The interaction between CO and YBa2Cu3Ox as studied by TG/DTA, FTIR, and XPS

Abstract

The interaction of CO with YBa2Cu3Ox (x ∼ 7) has been studied using differential thermal analysis (DTA)/ thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The interaction at temperatures between 400 and 800 K proceeds as CO + O(lattice) = CO2, as shown by the evolved gas analysis and DTA/TG calorimetric measurement. At 800-1200 K a large CO uptake is observed, resulting in the formation of BaCO3, which is characterized by FTIR, and the reduction of Cu(II) and Y(III), as observed by XPS. An apparent activation energy of 16 kcal/mol and a heat of reaction of 60 kcal/mol are estimated for this high-temperature reaction from the DTA/TG studies. These results are compared with those obtained for YBa2Cu3Oy (y ∼ 6) and the composite compounds, CuO, Y2O3, and BaCO3. A detailed mechanism which may explain the higher catalytic activity on YBa2Cu3Ox than on CuO3 is suggested. © 1993 American Chemical Society.