Photocatalytic uranium extraction from radioactive nuclear wastewater and seawater is critical for promoting the sustainable advancement of nuclear industry, but the complexity of real-world environments, particularly the occurrence of anoxic and oxygen-enriched states, presents significant challenges to effective uranium extraction. Here, a layered hollow core–shell structure of Bi₂O₃/g-C₃N₄ Z-scheme heterojunction photocatalyst has been designed and successfully applied for photocatalytic uranium extraction in both aerobic and oxygen-free conditions, and the extraction efficiency of uranium can reach 98.4% and 99.0%, respectively. Moreover, the photocatalyst still has ultra-high extraction efficiency under the influence of pH, inorganic ions, and other factors. The exceptional capability for uranium extraction is on the one hand due to the distinctive hollow core–shell architecture, which furnishes an abundant quantity of active sites. On the other hand, benefiting from the suitable band gap structure brought by the construction of Z-scheme heterojunction, Bi₂O₃/g-C₃N₄ exhibits current densities (1.00 μA/cm²) that are 5.26 and 3.85 times greater than Bi₂O₃ and g-C₃N₄, respectively, and the directional migration mode of Z-scheme carriers significantly prolongs the lifetime of photogenerated charges (1.53 ns), which separately surpass the pure samples by factors of 5.10 and 3.19. Furthermore, the reaction mechanism and reaction process of photocatalytic uranium extraction are investigated in the presence and absence of oxygen, respectively.

Replacing fossil fuels with fuel cells is a feasible way to reduce global energy shortages and environmental pollution. However, the oxygen reduction reaction (ORR) at the cathode has sluggish kinetics, which limits the development of fuel cells. It is significant to develop catalysts with high catalytic activity of ORR. The single-atom catalysts (SACs) of Pt supported on heteroatom-doped graphene are potential candidates for ORR. Here we studied the SACs of Pt with different heteroatoms doping and screened out Pt-C₄ and Pt-C₃O₁ structures with only 0.13 V overpotential for ORR. Meanwhile, it is found that B atoms doping could weaken the adsorption capacity of Pt, while N or O atoms doping could enhance it. This regularity was verified on Fe SACs. Through the electronic interaction analysis between Pt and adsorbate, we explained the mechanism of this regularity and further proposed a new descriptor named corrected d-band center (ε_d-corr) to describe it. This descriptor is an appropriate reflection of the number of free electrons of the SACs, which could evaluate its adsorption capacity. Our work provides a purposeful regulatory strategy for the design of ORR catalysts.

Electrochemical nitrogen reduction reaction (eNRR) is one of the most important chemical reactions for the production of ammonia under ambient environment. However, the lack of in-depth understanding of the structure-activity relationship impedes the development of high-performance catalysts for ammonia production. Herein, the density functional theory (DFT) calculations are performed to reveal the structure–activity relationship for the single-atom catalysts (SACs) supported on g-C₃N₄, which is modified by molecular groups (i.e., H, O, and OH). The computational results demonstrate that the W-based SACs are beneficial to produce ammonia with a low limiting potential (U_L). Particularly, the W-OH@g-C₃N₄ catalyst exhibits an ultralow U_L of −0.22 V for eNRR. And the competitive eNRR selectivity can be identified by the dominant *N₂ adsorption free energy than that of *H. Our findings provide a theoretical basis for the synthesis of efficient catalysts to produce ammonia.