Facile assembly of nanosheet array-like CuMgAl-layered double hydroxide/rGO nanohybrids for highly efficient reduction of 4-nitrophenol

A series of novel hierarchical nanosheet array-like hybrids xCu-LDH/rGO (xCu-LDH: CuxMg3-xAl-layered double hydroxide (x = 0.5, 1.0, and 1.5), rGO: reduced graphene oxide) were assembled via a facile and green aqueous-phase coprecipitation method. Systematic characterization suggests that the hybrids were constructed by hexagonal LDH nanoplates (similar to 70 nm x 4.5 nm) interdigitated vertical to the surface of single-layer rGO. All the xCu-LDH/rGO hybrids exhibit a remarkable higher activity for catalytic reduction of 4-nitrophenol (4-NP) compared with pure Cu-LDH, commercial Pt/C and other recently reported Cu-related catalysts. These findings were carefully explained by deep study of the catalyst treated with NaBH4, and the xCu-LDH/rGO hybrids as a potential Cu2O reservoir were revealed for the first time. Typically for 1.0Cu-LDH/rGO, a part of Cu2+ ions on LDH layers were instantaneously in situ reduced to well-dispersed ultrafine Cu2O nanoparticles (similar to 6.8 nm) by NaBH4 in an aqueous reduction system and thus formed relatively strong interaction between Cu2O and LDH/rGO greatly favoring enhanced activity for the reduction of 4-NP, other nitroarenes and organic dyes at room temperature. The excellent activity of the xCu-LDH/rGO hybrids can be attributed to the possible Cu2O-Cu-LDH-rGO three-phase synergistic effect, increased adsorption capacity for reactants via p-p stacking, and unique nanoarray-like morphology of the hybrids. Moreover, the 1.0Cu-LDH/rGO can be cycled for 20 runs without significant loss of activity, giving the hybrid long-term stability.