Gold–palladium colloids as catalysts for hydrogen peroxide synthesis, degradation and methane oxidation: effect of the PVP stabiliser

Agarwal, Nishtha; McVicker, Rebecca; Althahban, Sultan; Lewis, Richard J.; Morgan, David; Dimitratos, Nikolaos; Kiely, Christopher J.; Hutchings, Graham J.

doi:10.1039/d0cy00915f

Cited by 23 publications

(28 citation statements)

References 46 publications

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“… 18 , 73 − 78 Testing unsupported AuPd nanoparticles ( Table S4 ) highlights the crucial role of both the stabilizer and support in the determination of the catalyst activity through modifications of the metal–support–stabilizer interface. 79 Regardless of the stabilizer used, catalysts prepared with acid (H 2 SO 4 , 133 ppm) are systematically more active, on a metal molar basis, than their homologues prepared in the absence of acid. The same trend is observed for the Au/Pd molar ratio.…”

Section: Resultsmentioning

confidence: 99%

Impact of the Experimental Parameters on Catalytic Activity When Preparing Polymer Protected Bimetallic Nanoparticle Catalysts on Activated Carbon

et al. 2022

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Sol immobilization is used to produce bimetallic catalysts with higher activity to monometallic counterparts for a wide range of environmental and commercial catalytic transformations. Analysis of complementary surface characterization (XPS, Boehm’s titration, and zeta potential measurements) was used to elucidate alterations in the surface functionality of two activated carbon supports during acid exposure. When considered in parallel to the experimentally determined electrostatic and conformational changes of the polymer surrounding the nanoparticles, an electrostatic model is proposed describing polymer protected nanoparticle deposition with several polymer–carbon support examples described. Consideration of the electrostatic interactions ensures full deposition of the polymer protected nanoparticles and at the same time influences the structure of the bimetallic nanoparticle immobilized on the support. The normalized activity of AuPd catalysts prepared with 133 ppm H 2 SO 4 has a much higher activity for the direct synthesis of hydrogen peroxide compared to catalysts prepared in the absence of acid. Detailed characterization by XPS indicates that the surface becomes enriched in Au in the Au–Pd samples prepared with acid, suggesting an improved dispersion of smaller bimetallic nanoparticles, rich in Au, that are known to be highly active for the direct synthesis reaction. Subsequent microscopy measurements confirmed this hypothesis, with the acid addition catalysts having a mean particle size ∼2 nm smaller than the zero acid counterparts. The addition of acid did not result in a morphology change, and random alloyed bimetallic AuPd nanoparticles were observed in catalysts prepared by sol immobilization in the presence and absence of acid. This work shows that the deposition of polymer protected AuPd nanoparticles onto activated carbon is heavily influenced by the acid addition step in the sol immobilization process. The physicochemical properties of both the polymer and the activated carbon support should be considered when designing a bimetallic nanoparticle catalyst by sol immobilization to ensure the optimum performance of the final catalyst.

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Section: Resultsmentioning

confidence: 99%

Impact of the Experimental Parameters on Catalytic Activity When Preparing Polymer Protected Bimetallic Nanoparticle Catalysts on Activated Carbon

et al. 2022

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“…The catalytic performance of a series of Au/AC_ PVA and Au/AC_PVP supported nanoparticles were investigated for the HDO oxidation to adipic acid by varying the stabilizer to Au weight ratio on the synthesised Au colloidal nanoparticles. In previous studies [21,23], we have shown the importance of tuning the amount of stabilizer for controlling not only the morphological properties of the supported metal nanoparticles but also to influence the activity, the selectivity to desired products and the catalytic stability. A high-pressure batch reactor was firstly used for the initial catalytic screening of the synthesized catalysts at reaction conditions that have been reported in our previous work [41].…”

