TPR and XPS investigations of Co/Al2O3 catalysts promoted with Ru, Ir and Pt

The influence of small amount of noble metals (Ru, Ir and Pt) on the reduction of Co atoms in supported Co catalysts has been investigated by TPR and XPS measurements. The catalysts, containing 8 at% Co and different amounts of promoting metals (less than or equal to1 at%) such as Pt, Ir or Ru, were prepared by sequential impregnation. The change in Co reducibility was investigated by XPS to quantify the surface reduction degree of cobalt and by TPR to demonstrate that the presence of the second metal strongly influences the reducibility of the catalysts with TPR shifting to lower temperatures. The efficiency in Co reduction was Ir > Pi > Ru, both at low and high promoter amount, while a complete Co reduction was never found in our operative conditions.