Constructing Type-II and S‑Scheme Heterojunctions of Cu2O@Cu4(SO4)(OH)6·H2O Polyhedra by In Situ Etching Cu2O with Different Exposed Facets for Enhanced Photocatalytic Sterilization and Degradation Performance

• Published in: Inorganic chemistry Vol. 62; no. 23; pp. 9259 - 9271
• Main Authors: Du, Jin, Hu, Yongjian, Wan, Xia, Tie, Shaolong, Lan, Sheng, Gao, Xingsen
• Format: Journal Article
• Language: English
• Published: American Chemical Society 12.06.2023
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.3c01220

The construction of type-II or S-scheme heterojunctions can effectively accelerate the directional migration of charge carriers and inhibit the recombination of electron–hole pairs to improve the catalytic performance of the composite catalyst; therefore, the construction and formation mechanism of a heterojunction are worth further investigation. Herein, Cu2O@Cu4(SO4)­(OH)6·H2O core–shell polyhedral heterojunctions were fabricated via in situ etching Cu2O with octahedral, cuboctahedral, and cubic shapes by sodium thiosulfate (Na2S2O3). Cu2O@Cu4(SO4)­(OH)6·H2O polyhedral heterojunctions demonstrated obviously enhanced sterilization and degradation performance than the corresponding single Cu2O polyhedra and Cu4(SO4)­(OH)6·H2O. When Cu2O with a different morphology contacts with Cu4(SO4)­(OH)6·H2O, a built-in electric field is established at the interface due to the difference in Fermi level (E f); meanwhile, the direction of band bending and the band alignment are determined. These lead to the different migration pathways of electrons and holes, and thereby, a type-II or S-scheme heterojunction is constructed. The results showed that octahedral o-Cu2O@Cu4(SO4)­(OH)6·H2O is an S-scheme heterojunction; however, cuboctahedral co-Cu2O@Cu4(SO4)­(OH)6·H2O and cubic c-Cu2O@Cu4(SO4)­(OH)6·H2O are type-II heterojunctions. By means of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), diffuse reflectance spectra (DRS), and Mott–Schottky analyses, the band alignments, Fermi levels, and band offsets (ΔE CB, ΔE VB) of Cu2O@Cu4(SO4)­(OH)6·H2O polyhedral heterojunctions were estimated; the results indicated that the catalytic ability of the composite catalyst is determined by the type of heterojunction and the sizes of band offsets. Cubic c-Cu2O@Cu4(SO4)­(OH)6·H2O has the strongest driving force (namely, biggest band offsets) to accelerate charge migration and effectively separate charge carriers, so it exhibits the strongest catalytic bactericidal and degrading abilities.