Boosting photocatalytic reduction of uranium by sulfur-doped zinc ferrate nanoparticles: Impacts of shallow energy levels and light intensity

A critical aspect of the design of photocatalytic materials is the prevention of recombination of photogenerated carriers to maximize the photocatalytic efficiency for the removal of U(VI). Herein, the sulfur successfully integrated into co-precipitated zinc ferrate nanoparticles (ZFO) and nitrogen-doped zinc ferrate nanoparticles (N-ZFO) through a hydrothermal method, which exhibit exceptional photocatalytic activity under various lighting conditions. Compared to conventional ZFO, the bandgap energy of sulfur-doped ZFO was found to be narrower, and the charge carrier separation and transfer rates were higher, which are beneficial for the reduction of U(VI) by photoelectrons. Among these, the co-precipitated ZnFe₂O₄ demonstrated a U(VI) reduction efficiency that was four times that of N-ZFO, and the reduction effect of S₆-ZFO on U(VI) was 1.21 times and 1.08 times that of ZFO and S₁₅–N-ZFO, respectively. The photocatalytic activity of S₆-ZFO under natural light conditions exhibits diverse behaviors: 418.49 μmol/(g·h) on sunny days, 198.95 μmol/(g·h) on cloudy days, and 40.55 μmol/(g·h) on rainy days. Remarkably, it retains good photocatalytic activity even under a light intensity of 1000 Lux, offering a valuable strategy for the development of high-performance low-light photocatalysts. This breakthrough work offers a unique interfacial engineering approach capable of enhancing the removal of U(VI).