Formation of Cu0 in Cu2O under light irradiation and subsequent accelerated decoloration to MO aqueous solution

In the photocatalytically decoloring process of methyl orange (MO) aqueous solution by Cu2O polycrystalline film, Cu+ was reduced to Cu0 and oxidized to Cu2+ simultaneously. The adsorption of MO molecules onto the Cu2O film was deduced by complexation reactions between Cu0 and the MO molecules, thus enhancing the decoloration rate of the aqueous solution. This research demonstrates that, apart from the photocatalytic activity of Cu2O, Cu0 plays an important role in the bleaching process of MO solution. The results also suggest the application of metallic copper as a candidate for treatment of textile dyeing wastewater.

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► In photocatalytically decoloring MO solution by Cu2O, Cu+ was reduced to Cu0.
► Complexation reaction between Cu0 and MO molecules enhanced decoloration rate.
► Decoloration was due to combined action of photocatalysis and complexation.
► Complexation reaction deduced formation of Cu2O.