Supported metal nanoparticles for sustainable green catalytic processes

Preformed Au nanoparticles supported on activated carbon and TiO2 were synthesised by sol-immobilisation. Polyethylene glycol, polyvinyl pyrrolidone and polyvinyl alcohol were used as stabilisers for the gold nanoparticles at different polymer/Au wt/wt ratios for each polymer. The effect of polymer/Au wt/wt ratios was investigated on (i) the average nanoparticle size, (ii) catalytic activity for two reactions, 4-nitrophenol reduction and glucose oxidation to glucaric acid. 4-nitrophenol reduction is recognised as a model reaction for nanomaterial catalytic activity tests; glucose oxidation to glucaric acid is a reaction that is traditionally carried out with concentrated nitric acid, for which alternative reaction pathways are looked for in an effort to reduce its environmental impact. The catalysts were characterised from the nanoparticle synthesis by colloidal method by means of UV-vis spectroscopy and DLS analysis, to the immobilisation step by XRD and TEM. The effect of the polymer:Au wt/wt ratio on nanoparticle size depends on the polymer nature, and point out the need to optimise supported nanoparticle synthesis protocols in the future depending on the type of stabiliser. The catalytic tests revealed that the polymers interact with Au nanoparticles through different active sites. Activated carbon (AC) and TiO2 were compared as supports for Au nanoparticles stabilised by PVA at PVA/Au 0,65 wt/wt. AC-supported Au NPs were the most active for glucose oxidation while TiO2-stabilised Au NPs were five times more active in 4-nitrophenol reduction that AC-supported NPs. Hence support and stabiliser are important parameters that should be optimised in order to achieve high catalytic activity for a given reaction.

Synthesis and characterisation of electrospun gold on ceria catalysts

Cerium oxide in catalysis can be used both as support and as a catalyst itself. Ceria catalyses many oxidations reactions, its excellent catalytic properties are due to its store oxygen storage capacity (OSC) and the reticular defects present on its surface. Different morphologies expose different reticular planes, and different reticular planes can expose different amounts of defects. The preparation method of cerium oxide can influence the surface area, morphology, and the number of defects in the sample. This work is focused on different preparation methods for gold nanoparticles supported on 1D nanostructures of cerium oxide prepared via electrospinning, their XRD, DRUV-Vis and Raman characterizations, and their catalytic performance on the oxidation reaction of HMF to FDCA.