title: Multilayer Heterojunction Anodes for Saline Wastewater Treatment: Design Strategies and Reactive Species Generation Mechanisms.
abstract: Multilayer heterojunction SbSn/CoTi/Ir anodes, which consist of Ir0.7Ta0.3O2 bottom layers coated onto a titanium base, Co-TiO2 interlayers, and overcoated discrete Sb-SnO2 islands, were prepared by spray pyrolysis. The Ir0.7Ta0.3O2 bottom layer serves as an Ohmic contact to facilitate electron transfer from semiconductor layers to the Ti base. The Co-TiO2 interlayer and overcoated Sb-SnO2 islands enhance the evolution of reactive chlorine. The surficial Sb-SnO2 islands also serve as the reactive sites for free radical generation. Experiments coupled with computational kinetic simulations show that while ·OH and Cl· are initially produced on the SbSn/CoTi/Ir anode surface, the dominant radical formed in solution is the dichlorine radical anion, Cl2·(-). The steady-state concentration of reactive radicals is 10 orders of magnitude lower than that of reactive chlorine. The SbSn/CoTi/Ir anode was applied to electrochemically treat human wastewater. These test results show that COD and NH4(+) can be removed after 2 h of electrolysis with minimal energy consumption (370 kWh/kg COD and 383 kWh/kg NH4(+)). Although free radical species contribute to COD removal, anodes designed to enhance reactive chlorine production are more effective than those designed to enhance free radical production.
authors.affiliation: Linde + Robinson Laboratories California Institute of Technology Pasadena, California 91125, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Linde + Robinson Laboratories California Institute of Technology Pasadena, California 91125, United States.
authors.forename: Jieun
authors.initials: J
authors.lastname: Shin
authors.affiliation: Linde + Robinson Laboratories California Institute of Technology Pasadena, California 91125, United States.
authors.forename: Justin T
authors.initials: JT
authors.lastname: Jasper
authors.affiliation: Linde + Robinson Laboratories California Institute of Technology Pasadena, California 91125, United States.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hoffmann
mesh_terms: D004566:Electrodes; D004572:Electrolysis; D010084:Oxidation-Reduction; D014025:Titanium / Q000737:chemistry; D062065:Wastewater / Q000737:chemistry*
chemical_list: D014025:Titanium; D062065:Wastewater