Surface Plasmon Effect of Cu and Presence of n–p Heterojunction in Oxide Nanocomposites for Visible Light Photocatalysis

Abstract

In this paper, we report the design, synthesis, and characterization of three different composite nanomaterials (Cu-ZnO, Cu-Cu₂O-ZnO, and Cu₂O-ZnO) with surface plasmon resonance (SPR) effect and n–p heterojunction for visible light photocatalysis. We have accounted for the first time the SPR effect of Cu in photocatalysis for promotion of efficient electron–hole separation that further enhances visible light induced photocatalytic activity. To make the composite efficient we have judiciously introduced cheap and common Cu and Cu₂O in ZnO matrix individually and cojointly to make the composites visible light sensitizer. Furthermore, wide band gap barrier of ZnO crosses its UV limit in the composites and spreads over to visible region. By simply varying the complexing agents, here we achieve success to obtain three kinds of highly stable composite nanomaterials with three distinct structures from identical experimental condition. This synthetic strategy offers a radically different approach where oxidation of Cu is inhibited in the matrix and visible light induced photocatalytic performance remains unaltered for months. Interestingly, the combined effect of both Cu and Cu₂O in the as-synthesized ternary composite, Cu-Cu₂O-ZnO endorses highest photocatalytic activity than the other two composites. This activity attributed to extended light absorption, effective transfer of photogenerated carriers and presence of strong SPR effect. Finally, the comparative photocatalytic activity of all the nanocomposites has been accounted from methylene blue (MB) degradation in aqueous solution under visible light irradiation