Photocatalyst M_1/3NbMoO₆ (M = Fe, Ce) was prepared by the ion-exchange of LiNbMoO₆ with M(NO₃)₃. The structure and spectral response of the as-prepared samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and UV-vis diffuse reflectance spectroscopy (UV-via DRS). Photocatalytic performance was evaluated by oxidation of ethyl mercaptan (EM) under visible and UV light irradiation. Results reveal that a significant interaction existed between the terminal MoO bond in the MoO₆ octahedral unit in the laminate structure and the interlayer cations. The magnitude and mode of this interaction depend on the interlayer cation, including its position, Coulomb field and electrical configuration. The microstructure, spectral response features and photocatalytic oxidation performance are also directly affected by the factors discussed above.