Thin‐Film Electrodeposition of a Fe ₃ (NH ₄ )H ₈ (PO ₄ ) ₆ .6H ₂ O Superphosphate Material by Oxidation of Mohr's Salt in a Phosphoric Medium

Abstract The superphosphate thin film of Fe 3 (NH 4 )H 8 (PO 4 ) 6 .6H 2 O was electrodeposited using a concentrated solution of 2 M phosphoric acid and a Mohr's salt precursor (Fe(NH 4 ) 2 (SO 4 ) 2 .6H 2 O). The electrochemical oxidation of the Fe(H 2 PO 4 ) + complex present in the medium was monitored by cyclic voltammetry and showed that the deposition resulted from a combination of different phenomena, such as diffusion and adsorption. The electrodeposition was carried out using the chronoamperometric method at a potential of 0.6 V/SCE. The resulting material was studied by X‐ray diffraction (XRD) and has a hexagonal structure corresponding to the P31c space group, with lattice parameters of a = 9.15 Å and c = 16.86 Å; its morphology was studied by scanning electron microscopy combined with energy dispersive X‐ray spectroscopy (SEM/EDS), which showed a rod structure and confirmed the presence of its constituent elements. Fourier transform infrared spectroscopy (FTIR) revealed lattice vibration bands associated with (PO 4 ) 3 – ions and water molecules. Meanwhile, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) indicated water loss at around 187 °C.