Acidic Peptizing Agent Effect on Anatase-Rutile Ratio and Photocatalytic Performance of TiO2 Nanoparticles

Hatem A Mahmoud,Kamal M S Khalil,Tarek T Ali,Katabathini Narasimharao

doi:10.1186/s11671-018-2465-x

Hatem A Mahmoud, Kamal M S Khalil + Show 2 more

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https://doi.org/10.1186/s11671-018-2465-x

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Abstract

TiO2 nanoparticles were synthesized from titanium isopropoxide by a simple peptization method using sulfuric, nitric, and acetic acids. The effect of peptizing acid on physicochemical and photocatalytic properties of TiO2 powders was studied. The structural properties of synthesized TiO2 powders were analyzed by using XRD, TEM, N2-physisorption, Raman, DR UV-vis, FTIR, and X-ray photoelectron spectroscopy techniques. The characterization results showed that acetic acid peptization facilitated the formation of pure anatase phase after thermal treatment at 500 °C; in contrast, nitric acid peptization led to a major rutile phase formation (67%). Interestingly, the sample peptized using sulfuric acid yielded 95% anatase and 5% rutile phases. The photocatalytic activity of synthesized TiO2 nanoparticles was evaluated for degradation of selected organic dyes (crystal violet, methylene blue, and p-nitrophenol) in aqueous solution. The results confirmed that the TiO2 sample peptized using nitric acid (with rutile and anatase phases in 3:1 ratio) offered the highest activity for degradation of organic dyes, although, TiO2 samples peptized using sulfuric acid and acetic acid possessed smaller particle size, higher band gap energy, and high surface area. Interestingly, TiO2 sample peptized with nitric acid possessed relatively high theoretical photocurrent density (0.545 mAcm−2) and pore diameter (150 Å), which are responsible for high electron-hole separation efficiency and diffusion and mass transportation of organic reactants during the photochemical degradation process. The superior activity of TiO2 sample peptized with nitric acid is due to the effective transfer of photogenerated electrons between rutile and anatase phases.

Highlights

Titanium dioxide (TiO2) is a widely known semiconductor material for its use in many applications, including solar energy conversion, pollution control, and photocatalysis [1–3]
We examined the influence of nature of peptizing acid (H2SO4, HNO3, and CH3COOH) on the formation of rutile phase and its influence in the photocatalytic efficiency of Titanium oxide (TiO2) nanoparticles in the degradation of three different organic pollutants (crystal violet (CV), methylene blue (MB), and p-nitrophenol (p-para–nitro phenol (NP)))
The TiO2 sample peptized with acetic acid possessed pure anatase phase, while the formation of minor (5%) and major (67%) of rutile phase was observed in case of samples peptized with sulfuric acid and nitric acid, respectively

Summary

Introduction

Titanium dioxide (TiO2) is a widely known semiconductor material for its use in many applications, including solar energy conversion, pollution control, and photocatalysis [1–3]. TiO2 generally has three polymorphs, namely anatase, rutile, and brookite. It was reported that anatase and brookite can be transformed into rutile after thermal treatment at high temperature (< 610 °C) [4, 5]. TiO2 anatase is known to be an active photocatalyst for degradation of organic pollutants [1, 5–8]. It was observed that the size, crystalline phase, and porosity of the TiO2 samples have a strong influence over their applications [9].

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