Catalisadores à base de cobre e cobre/paládio suportados em óxido de grafeno reduzido: síntese, caracterização e aplicação na reação de redução de NO por CO

Abstract

In this work, reduced graphene oxide (RGO) was obtained from the oxidation of graphite by the improved Hummers method without addition of sodium nitrate, with subsequent expansion and reduction using thermal methods. The OGR was synthesized to act as support of metals (copper and palladium). The catalysts were synthesized using the wetness impregnation method. The support and catalysts were extensively characterized employing several techniques: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption-desorption, atomic force microscopy (AFM), thermogravimetric analysis (ATG), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR), in situ XRD, and scanning (SEM), transmission (TEM) and scanning transmission (STEM) electron microscopy. The results showed that the graphite oxidation and its subsequent expansion and reduction were efficient, since the RGO obtained showed a high specific area (439 m²/g) and low thicknesses, ranging from mono to few layers. Moreover, the metals were evenly distributed on the surface of the RGO, occurring the formation of the CuO, Cu2O, metallic Pd, PdOx<1, PdO and PdO2 species. The catalysts were evaluated in the reduction reaction of NO using CO as the reducing agent. The catalytic evaluation showed that the reduced catalysts presented better performance, with NO conversions and N2 selectivity above 85% at 350 °C.