Section: Characterization Of the Catalystsmentioning

confidence: 99%

“…Two different stabilizers were used: poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP). The effect of the stabilizer to Au weight ratio was studied as it is known that has influence in: (i) controlling particle size of the metal and (ii) affecting dispersion of the preformed metal nanoparticles on the support and finally influencing catalytic activity due to the amount of the polymer presented on the surface of the catalyst [21][22][23][24][25][26][27][28][29][30]. Moreover, reaction parameters such as stirring rate, time, temperature, substrate to NaOH ratio were studied.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Colloidal Preparation Method for Supported Preformed Colloidal Au Nanoparticles for the Liquid Phase Oxidation of 1,6-Hexanediol to Adipic Acid

et al. 2022

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Supported on activated carbon gold colloidal nanoparticles have been prepared in the presence of the stabilizing polymer PVA and PVP (polyvinylalcohol, polyvinylpyrrolidone). The effect of the polymer to the Au weight ratio was investigated, for synthesizing gold nanoparticles with different particle size and particle size distribution. By varying the polymer/Au wt/wt ratio, gold nanoparticles with mean diameters from 3 to 8 nm were synthesized. The synthesized Au catalysts were studied in the liquid phase oxidation of 1,6-hexanediol (HDO) to adipic acid under base and base-free conditions. A range of experimental parameters were varied for the optimization of reaction conditions and the most promising Au catalysts were further evaluated in terms of catalytic performance. We demonstrated that the influence of choice of polymer, tuning the polymer to Au weight ratio, HDO to Au molar ratio, and use of basic conditions have an important influence in terms of catalytic activity and selectivity to adipic acid. The highest yield to adipic acid was obtained using Au-PVA catalysts (40% at 110 °C under base free conditions), however, at low HDO to Au molar ratio and lower carbon balance (70–80%). On the contrary, at higher HDO to Au molar ratio, and under basic conditions, the yield was in the range of 18–20% with a significant improvement in terms of carbon balance (88–100%).

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“…For any heterogeneous catalyst operating in a three-phase system the possibility of the leaching of the active phase and resulting homogeneous contribution to observed catalytic performance is of great concern, with the activity of homogeneous Fe and Pd species known to catalyse the formation of oxygen-based radicals (via Fenton's pathways) and the direct synthesis of H 2 O 2 respectively. [49][50][51][52][53] Analysis of post reaction solutions via MP-AES (Table S.6 †) reveals minimal leaching of Pd in the post-reaction solution. On the other hand, a significant amount of leached Fe is observed, regardless of catalyst composition.…”

Section: Catalysis Science and Technology Papermentioning

confidence: 99%

The degradation of phenol via in situ H₂O₂ production over supported Pd-based catalysts

Santos

Lewis

Morgan

et al. 2021

Catal. Sci. Technol.

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Gold–palladium colloids as catalysts for hydrogen peroxide synthesis, degradation and methane oxidation: effect of the PVP stabiliser

Abstract: PVP polymer stabilisers effect the reactivity of AuPd nanoparticles towards H2O2 synthesis/decomposition and methane oxidation.

Cited by 23 publications

References 46 publications

Impact of the Experimental Parameters on Catalytic Activity When Preparing Polymer Protected Bimetallic Nanoparticle Catalysts on Activated Carbon

Impact of the Experimental Parameters on Catalytic Activity When Preparing Polymer Protected Bimetallic Nanoparticle Catalysts on Activated Carbon

Effect of the Colloidal Preparation Method for Supported Preformed Colloidal Au Nanoparticles for the Liquid Phase Oxidation of 1,6-Hexanediol to Adipic Acid

The degradation of phenol via in situ H₂O₂ production over supported Pd-based catalysts

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Gold–palladium colloids as catalysts for hydrogen peroxide synthesis, degradation and methane oxidation: effect of the PVP stabiliser

Abstract: PVP polymer stabilisers effect the reactivity of AuPd nanoparticles towards H2O2 synthesis/decomposition and methane oxidation.

Cited by 23 publications

References 46 publications

Impact of the Experimental Parameters on Catalytic Activity When Preparing Polymer Protected Bimetallic Nanoparticle Catalysts on Activated Carbon

Impact of the Experimental Parameters on Catalytic Activity When Preparing Polymer Protected Bimetallic Nanoparticle Catalysts on Activated Carbon

Effect of the Colloidal Preparation Method for Supported Preformed Colloidal Au Nanoparticles for the Liquid Phase Oxidation of 1,6-Hexanediol to Adipic Acid

The degradation of phenol via in situ H2O2 production over supported Pd-based catalysts

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The degradation of phenol via in situ H₂O₂ production over supported Pd-based catalysts