Construction of a Hierarchical Core–Shell Z-Scheme Two-Dimensioanl/Two-Dimensional ZnIn2S4@TpBpy Heterostructure for Photocatalytic Reduction of U(VI)

The essential nature of the photocatalytic process is charge transfer. To optimize the spatial separation of photogenerated electron–hole (e–-h+) pairs for high-performance catalytic efficiency, in this work, we have successfully prepared hierarchical core–shell two-dimensional (2D)/2D ZnIn2S4@TpBpy (ZIS@TpBpy) with well-matched Z-scheme interfacial charge transfer channels for uranium (U(VI)) photoreduction. The Z-scheme electron transfer configuration was confirmed by internal electric field (IEF) formation analysis, XPS characterization, and DMPO spin-trapping EPR spectroscopy. With large specific surface area and abundant active sites, the ZIS@TpBpy composite achieved a U(VI) extraction rate of 94.08%. In addition, the removal rate constant of ZIS@TpBpy (0.0137 min–1) was 2.05 and 4.28 times higher than those of TpBpy (0.0067 min–1) and ZnIn2S4 (0.0032 min–1), respectively. First, the combination of organic and inorganic components expanded the range of visible light absorption and utilization. Afterward, under visible-light irradiation, more photogenerated e–-h+ pairs dissociated and migrated to the ZnIn2S4 surface driven by the IEF and Z-scheme heterostructure. Simultaneously, the synergistic effect between the polarization potential generated by the IEF in the ZIS@TpBpy composite and abundant active sites (N and O atoms) in the TpBpy framework further accelerated the depletion and translocation of photogenerated e–-h+ pairs, which significantly improved the efficiency of photocatalytic reduction of U(VI).