Abstract: The redox behavior of Ag-doped bismuth vanadomolybdate catalysts and promotion of catalysis by Ag⁺ have been investigated by XPS in situ Ar⁺ ion etching. The results of XPS show that Mo⁶⁺ cation is the site on which hydrocarbons absorb and Bi³⁺ cation is responsible for converting molecular oxygen into lattice oxide ion. In the reaction process. Mo⁶⁺ cation is reduced by hydrocarbons and Bi³⁺ cation is oxidized by molecular oxygen. The V⁵⁺ cation is involved in diffusing O^2- and transferring electrons into the bulk of catalysts. Ag⁺-promoter is conducive to forming lattice oxide ions frorn molecular oxygen and increasing the reoxidation speed on the position of Bi^3- cation.

Key words: bismuth vanadomolybdate, Ag⁺-promoter, XPS spectra, Ar⁺ ion etching, redox behavior