Mechanism Insight into an Unprecedented Dual Series-Parallel Photocharge Separation in Quaternary Cu2O Facet Junctions

Uncovering the contribution of anisotropic crystal facets in single-crystalline photocatalysts is still a challenge in fundamental study. Here, the mechanism underlying facet junction-dependent photocharge separation in polyhedral Cu2O is demonstrated, which is beneficial for understanding why 50-faceted Cu2O exhibiting quaternary {100}/{110}/{111}/{522} facet junction possesses an enhanced photodegradation activity toward tetracycline than that of the 26-faceted Cu2O exhibiting ternary {100}/{110}/{111} and 18-faceted Cu2O exhibiting binary {100}/{110} facet junction. Density functional theory (DFT) calculations and selective photodeposition results confirm that hierarchical facet junctions are formed in a 50-faceted Cu2O, which could be regarded as one parallel connection between binary {110}/{111} and ternary {110}/{522}/{100} series facet junction for conduction band minimum, and another parallel connection between binary {100}/{522} and ternary {111}/{110}/{522} series facet junction for valence band maximum, leading to an unprecedented dual series-parallel transfer pathway for more efficiently improved photocharge separation. Hopefully, this study would be a beneficial guideline for scientific researchers currently concentrating on the facet junction engineering of polyhedral photocatalysts.