–0.5% Pd/TiO2 catalyst (96 molH2O2 kgcat−1 h−1) far greater than that observed over the analogous Au- (1 molH2O2 kgcat−1 h−1) or Pdonly (26 molH2O2 kgcat−1 h−1) materials (Table 1)
As previously observed for the 0.5% Au–0.5% Pd/TiO2 catalyst exposed to a reductive heat treatment alone, there is a significant loss of surface Cl content upon use in the direct synthesis reaction for all catalysts (Figure S.8) and it is this which we consider to be the fundamental cause for the loss in catalytic performance observed upon reuse

Summary

Introduction

Hydrogen peroxide (H2O2) is a powerful, environmentally friendly oxidant with an active oxygen content second only to molecular oxygen. There are concerns associated with the carbon-efficiency of the AO process, with the over hydrogenation of the anthraquinone carrier molecule necessitating its periodic replacement As such an alternative means to produce H2O2 on-site, at desirable concentrations would have major economic and environmental benefits and to this end the direct synthesis of H2O2 from molecular H 2 and O2, has been extensively studied [1, 3, 7–9]. Several studies have reported that in comparison to Pd-only analogues, AuPd surfaces interact less strongly with H2O2, with the energetic favourability of O–O bond cleavage of Pd surfaces greatly reduced through the introduction of Au [29–31] With these earlier studies in mind and with growing interest in the continual supply of low concentrations of H2O2 to facilitate chemical transformations [32] we investigate the effect of metal loading on the ability of AuPd catalysts on the direct synthesis of H2O2

Catalyst Preparation

Note 2

Results and Discussion

Conclusion