Fe₂O₃ nanopowders prepared by a thermal plasma process for water oxidation

Highlights: • Hematite nanopowders with a high purity were synthesized by a DC thermal plasma process. • Fe₃O₄ is formed during the formation of Fe₂O₃ by thermal plasma with iron and oxygen sources. • Hematite nanopowders with a high purity show higher PEC performance compared to mixed oxides. - Abstract: Hematite (Fe₂O₃) nanopowders were synthesized from commercially available micro-sized iron powders by a DC thermal plasma process at atmospheric pressure. The micro-sized iron powders were vaporized in the plasma region, after which the plasma processing equipment was rapidly quenched, resulting in the formation of iron nanopowders with a size of less than 100 nm. Subsequently, the iron nanopowders were heated to convert hematite with a high purity, which was then formed into a thin film with a binder for preparation of electrodes for photoelectrochemical water oxidation. Iron oxide nanopowders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analysis (PSA) and transmission electron microscopy (TEM). The photoelectrochemical properties of the Fe₂O₃ film were characterized in 1 M NaOH under AM 1.5 conditions