Preparation And Properties Of Cu₂O And Its Composites

Cu₂O is a semiconductor with narrow band gap?E_g=2.17eV?,which is widely applied in photocatalysis,lithium ion batteries and sensors,etc.In recent years,the research on the preparation and properties of cuprous oxide has attracted wide interest among researchers.As a photocatalysis,the problem of rapid recombination of photogenerated carriers limited the application of Cu₂O,In this work,cuprous oxide with crystal face heterojunction and a composite material Cu₂O/Bi₂O₃ were prepared to inhabit the recombination of photogenerated carriers.The transport of photo-generated carrier were studied in the cuprous oxide crystal faces and the composites.The photocatalysis and adsorption properties were also studied.In this paper,Cu₂O was synthesized by solvent reduction method,and its morphological evolution in CuCl₂/NaOH/C₆H₁₂O₆ system was analyzed.The cuprous oxide polyhedron with different exposure degrees of?111??100?crystal plane were prepared by adjusting the concentration of Cu²⁺.With decreasing of face exposure ratio,the morphology of the cuprous oxide are truncated cube,cubic octahedron,truncated octahedron,and octahedron,respectively.With the increase of area of?111?crystal plane,the photocurrent density increases and then decreases.The photocatalytic performance of degradation of methyl orange are arranged in the order truncated octahedron>cubic octahedron>octahedron>truncated cube.Compared with the octahedron exposed only by the?111?crystal facet,the coexistence of?111??100?facets facilitate to the separation of the photogenerated electrons and the holes.The photo-generated holes in the?111?facet of Cu₂O migrate toward the?100?crystal facet,and the photogenerated electrons of the?100?crystal facet migrate toward the?111?crystal facey.A series of nanoparticles-assembled mesoporous Cu₂O/Bi₂O₃ composites were synthesized by wet chemical reduction method.By adjusting the molar ratio of Cu-Bi,the morphology of Cu₂O/Bi₂O₃ composites evolved from polyhedron to microsphere to irregular agglomerate.With the increasing of Bi₂O₃ content,the grain size of Cu₂O is gradually refined.The surface morphology of the composite material is continuously flocculated and loosened.The nanoparticles-assembled mesoporous composite have high specific surface area with positive potential,which drive the MO to diffuse and mass transfer and then adsorb on surface.The surface of the prepared composite material is positively charged,exhibiting selective adsorption to methyl orange and excellent adsorption performance.The maximum adsorption capacity can reach 1533.2mg/g.The separation performance of photogenerated carriers is greatly improved due to the composition of Cu₂O and Bi₂O₃.With the increasing of Bi₂O₃ content,the light absorption edge of Cu₂O/Bi₂O₃ composites is red-shifted,the band gap are narrowed.the light absorption intensity increases and then decreases,and the photocurrent density increases and then decreases.When the content of Bi₂O₃ is low,the interface area for forming a heterojunction is limited.When the content of Bi₂O₃is high,the Cu₂O is covered by Bi₂O₃ and the heterojunction is not exerted,which is not conducive to the transmission of photogenerated carriers.The changes of functional groups after adsorption and illumination of Cu₂O/Bi₂O₃ composites were characterized by FTIR.At the same time,the morphology of composite after adsorption of MO and photocatalytic post-treatment were observed.After the light treatment,the adsorbed MO is degraded by photocatalyisis.Thus,the composite material is considerable to adsorption cycle by photocatalytic regeneration and the methyl orange dye is efficiently and completely removed.