Perovskite LaNiO3/Ag3PO4 heterojunction photocatalyst for the degradation of dyes

Abstract

Pristine lanthanum nickelate (LaNiO₃), silver phosphate (Ag₃PO₄) and perovskite lanthanum nickelate silver phosphate composites (LaNiO₃/Ag₃PO₄) were prepared using the facile hydrothermal method. Three composites were synthesized by varying the percentage of LaNiO₃ in Ag₃PO₄. The physical properties of as-prepared samples were studied by powder X-ray diffraction (pXRD), Fourier-transform infrared (FT-IR), Scanning electron microscopy (SEM) and Energy-dispersive X-ray (EDX). Among all synthesized photocatalysts, 5%LaNiO₃/Ag₃PO₄ composite has been proved to be an excellent visible light photocatalyst for the degradation of dyes i.e., rhodamine B (RhB) and methyl orange (MO). The photocatalytic activity and stability of Ag₃PO₄ were also enhanced by introducing LaNiO₃ in Ag₃PO₄ heterojunction formation. Complete photodegradation of 50 mg/L of RhB and MO solutions using 25 mg of 5%LaNiO₃/Ag₃PO₄ photocatalyst was observed in just 20 min. Photodegradation of RhB and MO using 5%LaNiO₃/Ag₃PO₄ catalyst follows first-order kinetics with rate constants of 0.213 and 0.1804 min^-1, respectively. Perovskite LaNiO₃/Ag₃PO₄ photocatalyst showed the highest stability up to five cycles. The photodegradation mechanism suggests that the holes ( h ⁺) and superoxide anion radicals $\left({\left(O\right)}_2^{•-}\right)$ plays a main role in the dye degradation of RhB and MO.

Keywords: dyes; lanthanum nickelate; photocatalysis; silver phosphate; water pollution.