Preparation of CuCrO₂ and the photocatalytic properties of its composites

Delafossite CuCrO₂ was prepared with Cr(NO₃)₃ and Cu(NO₃)₂ by the semi-wet method via two different routes. The samples were characterized with thermogravimetry-differential scanning calorimetry, X-ray diffraction, diffuse reflectance ultraviolet-visible spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy techniques. It was shown that addition of Cr(OH)₃ precipitated with aqueous ammonia solution into aqueous Cu(NO₃)₂ solution is a suitable route to synthesize CuCrO₂. In the calcination process, the precursor transformed into CuCrO₂ in the sequence: Cr(OH)₃ → CuCrO₄ → CuCr₂O₄ → CuCrO₂, as verified by the TG-DSC and XRD results. The composites of CuCrO₂-WO₃ and CuCrO₂-ZnO prepared by the grinding method show higher activity than CuCrO₂ in the photocatalytic splitting of water into hydrogen under the irradiation of a high-pressure mercury lamp or a xenon lamp.