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.

中文翻译：

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通过原位蚀刻具有不同暴露面的 Cu2O 构建 Cu2O@Cu4(SO4)(OH)6·H2O 多面体的 II 型和 S 型异质结，以增强光催化杀菌和降解性能

II型或S型异质结的构建可有效加速载流子的定向迁移，抑制电子-空穴对的复合，提高复合催化剂的催化性能；因此，异质结的构建和形成机制值得进一步研究。_在此，采用硫代硫酸钠_（Na 2 _{S 2} _ _ _{_} _ _{_} O ₃）。Cu ₂ O@Cu ₄ (SO₄ )(OH) ₆ ·H ₂ O多面体异质结比相应的单一Cu ₂ O多面体和Cu ₄ (SO ₄ )(OH) ₆ ·H ₂ O具有明显增强的杀菌和降解性能。当Cu ₂ O与不同的形貌与Cu ₄ (SO ₄ )(OH) ₆ ·H _{2 O接触，由于费米能级(} E _{f )}的差异在界面处建立了内建电场); 同时，确定了带弯曲的方向和带排列。这些导致电子和空穴的不同迁移路径，从而构建II型​​或S型异质结。结果表明，八面体o-Cu ₂ O@Cu ₄ (SO ₄ )(OH) ₆ ·H ₂ O为S型异质结；然而，立方八面体co-Cu ₂ O@Cu ₄ (SO ₄ )(OH) ₆ ·H ₂ O和立方c-Cu ₂ O@Cu ₄ (SO ₄ )(OH) ₆ ·H ₂O是II型异质结。通过 X 射线光电子能谱 (XPS)、紫外光电子能谱 (UPS)、漫反射光谱 (DRS) 和 Mott–Schottky 分析，能带排列、费米能级和能带偏移 (Δ E CB _, Δ E _VB )的Cu ₂ O@Cu ₄ (SO ₄ )(OH) ₆ ·H ₂ O多面体异质结被估计；结果表明，复合催化剂的催化能力取决于异质结的类型和带偏移的大小。立方c-Cu ₂ O@Cu ₄ (SO ₄ )(OH) ₆ ·H ₂O 具有最强的驱动力（即最大的带偏移）来加速电荷迁移并有效分离电荷载流子，因此它表现出最强的催化杀菌和降解能力。