catalysts Review Mechanistic Insights into Photodegradation of Organic Dyes Using Heterostructure Photocatalysts Yi-Hsuan Chiu 1 , Tso-Fu Mark Chang 2,*, Chun-Yi Chen 2,*, Masato Sone 2 and Yung-Jung Hsu 1,3,* 1 Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan;
[email protected] 2 Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan;
[email protected] 3 Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu 30010, Taiwan * Correspondence:
[email protected] (T.-F.M.C.);
[email protected] (C.-Y.C.);
[email protected] (Y.-J.H.) Received: 12 April 2019; Accepted: 3 May 2019; Published: 9 May 2019 Abstract: Due to its low cost, environmentally friendly process, and lack of secondary contamination, the photodegradation of dyes is regarded as a promising technology for industrial wastewater treatment. This technology demonstrates the light-enhanced generation of charge carriers and reactive radicals that non-selectively degrade various organic dyes into water, CO2, and other organic compounds via direct photodegradation or a sensitization-mediated degradation process. The overall efficiency of the photocatalysis system is closely dependent upon operational parameters that govern the adsorption and photodegradation of dye molecules, including the initial dye concentration, pH of the solution, temperature of the reaction medium, and light intensity.Additionally, the charge-carrier properties of the photocatalyst strongly affect the generation of reactive species in the heterogeneous photodegradation and thereby dictate the photodegradation efficiency.