Precursor-mediated synthesis of Cu2−xSe nanoparticles and their composites with TiO2 for improved photocatalysis

Abstract

The direct synthesis of copper selenide nanoparticles from the reaction of ditertiarybutyl selenide ^tBu₂Se with copper(II) trifluoroacetate Cu(TFA)₂ under mild conditions is reported. The isolation of a molecular species during the course of this reaction, established as [Cu₂(TFA)₂(^tBu₂Se)₃], by spectroscopic studies and single crystal X-ray structure analysis, confirmed that metal selenide NPs are formed via this intermediate species containing a reduced copper center. Extending this reaction in the presence of commercial TiO₂ (P25) offered an easy synthesis of copper selenide–titania nanocomposites with different Cu/Ti ratios. These nanocomposites, well-characterized by powder XRD, STEM, TEM, BET, XPS, EDX and UV-Vis studies, were examined as photocatalysts for the degradation of formic acid (FA). The nCu_2−xSe–TiO₂ nanocomposites with low mol% of copper selenide, i.e. n = 0.1 and 0.3 mol%, displayed a superior catalytic activity over P25, which is an established benchmark for photocatalysis under UV light.