Journal of Catalysis, Vol.381, 508-519, 2020
Oxidation state of Mo affects dissolution and visible-light photocatalytic activity of MoO3 nanostructures
The role of shape, dissolution, and chemical properties of MoO3 nanomaterials with visible light photocatalytic activity are still largely unknown. In the present study, we investigate the photodegradative properties and role of dissolution products under different pH values of three MoO3 nanomaterials with different shapes and chemical properties (nanorods, nanowires, and nanoplates). We show that different morphologies of MoO3 present different solubility behaviors with increasing pH (with the highest solubility occurring at pH 10), and this dissolution depends on the oxidative state and nature of the MoAO bonds, not just the size and morphology of the nanostructures. Nanoparticle dissolution seems to favorably affect the discoloration rate of methylene blue (MB) but not its photocatalytic degradation. It is important to differentiate MB discoloration as opposed to photocatalytic degradation since discoloration involves not only photocatalytic degradation but also adsorption and ion complexation processes. Our experiments for the removal of MB show that the nanorods present the best photocatalytic-based degradation activity, while the nanowires, which present the highest dissolution, decolorize MB the fastest. MoO3 photocatalytic degradation mechanism was investigated via the quantification of nanoparticle-produced reactive oxygen species (ROS) and measurement of MB photocatalytic degradation inhibition due to the presence of ROS scavengers. According to the results, photogenerated holes in the nanomaterial govern the degradative process by allowing production of hydrogen peroxide. This study demonstrates that MoO3 nanostructure chemical and physical properties, as well as nanostructure dissolution process, influence the photocatalytic properties of MoO (3) nanostructures. (C) 2019 Elsevier Inc. All rights reserved.