One-dimensional nanostructure arrays with Schottky Junction enhanced charge separation for the photoelectrocatalytic selective removal of Uranium from wastewater

Abstract

The photoelectrocatalytic reduction of soluble U(VI) to relatively insoluble U(IV) is a promising method for uranium wastewater treatment. However, the strong reliance on sacrificial agents and an inert atmosphere due to the rapid charge reorganization remains a great challenge. The construction of an inner electrical field at a heterojunction interface accompanied by an external electric field provides a promising strategy for enhancing charge transfer. Herein, a photoelectrode was proposed by in-situ coating nano-TiO2 cone arrays (NTCA) on a titanium mesh, and used for uranium removal from complex effluents under air conditions without sacrificial agents. The enhanced spatial charge separation driven by the Schottky junction built-in electric field and an external bias voltage, coupled with rapid fluid diffusion, granted the photoelectrode an outstanding photoelectrocatalytic uranium removal performance with photocurrent densities of up to 3 mA cm−2 at −0.55 VAg/AgCl. The impressive uranium removal performance was maintained in a wide range of chemical conditions, as well as in real seawater and industrial wastewater. Theoretical calculation revealed that uranyl ions were confined on the NTCA surface as [UO2(H2O)5]2+, further reduced to UO2. This work demonstrated a viable route for uranium separation from aqueous solutions with inexhaustible solar energy and minimal electrical energy.