Vertical 3D Printed Pd/TiO 2 Arrays for High Efficiency Photo-assisted Catalytic Water Treatment

C atalytic degradation of organic contaminants is at the frontier of water treatment due to its selectivity, energy savings, and ability to convert harmful contaminants into harmless or even valuable chemical products for recycling. However, achieving sufficiently high performance in the catalytic removal of organic contaminants for practical application is still extremely challenging. Herein, we report a Pd-decorated TiO 2 (Pd/TiO 2 ) hierarchical vertical array for fast and efficient catalytic water treatment. Such a forestlike Pd/TiO 2 vertical array demonstrates the following distinct advantages over conventional planar or bulk catalytic systems: 1) abundant anchoring sites for nanocrystals loading; 2) high sunlight absorption; 3) efficient mass transfer channels for the reactants and products. As a proof of concept, the Pd/TiO 2 array demonstrated rapid and efficient photo-assisted catalytic reduction of high concentrations of 4-nitrophenol wastewater (2 g/L, ca. 14.38 mmol/L) and its feasibility for continuous flow wastewater treatment. The turnover frequency (TOF) value of the Pd/TiO 2 array was up to 8.00 min −1 , which was approximately 4.2 times that of planar Pd/TiO 2 film with the same area (1.91 min −1 ). Our strategy of incorporating nanocatalysts with a hierarchical vertical array provides a promising approach to boosting the catalytic performance of catalysts for different chemical reactions.