The use of metal-based heterogeneous catalysts for the degradation of N-containing organic dyes has attracted much attention due to their excellent treatment efficiency and capability. Here, we report the synthesis of heterometals (Ni and Pd)-incorporated Fe₃O₄ (Ni-Pd/Fe₃O₄) yolk-shelled nanospheres for the catalytic reduction of N-containing organic dyes using a facile combination of solvothermal treatment and high-temperature annealing steps. Benefiting from the magnetic properties and the yolk-shelled structure of the Fe₃O₄ support, as well as the uniformly dispersed active heterometals incorporated in the shell and yolk of spherical Fe₃O₄ nanoparticles, the as-prepared Ni-Pd/Fe₃O₄ composite shows excellent recyclability and enhanced catalytic activity for three N-containing organic dyes (e.g., 4-nitrophenol, Congo red, and methyl orange) compared with its mono metal counterparts (e.g., Ni/Fe₃O₄ and Pd/Fe₃O₄). In the 4-nitrophenol reduction reaction, the catalytic activity of Ni-Pd/Fe₃O₄ was superior to many Fe₃O₄-supported nanocatalysts reported within the last five years. This work provides an effective strategy to boost the activity of iron oxide-based catalytic materials via dual or even multiple heterometallic incorporation strategy and sheds new light on environmental catalysis.

A two-dimensional/two-dimensional (2D/2D) TiO₂/ZnIn₂S₄ photocatalyst was reasonably proposed and constructed by a two-step oil bath-hydrothermal method. TiO₂ nanosheets uniformly grown on the surface of ZnIn₂S₄ nanosheets and a synergetic effect between the TiO₂ and ZnIn₂S₄ could highly contribute to improving the specific surface area and hydrophilicity of ZnIn₂S₄ as well as accelerating the separation and transfer of photon-generated e⁻-h⁺ pairs, and thus enhancing the visible-light photocatalytic degradation and H₂ evolution performance of ZnIn₂S₄. Rhodamine B (RhB) and tetracycline (TC) were simultaneously selected as the target pollutants for degradation in the work. The optimum photocatalytic RhB and TC degradation properties of TiO₂/ZnIn₂S₄-10 wt% were almost 3.11- and 8.61-fold higher than that of pure ZnIn₂S₄, separately, while the highest photocatalytic hydrogen evolution rate was also observed in the presence of TiO₂/ZnIn₂S₄-10wt% and 4.28-fold higher than that of ZnIn₂S₄. Moreover, the possible photocatalytic mechanisms for enhanced visible-light photocatalytic degradation and H₂ evolution were investigated and proposed in detail. Our research results open an easy pathway for developing efficient bifunctional photocatalysts.