Self-supportive Three-Way Photoelectrochemical System Achieving Uranium Recycling, Organic Oxidation, and Electricity Generation in Complex Waters

Abstract

A self-sustaining solar photoelectrochemical cell (SS-PEC) is present that recovers uranium from aqueous uranyl ions (UO₂²⁺) with concurrent organic oxidation and electricity production. The employed a titanium dioxide (TiO₂) nanorod array photoanode (monolithically combined with a back Si solar cell) directly captures electrons from organic compounds, leading to the oxidation of organic compounds and the decomposition of uranium-organic complexes. On the other hand, uranyl ions can be efficiently adsorbed and reduced on a three-dimensional (3D) vanadium sulfide (VS₄) nanowire decorated carbon fiber felt (VS/CF) cathode. The chain-like crystal structure of VS with exposed S₂²⁻ dimers favors the charge transfer and coordination with UO₂²⁺, while the V⁵⁺/V⁴⁺/V³⁺ redox cycle facilitates the reductive recovery of UO₂²⁺. Consequently, organics are continuously photooxidized on the anode to provide electrons for reducing UO₂²⁺ on the cathode with accompanying the electric current generation through the PEC cell. The proposed SS-PEC system successfully operated in various complex water systems, including real uranium tailings wastewater, with high stability (for 30 repeated uses without obvious decay) and uranium recycling efficiency (92%). The excellent selectivity for UO₂²⁺ adsorption on VS/CF is demonstrated by the far higher distribution coefficient K_d (14,173 mL g⁻¹) compared with other competing ions.