Enhanced dark adsorption and visible-light-driven photocatalytic properties of narrower-band-gap Cu2S decorated Cu2O nanocomposites for efficient removal of organic pollutants.

• Cu 2 O/Cu 2 S nanocomposite was obtained by a co-precipitation and calcination method. • The decoration of Cu 2 S enhanced the adsorption and photocatalytic performances. • The recombination of photogenerated electrons and holes was suppressed effectively. • O 2 − and h + were crucial for the photocatalytic degradation of organic pollutants. The Cu 2 S-decorated Cu 2 O nanocomposites were synthesized by a facile co-precipitation and calcination method, and used as adsorbent and photocatalyst to remove organic pollutants from wastewater. Batch adsorption experiments were conducted to investigate the influences of molar ratio of Cu 2 O to Cu 2 S, initial solution pH, coexisting anion and temperature on the adsorption performances. As-obtained Cu 2 O/Cu 2 S-9/1 nanocomposite with high specific surface area (45.88 m2/g) exhibited superior adsorption ability towards Congo red, methyl orange and tetracycline in aqueous solution. The adsorption of organics onto the nanocomposite was a spontaneous and exothermic process, and the adsorption processes could be well described by the Freundlich isothermic and Pseudo-second-order kinetic models. The Cu 2 O/Cu 2 S-9/1 nanocomposite also showed excellent photocatalytic degradation activities for organic pollutants. Optical properties characterization suggested that the decoration of Cu 2 S could effectively enhance visible-light absorption and inhibit the recombination of photo-generated electron-hole pairs. ESR tests and trapping experiments of reactive species indicated that both superoxide radicals (O 2 −) and holes (h +) were crucial for the photocatalytic degradation of organic pollutants. Moreover, the photocatalytic efficiency of Cu 2 O/Cu 2 S-9/1 nanocomposite had no significant decrease even after four consecutive runs. The bifunctional nanocomposite as adsorbent and photocatalyst presents a great potential in treating organic-contaminated wastewater. [ABSTRACT FROM AUTHOR]