[Paper Review] Enhancement of photocatalytic performance of V2O5 by rare-earth ions doping, synthesized by facile hydrothermal technique

M. H. Kabir, Md. Zakir Hossain+8 more|arXiv (Cornell University)|Jan 17, 2023

Transition Metal Oxide NanomaterialsMaterials Science3 citations

TL;DR

This study enhances the photocatalytic performance of V2O5 through doping with holmium (Ho) and ytterbium (Yb) rare-earth ions using a facile hydrothermal synthesis method. Doping at 3 mol.% significantly improves visible-light-driven degradation efficiency, achieving 93% and 95% degradation of organic pollutants within 2 hours, respectively, due to optimized bandgap and reduced charge recombination.

ABSTRACT

The rare-earth (RE) elements [Holmium (Ho) and Ytterbium (Yb)] doped vanadium pentoxide (V2O5) with a series of doping concentrations (1 mol.%, 3 mol.%, and 5 mol.%) have been successfully synthesized using environment-friendly facile hydrothermal method. The effect of RE ions on the photocatalytic efficiency of doped V2O5 has also been analyzed. The stable orthorhombic crystal structure of doped V2O5 confirms by the X-ray diffraction with no secondary phase, and high-stressed conditions are generated for the 3 mol.%. The crystallite size, strain, and dislocation density are calculated to perceive the doping effect on the bare V2O5. The optical characteristics have been measured using UV-vis spectroscopy. The absorptions are found to be increased with increasing doping concentrations; however, the bandgap remains in the visible range. The photocatalytic properties are examined for the compounds with varying pH, and it is observed that higher efficiency is exhibited for the pH 7 and catalyst concentration 500 ppm. The highest degradation efficiency is found to be 93% and 95% for the 3 mol.% of Ho and Yb-doped V2O5 samples within 2 hours, respectively. It is elucidated that the RE ions significantly impact the catalytic behavior of V2O5, and the mechanism behind these extraordinary efficiencies has been explained thoroughly.

Motivation & Objective

• To improve the photocatalytic efficiency of V2O5 under visible light irradiation.
• To investigate the impact of rare-earth ion doping (Ho and Yb) on the structural and optical properties of V2O5.
• To optimize doping concentration and reaction conditions (pH, catalyst loading) for maximum degradation efficiency.
• To understand the mechanism behind enhanced photocatalytic performance due to rare-earth doping.
• To develop an environmentally friendly, scalable hydrothermal synthesis route for doped V2O5 materials.

Proposed method

• Synthesis of Ho- and Yb-doped V2O5 via a facile hydrothermal method at controlled temperature and duration.
• X-ray diffraction (XRD) analysis to confirm the orthorhombic crystal structure and detect secondary phases.
• UV-vis diffuse reflectance spectroscopy to determine bandgap energy and optical absorption characteristics.
• Calculation of crystallite size, lattice strain, and dislocation density from XRD peak broadening using the Scherrer and Williamson-Hall equations.
• Photocatalytic degradation experiments using model pollutants under visible light, varying pH and catalyst concentration (500 ppm optimal).
• Systematic evaluation of degradation efficiency over time to quantify catalytic performance at different doping levels.

Experimental results

Research questions

• RQ1 How does rare-earth ion doping (Ho and Yb) affect the crystal structure and phase purity of V2O5?
• RQ2 What is the optimal doping concentration (1, 3, 5 mol.%) for maximizing photocatalytic degradation efficiency?
• RQ3 How do pH and catalyst concentration influence the photocatalytic performance of doped V2O5?
• RQ4 What is the role of rare-earth ions in reducing charge recombination and enhancing visible-light absorption?
• RQ5 What is the underlying mechanism responsible for the enhanced photocatalytic activity in Ho- and Yb-doped V2O5?

Key findings

• Ho-doped V2O5 at 3 mol.% achieved 93% degradation efficiency of organic pollutants within 2 hours under visible light.
• Yb-doped V2O5 at 3 mol.% exhibited the highest degradation efficiency of 95% within the same timeframe.
• XRD analysis confirmed the stable orthorhombic structure of doped V2O5 with no secondary phases, indicating solid solution formation.
• The bandgap of doped V2O5 remained within the visible light range, with increased absorption intensity at higher doping concentrations.
• Lattice strain and dislocation density increased significantly at 3 mol.% doping, indicating structural distortion that may enhance charge separation.
• Optimal photocatalytic performance was observed at pH 7 and a catalyst concentration of 500 ppm, indicating pH-dependent surface charge and reactivity.