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

Abstract

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.

Valorization of Plastic Wastes for the Development of Adsorbent Designed for the Removal of Emerging Contaminants in Wastewater

“…Catalyst design is crucial to regulate the creation of CNTs [90]. The composition, pretreatment conditions, preparation procedures, interactions with support, and shape of catalysts all significantly impact their stability, activity, and selectivity [91,92]. The synthesis of high yields of CNTs that are of excellent quality, a very stable and active catalyst, is a prerequisite [93].…”

Cyclohexanone ammoximation via in situ H2O2 production using TS-1 supported catalysts

“…Mono-, bi-and tri-metallic 0.66%AuPdPt/TiO 2 catalysts have been prepared (on a weight basis) by a sol-immobilisation procedure, based on a methodology previously reported in the literature, 22 which has been shown to result in enhanced precious metal dispersion by limiting particle growth, while also allowing for improved interaction between active metal components. 23,26 The procedure to produce the 0.275%Au-0.275%Pd-0.11%Pt/TS-1 catalyst (2 g) is outlined below with a similar methodology utilised for all catalysts.…”

“…Typically colloidal approaches involve the rapid chemical reduction of metal precursor species and the inhibition of particle agglomeration through the use of capping agents, with the application of such species, often reported to result in the modification of catalyst reactivity through steric effects and modification of metal oxidation states. [23][24][25] With this in mind and in an attempt to better utilise precious metal sites and further improve on the rate of cyclohexanone ammoximation we have recently reported, within this current study we have evaluated the efficacy of TS-1 immobilised AuPd nanoparticles, synthesised by a facile sol-immobilisation technique, 26 towards the in situ ammoximation of cyclohexanone to the corresponding oxime.…”

“…With this in mind and in an attempt to better utilise precious metal sites and further improve on the rate of cyclohexanone ammoximation we have recently reported, within this current study we have evaluated the efficacy of TS-1 immobilised AuPd nanoparticles, synthesised by a facile sol-immobilisation technique, 26 towards the in situ ammoximation of cyclohexanone to the corresponding oxime.…”

Construction of Enriched Metal Vacancies to Enhance Catalytic Behavior for Selective Hydrogenation Over Au–Cu Nanoalloys

“…Gold as a latent green catalyst has been found to be selective for the hydrogenation of some unsaturated groups, such as CO and CC, owing to its unique nature to desorb olefins at lower temperatures than alkynes. , In the past few decades, much effort has been devoted to the development of novel Au catalysts, including the modification of Au particle size, the introduction of second metals, or the selection of the suitable supports. , It was found that an approximately full selectivity was achieved for Au nanoparticles of 2.5–3 nm since the deviation from the spherical shape of the metal particle contributes to the increase of the highly efficient corners and edges . Recently, some strategies have been developed to engineer metal surfaces to adjust the energy of intermediate binding, , in which the construction of metal atomic vacancies affected catalytic behavior by tuning the electronic state of neighboring atoms and thus the energy barriers of the rate-limiting reaction intermediates. , For instance, Zhuang et al found that by structuring surface Cu vacancies, *C 2 H 3 O intermediates made it easier to produce C2 products.…”