An efficient photocatalyst prepared via a low-cost method is important for the effective removal of persistent organic dyes from water pollution. These dyes are stable and difficult to break down, so an effective photocatalyst with a suitable band gap is needed. MWCNT, ZrO2, and Y2O3 have been explored as photocatalysts for wastewater treatment due to their unique physiochemical properties. However, their performance is limited by a wide band gap, rapid electron–hole recombination, and inefficient charge separation. Hence, further modification and optimization of these materials are essential to achieve superior pollutant removal performance. Therefore, in this study, ZrO2/MWCNT and Y–ZrO2/MWCNT hybrid composites were synthesized via an ultrasonic-assisted hydrothermal method to evaluate their photocatalytic efficiency for the degradation of organic dyes. The structural, optical and morphological properties of the prepared samples were examined using XRD, FTIR, UV–Visible spectroscopy, SEM and TEM. XRD analysis confirms the formation of a monoclinic crystalline phase of ZrO2, while FTIR spectra indicate the presence of Zr–O and Y–O bonds. EDS and elemental mapping further confirms the composition and uniform surface distribution of the constituent elements. The Y–ZrO2/MWCNT hybrid composite, with a band gap of 2.13 eV and an average crystallite size of 24 nm, exhibits notable catalytic activity toward the degradation of RhB. The photocatalytic activity was evaluated by degrading RhB dye under UV light irradiation and different experimental conditions were tested to understand the performance of the materials. Among all the samples, the Y-ZrO2/MWCNT hybrid composite showed the highest degradation efficiency. A degradation efficiency of 95.7% was achieved at a catalyst dosage of 1 g L⁻¹, with an initial RhB concentration of 30 ppm at pH 10, under UV–visible light irradiation for 140 min. This improved activity can be attributed to the synergistic effect of yttrium doping and MWCNT, which enhances charge separation and reduces recombination of electron and hole pairs. Scavenger analysis indicates that the degradation of RhB is mainly governed by superoxide radicals (O₂•⁻) and holes (h⁺), with electrons (e⁻) also contributing to the process. The maximum degradation efficiency obtained was 87.3% for ZrO2/MWCNT and 95.7% for Y-ZrO2/MWCNT hybrid composite. These results clearly show that yttrium doping improves the photocatalytic performance of the composite material. Graphical abstract Graphical illustration of Y-ZrO2/MWCNT hybrid composite and Photocatalytic performance

Photocatalytic degradation of Rhodamine B dye: MWCNT, ZrO2/MWCNT and Y-ZrO2/MWCNT hybrid composites as potential photocatalysts

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发表日期：

2026年6月17日

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C. Kalaiyarasi,
P. Dhilip,
A. Dhivya,
P. Sivakumar

摘要

An efficient photocatalyst prepared via a low-cost method is important for the effective removal of persistent organic dyes from water pollution. These dyes are stable and difficult to break down, so an effective photocatalyst with a suitable band gap is needed. MWCNT, ZrO₂, and Y₂O₃ have been explored as photocatalysts for wastewater treatment due to their unique physiochemical properties. However, their performance is limited by a wide band gap, rapid electron–hole recombination, and inefficient charge separation. Hence, further modification and optimization of these materials are essential to achieve superior pollutant removal performance. Therefore, in this study, ZrO₂/MWCNT and Y–ZrO₂/MWCNT hybrid composites were synthesized via an ultrasonic-assisted hydrothermal method to evaluate their photocatalytic efficiency for the degradation of organic dyes. The structural, optical and morphological properties of the prepared samples were examined using XRD, FTIR, UV–Visible spectroscopy, SEM and TEM. XRD analysis confirms the formation of a monoclinic crystalline phase of ZrO₂, while FTIR spectra indicate the presence of Zr–O and Y–O bonds. EDS and elemental mapping further confirms the composition and uniform surface distribution of the constituent elements. The Y–ZrO₂/MWCNT hybrid composite, with a band gap of 2.13 eV and an average crystallite size of 24 nm, exhibits notable catalytic activity toward the degradation of RhB. The photocatalytic activity was evaluated by degrading RhB dye under UV light irradiation and different experimental conditions were tested to understand the performance of the materials. Among all the samples, the Y-ZrO₂/MWCNT hybrid composite showed the highest degradation efficiency. A degradation efficiency of 95.7% was achieved at a catalyst dosage of 1 g L⁻¹, with an initial RhB concentration of 30 ppm at pH 10, under UV–visible light irradiation for 140 min. This improved activity can be attributed to the synergistic effect of yttrium doping and MWCNT, which enhances charge separation and reduces recombination of electron and hole pairs. Scavenger analysis indicates that the degradation of RhB is mainly governed by superoxide radicals (O₂•⁻) and holes (h⁺), with electrons (e⁻) also contributing to the process. The maximum degradation efficiency obtained was 87.3% for ZrO₂/MWCNT and 95.7% for Y-ZrO₂/MWCNT hybrid composite. These results clearly show that yttrium doping improves the photocatalytic performance of the composite material.

Graphical abstract

Graphical illustration of Y-ZrO₂/MWCNT hybrid composite and Photocatalytic performance