Development of reusable catalysts based on supported ultrathin gold nanowires

ALVAREZ CERIMEDO MARIA SOLEDAD; AYUDE, MARÍA ALEJANDRA; HOPPE, CRISTINA ELENA

Buenos Aires

Congreso; WCCE11 - 11th World Congress of Chemical Engineering; 2023

Ultrathin gold nanowires (NWs), first synthesized by wet chemistry in 2007 by the group of Ravishankar, are intriguing metallic nanostructures with their length exceeding several micrometers and a typical diameter (1.6-1.7 nm) falling below the critical dimension for quantization (2 nm). Despite their unique and promising properties linked to their dimensions and crystalline defective structure, application of these flexible, anisotropic metallic structures in catalysis remains elusive because of their low stability, especially in colloidal dispersions above room temperature. In the last years, the possibility of using different supports to preserve the morphology and properties of these nanowires has arisen as an appealing alternative. Among economical substrates for flexible devices, paper has brought especial attention especially after its successful use in sensing and microfluidics applications. In this work, the possibility of developing economic, flexible, efficient and simple to fabricate platforms, based on ultrathin Au NWs supported on filter paper (FP) was analysed. The performance of these platforms in the reduction of p-nitrophenol (PNP) to p-aminophenol (PAP) by NaBH4 was studied at room temperature. This is considered a model reaction because it involves the use of simple equipment, a single formation product and simple kinetics under excess of reducing agent. As efficiency of metal nanostructures in catalysis varies, not only with the size and shape of the nanostructures but also with their surface coverage, the influence of the removal of oleylamine (used as coating of the NWs) with a NaBH4 excess on their catalytic activity was determined. We have recently demonstrated that NaBH4 may have an additional role as a catalytic "activator" of metal nanostructures, being able to remove a large number of species from the metallic surface of nanoparticles.The catalytic reaction was conducted by using a batch full recycle glass reactor equipped with mechanical stirring. The concentration of PNP was assessed by monitoring the absorbance measured at 400 nm along time. The catalytic activity and stability of 1 cm x 5.5 cm NWs/FP platforms, fabricated by infiltration, was investigated in successive cycles of reaction conducted at a given set of experimental conditions. The as-prepared catalyst showed to be active and stable for at least 8 3h-cycles. The reaction completely stopped when the NWs/FP was taken from the reactor out. The effect of preliminary NaBH4 washes and thermal treatment on the catalytic performance of the platforms was also studied.