Citric Acid Affects Tungsten Oxide

In the synthesis of tungsten oxide, ammonium tungstate may be added as the tungsten source. The addition of citric acid can effectively control the morphology of tungsten oxide. Hydrothermal synthesis of tungsten oxide by adding tartaric acid and citric acid and other organic acids can affect the tungsten oxide nanomaterials relative growth rate of different crystal planes to effectively control the tungsten oxide crystal growth and morphology.

Ammonium metatungstate and citric acid were used as raw materials to synthesize hexagonal tungsten oxide successfully by hydrothermal method. By changing the amount of citric acid added, the morphology of tungsten oxide changes from nanosheet to nanorods or nanowires. This shows that citric acid in the control of the synthesis of tungsten oxide morphology and its crystal growth has a very important significance. This is because citric acid has three carboxyl groups, and carboxyl groups can form chelates with tungsten atoms through covalent bonds. In this way, relatively stable tungsten oxide colloidal particles can be obtained, thereby controlling the crystal growth of the synthesized product during hydrothermal synthesis.

In addition, citric acid has a certain reduction ability, contribute to the tungsten oxide surface to form many defects. Use of ammonium tungstate and sulfuric acid solution hydrothermal method. Hexagonal phase tungsten oxide nanorods grown in the (110) direction can be synthesized. By hydrothermally changing the type of acid and tungsten source, the growth direction of the resulting tungsten oxide crystals can be explored.

The tungsten source has a great influence on the growth direction of hexagonal phase tungsten oxide, while the type of acid has no effect on the growth direction of the hexagonal phase tungsten oxide. The analysis and comparison of the high resolution and XRD patterns of the synthesized samples of different tungsten oxides show that the presence of ammonium ions enables the growth of tungsten oxide to grow in the (110) or (001) direction. This is because the ammonium ions strongly adsorb on the (001) crystal plane, hindering the crystal growth along the (001) direction, and the growth of the hexagonal tungsten oxide is mainly in the (110) direction.

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