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.

Automated summary

The mechanism of facet junction-dependent photocharge separation in polyhedral Cu2O is demonstrated, and the impact of different facet junctions on photodegradation activity is compared. The results reveal that hierarchical facet junctions are formed in 50-faceted Cu2O, leading to more efficient photocharge separation.