Perovskite LaFeO₃/montmorillonite nanocomposites (LaFeO₃/MMT) have been successfully prepared via assembling LaFeO₃ nanoparticles on the surface of montmorillonite with citric acid assisted sol-gel method. The results indicated that the uniform LaFeO₃ nanoparticles were densely deposited onto the surface of montmorillonite, mainly ranging in diameter from 10 nm to 15 nm. The photocatalytic activity of LaFeO₃/MMT was evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation, indicating that LaFeO₃/MMT exhibited remarkable adsorption efficiency and excellent photocatalytic activity with the overall removal rate of RhB up to 99.34% after visible light irradiation lasting for 90 min. The interface characteristic and possible degradation mechanism were explored. The interface characterization of LaFeO₃/MMT suggested that LaFeO₃ nanoparticles could be immobilized on the surface of montmorillonite with the Si-O-Fe bonds. The abundant hydroxyl groups of montmorillonite, semiconductor photocatalysis of LaFeO₃ and Fenton-like reaction could enhance the photocatalytic degradation through a synergistic effect. Therefore, the LaFeO₃/MMT is a very promising photocatalyst in future industrial application to treat effectively wastewater of dyes.

The formation of oxygen vacancies is one of the most critical factors that can improve the electronic and catalytic properties of metal oxides, in which an important challenge is to lower the formation energy of oxygen vacancies at the interface structure. Here we show that clay surfaces rich with hydroxyl groups can induce the formation of oxygen vacancies in metal oxide catalysts. Based on density functional theory calculations, kaolinite is shown to hinder the surface dehydration process of Co₃O₄ nanoparticles, and enhances the charge transfer process at the interface by the highly diffusible protons. Experimental results confirm that vacancy-rich Co₃O₄ is easily produced by a reduction method and kaolinite enhances the formation of oxygen vacancies and divalent cobalt on the nanoparticle surface. As expected, the defective Co₃O₄/kaolinite exhibits enhanced catalytic and electrocatalytic performances. This finding provides an improved way to design efficient clay-based catalysts.