Synthesis and Characterization of Nitrogen‐Doped Group IVB Visible‐Light‐Photoactive Metal Oxide Nanoparticles

Abstract

The incorporation of main group elements into wide-bandgap semiconductors has attracted significant interest because of the potential for modifying the physical properties of these semiconductors, as well as for applications such as photocatalysis, water splitting, and optoelectronics. [1][2][3] Among the main group elements, nitrogen is believed to be the most favorable p-type dopant because of its similar size to oxygen, metastable AX center formation, and small ionization energy.[4] For example, the incorporation of N into ZnO has been found to be a very promising way to make p-type ZnO, which represents a potentially useful alternative to toxic and expensive III-V semiconductors for applications such as light-emitting devices (LEDs). [2,5,6] Another exciting example is visible-light-active TiO 2 , which is a promising material for applications such as water splitting and photocatalysis. [1,[7][8][9][10] Owing to its potential role in solving the inevitable global energy and environment crises, N-doped TiO 2 has received a great deal of attention in recent years. Although several theoretical and experimental studies have validated the efficacy of the N doping of TiO 2 for a variety of applications, [1,8,[10][11][12][13][14][15][16][17] the different approaches used for N doping have raised questions about the origin of the observed photocatalytic activity. In order to increase the understanding of N doping at the nanoscale level, it is imperative to carry out a systematic analysis of the photocatalytic activities of nanoparticles with different N-doping levels and metal oxide matrices to aid the development of a new generation of photocatalysts. [18,19] However, from a survey of the literature, no such study has been conducted up till now. Here, we present the incorporation of controlled amounts of N into group IVB metal oxide (TiO 2 , ZrO 2 , and HfO 2 ) nanoparticles via a reliable wet-chemical procedure under ambient conditions. Furthermore, we present the effects of doping on their optical and photocatalytic properties. The synthesis of N-doped group IVB metal oxides is based on our previously reported sol-gel approach. [8,9,20] We have determined from the X-ray photoelectron spectroscopy (XPS) analysis of N-doped TiO 2 [9,20] that coordinating the amine precursor to the Ti precursor (usually Ti[OCH 2 (CH 3 ) 2 ] 4 ) is essential for the efficient N doping of metal oxides. In the present synthetic route, we first attach the amine to the central metal to form an amino-coordinated precursor complex; subsequently, we hydrolyze the precursor solution with distilled water. Under different pH conditions it is possible to obtain TiO 2 slurries with different amounts of incorporated nitrogen. In addition, the particle size can be confined to the nanometer regime by controlling the rate of water addition. After washing, the dispersions are centrifuged and the obtained powders are dried under vacuum. The dried powders are yellow to orange in color depending on the doping level. Before characterization, the products ...

Synthesis, Characterization and Photocatalytic Performance of TiO2 Codoped with Bismuth and Nitrogen

“…This has been demonstrated in several systems, such as N-Sn [29], N-Fe [30], N-W [31], N-B [32], N-F [33,34], N-Ag [35], N-Pd [36] and N-C-F [37]. Bi-doped TiO 2 photocatalysts are especially concerned with high photocatalytic activities even under visible light in recent several reports [38][39][40][41][42][43].…”

Low temperature hydrothermal synthesis of N-doped TiO2 photocatalyst with high visible-light activity

“…It is interesting that the pH value in the preparation process greatly affected the doping nitrogen concentration and consequently on the photocatalytic activity of N-TiO 2 photocatalysts [40,48,49]. In order to investigate the effects of pH value in the process of preparing the photocatalysts on the photocatalytic activity, the pH value of the TiO 2 sol was adjusted by HNO 3 solution Fig.…”

Simple Preparation of Anatase Titanium Dioxide Nanoparticles by Heating Titanium-Organic Frameworks

“…A variety of nitrogen sources are available as dopant precursors such as nitrate, aliphatic amines, ammonia, ammonium salts, or urea. [24][25][26][27] In spite of the current debate on the origin or mechanism, 23 N-doped TiO 2 materials are known to show significant visible light activity compared to unmodified TiO 2 .…”