| Summary: | In this study, the relative efficiency of four forms of supported titanium dioxide (TiO<sub>2</sub>) as a photocatalyst to degrade 2,4-dichlorophenoxyacetic acid (2,4-D) in Killex<sup>®</sup>, a commercially available herbicide was studied. Coated glass spheres, anodized plate, anodized mesh, and electro-photocatalysis using the anodized mesh were evaluated under an ultraviolet – light-emitting diode (UV-LED) light source at λ = 365 nm in a semi-passive mode. Energy consumption of the system was used to compare the efficiency of the photocatalysts. The results showed both photospheres and mesh consumed approximately 80 J/cm<sup>3</sup> energy followed by electro-photocatalysis (112.2 J/cm<sup>3</sup>), and the anodized plate (114.5 J/cm<sup>3</sup>). Although electro-photocatalysis showed the fastest degradation rate (K = 5.04 mg L<sup>−1</sup> h<sup>−1</sup>), its energy consumption was at the same level as the anodized plate with a lower degradation rate constant of 3.07 mg L<sup>−1</sup> h<sup>−1</sup>. The results demonstrated that three-dimensional nanotubes of TiO<sub>2</sub> surrounding the mesh provide superior degradation compared to one-dimensional arrays on the planar surface of the anodized plate. With limited broad-scale comparative studies between varieties of different TiO<sub>2</sub> supports, this study provides a comparative analysis of relative degradation efficiencies between the four photocatalytic configurations.
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