An efficient round-the-clock La2NiO4catalyst for breaking down phenolic pollutants

Abstract

A novel La₂NiO₄ photocatalyst in layered perovskite crystal was synthesized by co-alcoholysis of La(NO₃)₃ and Ni(NO₃)₂ under solvothermal conditions. It exhibited high activity for mineralizing 4-chlorophenol under visible light irradiation and even in the dark, leading to round-the-clock photocatalysis. The photocatalytic mechanism of the La₂NiO₄ in the absence of light irradiation was discussed based on both the structural characterizations and the kinetic studies. Both the La₂NiO₄ crystals and the organic molecules played key roles for starting the degradation reaction in dark. The 4-chlorophenol firstly ionized into anions, followed by donating electrons to La₂NiO₄ owing to the positively charged surface. Then, the electrons could react with dissolved O₂ to produce ˙O₂⁻, which subsequently reacted with H⁺ to form ˙OH radicals. These highly active ˙OH radicals could oxidize 4-chlorophenol into CO₂, leading to complete degradation.