Facile one-pot synthesis of a manganese–cerium dual-doped hydroxyapatite nanocatalyst using Phyllanthus emblica extract for photocatalytic degradation of methylene blue dye and catalytic reduction of 4-nitrophenol

Abstract

In this work, a novel dual-metal-doped hydroxyapatite (HAp) nanocomposite, Mn–Ce/HAp, was synthesized by using Phyllanthus emblica (Indian gooseberry) extract. Advanced characterization tools such as powder X-ray diffraction, ultraviolet diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy, along with energy dispersive X-ray spectroscopy, elemental mapping, transmission electron microscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy, were used to thoroughly characterize the as-synthesized nanocomposite. The photocatalytic and catalytic efficiency of the prepared nanocomposite were investigated in the same study. Mn–Ce/HAp exhibited outstanding performance in methylene blue (MB) dye degradation, with up to 94.8% degradation after just 50 minutes of solar light irradiation. There is no involvement of additional additives in the photodegradation process. HR LC–MS analysis was conducted to determine the major fragments of the degraded dye. A plausible mechanism of photocatalytic degradation was proposed based on various experimental findings. Furthermore, at ambient temperature, the nanocomposite Mn–Ce/HAp demonstrated excellent catalytic activity in the reduction of p-nitrophenol using NaBH₄. The as-prepared nanocatalyst remarkably reduced 4-nitrophenol to 4-aminophenol completely in just 10 s. After five successive reaction cycles, Mn–Ce/HAp still exhibited around 95% of its initial conversion efficiency and photocatalytic efficacy, indicating the high stability and recyclability of the nanocatalyst.