Synthesis And Photocatalytic Performance Of Cu₂O Polyhedra/TiO₂ Composite Semiconductor

As a common semiconductor,Cu₂O has narrow band gap,reasonable cost,low toxicity,good environmental acceptability,and strong adsorption of molecular oxygen.These advantages have contributed to the application of C u2 O in the visible light photocatalytic degradation of organic pollutants.In this thesis,C u2 O polyhedra were synthesized at room temperature by the reduction of C u?OH?2 with NH₂OH·HCl.Three different morphologies of C u2 O polyhedra were obtained via simple adjustment of the amounts of NaOH.The optical properties,photocatalytic degradation of MO,growth processes,and catalytic properties of C u2 O polyhedra were investigated and analyzed.Then C u2O-O/TiO₂-QD heterojunctions were formed on the surface of Cu₂O-O by the precipitation of TiO₂-QDs sol in the presence of absolute ethanol.The optical properties,stability,structural advantages,and enhancement mechanism of Cu₂O-O/TiO₂-QD were investigated.In the synthesis of Cu₂O polyhedra,SDS was employed as a capping agent.Simple adjustment of molar ratio of N H₂OH·HCl to NaOH at 0.47-2.3 enabled C u2 O with exposed facet evolution from {1 0 0} to {1 1 0}.Cu₂O-C,Cu₂O-O,Cu₂O-R crystals with sizes of 0.31 ?m,2 ?m,1.5 ?m were synthesized with the introduction of 7.5 mL,2.7 mL,1.5 mL of NaOH.C u2O-C had six lower-energy facets of {1 0 0},Cu₂O-R had twelve higher-energy facets of {1 1 0},and C u2O-O had six lower-energy facets of {1 0 0} and twelve higher-energy facets of {1 1 0}.The light absorption of C u2 O polyhedra followed the order as C u2O-R > Cu₂O-O > Cu₂O-C,however,the photocatalytic degradation of MO by C u2 O polyhedra followed the order as Cu₂O-O > Cu₂O-R > Cu₂O-C.The photocatalytic activity of C u2O-O was 1.31 times and 2.21 times higher than that of Cu₂O-R and Cu₂O-C,respectively.Cu₂O-O/TiO₂-QD-?a?synthesized with 72 ?L of TiO₂-QDs sol exhibited a slight enhancement in the separation efficiency of electron-hole pairs and photocatalytic efficiency of MO.When 1.8 mL of TiO₂-QDs sol was added in preparation of Cu₂O-O/TiO₂-QD-?b?,it resulted in a core-shell structure and an obvious decrease in photocatalytic activity because Cu₂O-O could not effectively contact with the aqueous solution.However,when 360 ?L of TiO₂-QDs sol was added in preparation of Cu₂O-O/TiO₂-QD heterojunctions,highly dispersed TiO₂-QDs were partially loaded on C u2O-O.The C u2O-O/TiO₂-QD heterojunctions exhibited good dispersibility,good stability,and strong absorbance of visible light.The degradation rate of MO under visible light irradiation was 5.5 times higher than that of the Cu₂O-O.The enhanced visible light photocatalytic activity and good stability were attributed to effective separation of photoexcited electron-hole pairs and instant scavenging of holes in the unique heterojunction structure.