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

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 1D cone structure 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 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 practical uranium separation from aqueous solutions with inexhaustible solar energy and minimal electrical energy.