Preparation of FePO4 nano-particles by coupling fast precipitation in membrane dispersion microcontactor and hydrothermal treatment

In this work, a new and simple synthesis route for preparing nanosized iron phosphate with high purity under mild conditions was proposed by coupling fast precipitation and hydrothermal treatment. The fast precipitation between Fe(NO3)3 (with phosphoric acid addition to suppress Fe3+ hydrolysis) and (NH4)3PO4 was carried out in membrane dispersion microcontactor to obtain precursors having narrow size distribution around 50 nm and containing of FePO4 and Fe2(HPO4)3 exclusively. In situ hydrothermal treatment for 1 h in sequence converted Fe2(HPO4)3 to FePO4 and initiated the growth of the original FePO4 particle in precursor. Characterizations of the final product by TEM, XRD, TG/DTA and ICP-OES confirmed it was nanoparticles with iron phosphate hydrate with high purity, well dispersion and narrow size distribution around 59 nm. This coupling process is expectable to be controllable, facile and easy to scale up for nanosized FePO4 production with respect to catalysts, cathode and anode materials.

► A new and simple coupling technique for fabricating nanosized iron phosphate is reported.
► Iron phosphate prepared is about 59 nm and performs excellent in monodispersity and purity.
► A mechanism is proposed to include co-precipitation of nanosized precursors and in situ hydrothermal conversion.
► The micromixing performance during fast precipitation shows critical effect on the morphology of product.