Structure, microstructure and photocatalytic properties of embedded spherical Cu nanoparticles on Cu2O–SiO2

Abstract

Nanosized spherical copper particle embedded on oxide matrix (Cunp-Cu2O/SiO2) is synthesized from a low cost chalcopyrite concentrate. The concentrate is reduced by hydrogen at 1323 K, followed by acid leaching to produce Cunp-Cu2O/SiO2. Powder X-ray diffraction confirms the formation of metallic copper as the principal phase along with oxides of silicon and copper. The weight fractions of Cu, SiO2 and Cu2O are 0.565(8), 0.203(2) and 0.232 (3) respectively, as obtained from a three-phase Rietveld refinement. The diameter of copper spheres, rooted on silica, as observed in transmission electron microscopy, is ranging between 4 and 34 nm. Spectroscopic studies, especially Raman spectra, confirm the occurrence of Cu2O. Raman active 2nd overtone at 219 cm−1 appears as the most intense peak. Contribution of SiO2 is clear in Fourier transform infrared spectra. A broad band between 1000 and 1100 cm−1, more specifically at 1080 cm−1 occurs due to Si–O–Si asymmetric stretches. The presence of Cu2O causes photoluminescence peaks to appear in the visible region, corresponding to energy gaps of 0.9 and 1 eV, which indicate the existence of two donor levels below the conduction band. Broad absorption wavelength in the ultraviolet–visible absorption spectra in visible region and low band gap energy of 1.4 eV indicate the possibility of Cunp-Cu2O/SiO2 to be an excellent photocatalytic material. The composite's photocatalytic performance as it is directly derived from the concentrate is quite promising under solar light irradiation. Bromophenol blue (BB) degradation efficiency is 71.26% in 90 min, the photocatalytic kinetics rate is 0.01447 min−1. Characterizations of Cunp-Cu2O/SiO2 as the recycled photocatalyst confirm its photocatalytic stability.