One-Step Synthesis of AuCu/TiO₂ Catalysts for CO Preferential Oxidation

Abstract

Au/TiO₂ (1wt% Au), Cu/TiO₂ (1wt% Cu) and AuCu/TiO₂ (1wt% AuCu) catalysts with different Au:Cu mass ratios were prepared in one-step synthesis using sodium borohydride as reducing agent. The resulting catalysts were characterized by X-ray diffraction (XRD), X-ray Dispersive Energy (EDX), Transmission Electron Microscopy (TEM) and Temperature Programmed Reduction (TPR) and tested for the preferential oxidation of carbon monoxide (CO-PROX reaction) in H₂-rich gases. EDS analysis showed that the Au contents are close to the nominal values whereas for Cu these values are always lower. X-ray diffractograms showed only the peaks of TiO₂ phase; no peaks of metallic Au and Cu species or oxides phases were observed. TPR and high-resolution TEM analysis showed that AuCu/TiO₂ catalysts exhibited most of Au in the metallic form with particles sizes in the range of 3-5 nm and that Cu was found in the form of oxide in close contact with the Au nanoparticles and well spread over the TiO₂ surface. The AuCu/TiO₂ catalysts exhibited good performance in the range of 75-100 °C and presented a better catalytic activity when compared to the monometallic ones. A maximum CO conversion of 98.4% with a CO₂ selectivity of 47% was obtained for Au_0.50Cu_0.50/TiO₂ catalyst at 100^oC.

Keywords:
AuCu/TiO₂ catalyst; carbon monoxide; preferential oxidation; hydrogen