In-Situ Deposition of Plasmonic Gold Nanotriangles and Nanoprisms onto Layered Hydroxides for Full-Range Photocatalytic Response towards the Selective Reduction of p-Nitrophenol

Abstract

In this work, we present photocatalysis as a greener alternative to conventional catalysis where harsh reaction conditions, temperature and/or pressure are needed. Photodegradation of organic pollutants is a cost-effective, eco-friendly solution for the decontamination of water and air, and is a field that has been continuously growing over the last decade. Plasmonic metal nanoparticles absorb light irradiation that is transferred to the chemical reaction in a different fashion. Furthermore, plasmonic nanostructures can be combined with other materials, such as semiconductors or a basic support, to create hybrid systems capable of overcoming certain challenges that photocatalysis is facing nowadays and to expand the photocatalytic response towards the whole visible-near infrared (Vis-NIR) ranges. The main objective of this work has been to in-situ synthesize plasmonic anisotropic gold nanoparticles onto hydrotalcite (HT) and calcined hydrotalcite (CHT) supports by way of a sequential deposition-reduction (DR) process and to evaluate their efficiency as heterogeneous catalysts towards the selective oxidation of p-nitrophenol (hereafter 4-NP), a well-known model contaminant, either in the absence or the presence of full-range light irradiation sources (LEDs) spanning the whole UV-Vis-NIR range. Special attention has been paid to the optimization of the catalyst preparation parameters, including the pH and the concentration of reducing and stabilizing agents. Interestingly, the use of thermally modified hydrotalcites has enabled a strong metal-support interaction to induce the preferential formation of triangular-shaped Au nanoparticles with ca. 0.8 wt.% loading while increasing the colloidal stability and surface area of the catalyst with respect to the commercial untreated HT supports.

Triangular and Prism‐Shaped Gold‐Zinc Oxide Plasmonic Nanostructures: In situ Reduction, Assembly, and Full‐Range Photocatalytic Performance

“…Previous studies have suggested the strong influence of pH as a key control parameter to increase the yield of anisotropic gold nanostructures , . This influence has been further confirmed and extended in this study that enabled us to generate triangular‐shape Au structures despite of using ZnO instead of an accommodating support with a more basic nature (i.e.…”

“…This influence has been further confirmed and extended in this study that enabled us to generate triangular‐shape Au structures despite of using ZnO instead of an accommodating support with a more basic nature (i.e. hydrotalcites) , . In addition, a control experiment carried out at neutral pH rendered the preferential formation of pseudo‐spherical Au NPs (see Figure S3), thereby confirming the influence of basic pH to favor the preferential growth of gold anisotropic shapes.…”

“…The synthesis of the Au‐ZnO consisted in an in‐situ reduction‐deposition method that included the use of sodium citrate as ligand stabilizer, sodium borohydride as reducing agent and sodium hydroxide to promote a highly alkaline reaction conditions (pH ca. 12.5).…”

“…12.5). This basic ambient with a high concentration of hydroxyl groups has been previously demonstrated to favor the preferential formation of anisotropic gold nanostructures , . A simplified overview of the synthesis approach is displayed below (Figure , specific experimental details are described in the Experimental Section).…”

Catalytic transfer hydrogenation of furfural into furfuryl alcohol over Ni–Fe‐layered double hydroxide catalysts

“…A broad absorption band at around 3,460 cm −1 was attributed to the stretching vibration of the –OH groups. The band at 1,625 cm −1 was assigned to the bending motion of interlayer water . The absorption bands appearing at 1,363 cm −1 and 834 cm −1 were assignable to the asymmetric stretching mode and out‐of‐plane deformation vibration of interlayer carbonate species .…”