Ammonium iron(II) sulfate is widely used as a source of Fe
2+ ions because of its high solubility in water and because it oxidizes much more slowly in air than other ferrous salts like iron(II) sulfate. Consequently, the reagent finds broad applications from analytical titrations to aqueous redox chemistry as a reducing agent. Researchers often use ammonium iron(II) sulfate as a source of Fe
2+ to synthesize iron-containing nanoparticles. For example, to synthesize magnetite (Fe
3O
4) nanoparticles, researchers
co-precipitate aqueous solutions of ammonium iron(II) sulfate with a source of Fe
3+, like FeCl
3[1] or NH
4Fe(SO
4)
2 [2]. Ammonium iron(II) sulfate also serves as a precursor in the synthesis of iron(III) oxide-hydroxide (FeOOH)
[3] nanosheets and as reagents to dope metal oxide-hydroxide nanosheets with iron.
[4] Ammonium iron(II) sulfate is also well-suited to make olivine LiFePO
4 by the
co-precipitation method. In this method, aqueous solutions of ammonium iron(II) sulfate are mixed with ammonium phosphate and
co-precipitated with lithium hydroxide.
[5] One advantage of this synthetic strategy is that it enables the
in-situ formation of nanocomposites like LiFePO
4/graphene.
[6]