Easily hydroxylated PtxPd1-x-TiO2 nanotube arrays: An energetic Schottky photocatalyst for synergistically boosted degradation of Microcystin-LR

The metal co-catalyst-based photocatalytic oxidation technology provides a promising approach to eliminate contaminants from water. However, the applicability of these catalysts often suffer from severe carrier recombination and high activation energy barriers of reactive oxygen species (ROS). Herein, self-supporting TiO2 nanotube arrays were engineered with PtPd atom clusters having atomically controlled molar ratio, assembling a dynamic Mott-Schottky catalyst for photocatalytic removal of Microcystin-LR, a toxin produced by cyanobacteria. The separation of photogenerated carriers and the creation of reactive oxygen species (ROS) are optimized by regulating electronic construction via tailoring the Pd ratio in PtPd atom clusters (ca. 4.6 nm in size). The exciton lifetime of the optimum Pt0.9Pd0.1-TiO2 is shortened from 2.51 ns on pure TiO2 to 1.16 ns, and the Gibbs free energy for forming hydroxyl radicals (•OH) varies from −0.826 eV (pure TiO2) to −2.576 eV, powering plentiful •OH when Pt0.9Pd0.1-TiO2 illuminated under solar lights. The kinetic constant of Pt0.9Pd0.1-TiO2 for MC-LR removal is 12.7 times higher than that of the pristine TiO2, presenting exceptional photocatalytic capacity in turning Microcystin-LR into harmless chemicals.