NiS@CdS interfacial Schottky junction boosting spatial charge separation for highly efficient photocatalytic reduction of U(VI)

Effective uranium (U) removal from U-containing wastewater is pivotal to the sustainable development of the nuclear power industry. Photocatalysis is a promising technique and more effort is needed for designing more efficient photocatalysts. Here, NiS@CdS interfacial Schottky junction photocatalysts with different Ni/Cd molar ratios are synthesized. Under 90 min solar light irradiation, U(VI) removal efficiency from simulated U-containing wastewater is up to ∼99 %, and high recyclability after five cycles, 95.3 %, are obtained with Ni/Cd = 0.33 added for the synthesis. These are due to favorable Zeta potential and optical characteristics, narrow band gap and high stability of the composite. Besides, density functional theory (DFT) calculation illustrates the existence of interfacial Schottky junction between CdS and NiS, which may boost the spatial charge separation. Moreover, X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) characterizations show that U(VI) is successfully reduced to uraninite. This work potentially helps opening a new avenue for cost-effective U removal from U-containing wastewater.