Copper oxide catalyst supported on niobium oxide for CO oxidation at low temperatures

CuO/Nb2O5 shows higher CO oxidation activity than CuOx/Al2O3. Analysis of X-ray photoelectron spectra shows the presence of Cu1+ species on Nb2O5, which is known to be the active species for CO oxidation. In contrast, only Cu2+ is found to be present on Al2O3. Enhanced activity of CuOx/Nb2O5 is consistent with its lower activation energy for CO oxidation compared with CuOx/Al2O3. It is argued that the formation of stable Cu1+ species on Nb2O5 is a result of presence of deep copper acceptor states within the band gap of Nb2O5. 6%CuOx/Nb2O5 shows comparable activity to 1%Pt/Al2O3 but loses its advantage above 500 degrees C.