CeO2/CuOx nanostructured films for the oxidation of CO using a micro-reactor

ANA PAULA CABELLO; ROCÍO PAPURELLO; MARÍA ALICIA ULLA; JUAN MANUEL ZAMARO

Santa Fe

Conferencia; VI San Luis Conference; 2018

INTEC-UNL-CONICET

Copper oxides have catalytic activity in numerous oxidation reactions and in recent years the attention has been focused on the study of catalysts based on these phases, due to their lower cost compared to other formulations based on noble metals. In addition, the catalytic performance of these oxides can be maximized if they are arranged on the surface of micro-reactors1. For this reason, it is interesting to synthesize CuOx nanostructures in substrates that can be used in these applications. An alternative is the in-situ growth of CuOx on copper substrates, by oxidation treatments. Recent studies have reported the oxidation of Cu substrates by direct heating in air2,3 or by using vapors of ammonia and H2O24. Both methods can generate CuOx nanostructures on the surface of the substrate that give rise to the formation of nanometric interstices. In this context, the aim of this work is to synthesize CuOx nanostructured films on copper foils with micro-channels and then modify them with CeO2 nanoparticles as a promoter. Subsequently, these systems were tested in a micro-reactor using the catalytic oxidation of CO as a test reaction.CuOx nanostructures were synthesized on copper substrates by heat treatments in muffle (CAL method) (2 °C/min, 500 °C, 8h) and by treatments with ammonia and H2O2 vapors (VAP method) (80 °C, 8h), being these methods previously optimized by our group for flat substrates5.Subsequently, on the CAL samples, CeO2 nanoparticles from colloidal ceria suspensions were included onto the CuOx film. By XRD and SEM it was determined that the samples obtained by CAL showed a development of CuOx nano-needles (length 11 µm, width 330 nm) that covered uniformly and densely the micro-channels. In the VAP samples, XRD and SEM showed an homogenous CuOx layer with well-packed nano-wires morphology (1 μm long and 150 nm width). Mechanical stability tests were carried out by ultrasound in water and in acetone, and showed a good adhesion of the films oxide with an initial mass loss that then reaches a stabilization in time, the films generated by the VAP method being of greater stability than those obtained by CAL. After the impregnation of the CAL samples with ceria suspensions, an anchoring of the nanoparticles in the CuOx structures was obtained. By TGA and SDTA it was determined that the optimum temperature of total elimination of the stabilizer of the nanoparticles in air is about 400 °C. After calcination of the CeO2/CuOx (CAL) samples in air at 400 °C for 1 h, the SEM images show that the nano-needles were covered by a thin layer of well anchored CeO2 nanoparticles that completely covered all the surface.The catalytic activity for the CO oxidation of these films was evaluated through a micro-reactor. The nanostructured CuOx films obtained by CAL presented a good performance (T50=190 °C) and its activity was significantly boosted by the incorporation of CeO2 nanoparticles (T50 = 125 °C). In addition the micro-reactor supporting the inverse catalytic phase of CeO2/CuOx, did not show deactivation under reaction atmosphere for 25h at high conversions levels.