Potassium surface stability and electronic promotion in K-NbN0.9O0.1 catalysts

Potassium promoted niobium oxynitride catalysts were investigated by specie s resolved thermal alkali desorption (SR-TAD) method, Energetic barriers fo r potassium ions and atoms desorbing from the catalyst surface were determi ned. They are in the range of 1.0-2.3 and 2.3-3.0 eV for K and K+, respecti vely, depending on the way of the promoter introduction (via nascent- or po st-doping). The work function (3.0-3.8 eV) was evaluated from the Schottky energy cycle. The shifts of the Fermi edge upon K doping were confirmed by parallel XPS studies. The surface stability of the promoter and its electro nic action were found to be inimical. The lowering of the work function was greater for the post-doped sample, but the stability of potassium was dist inctly lower than that observed in the case of the nascent one. (C) 2000 El sevier Science B.V. All rights reserved.