Photoinhibitive Properties of α-MoO 3 on Its Composites with TiO 2 , ZnO, BiOI, AgBr, and Cu 2 O.

Orthorhombic molybdenum trioxide (α-MoO 3 ) is well known as a photocatalyst, adsorbent, and inhibitor during methyl orange photocatalytic degradation via TiO 2 . Therefore, besides the latter, other active photocatalysts, such as AgBr, ZnO, BiOI, and Cu 2 O, were assessed via the degradation of methyl orange and phenol in the presence of α-MoO 3 using UV-A- and visible-light irradiation. Even though α-MoO 3 could be used as a visible-light-driven photocatalyst, our results demonstrated that its presence in the reaction medium strongly inhibits the photocatalytic activity of TiO 2 , BiOI, Cu 2 O, and ZnO, while only the activity AgBr is not affected. Therefore, α-MoO 3 might be an effective and stable inhibitor for photocatalytic processes to evaluate the newly explored photocatalysts. Quenching the photocatalytic reactions can offer information about the reaction mechanism. Moreover, the absence of photocatalytic inhibition suggests that besides photocatalytic processes, parallel reactions take place.