Constructing desired interfacial energy band alignment of Z-scheme TiO2-Pd-Cu2O hybrid by controlling the contact facet for improved photocatalytic performance

Interfacial energy band alignment determines the charges transfer path at the interface of semiconductor-based Z-scheme photocatalytic system. Herein, an elaborately designed TiO2-Pd-Cu2O Z-scheme hybrid, with desired energy band alignment for simultaneously facilitating electrons transfer from TiO2 to Pd and holes transfer from Cu2O to Pd, is achieved by controlling the TiO2{001} facet, Cu2O{100} facet and Pd as Photosystem II (PS II), Photosystem I (PS I) and electron mediator, respectively. The TiO2{001}-Pd-Cu2O{100} hybrid exhibits 1.37-3.12 times higher photocurrent density and 1.22-2.06 folds higher phenol degradation efficiency than other three hybrids with TiO2{101} facet or Cu2O(111) facet contacted with Pd at the interface. Density Function Theory (DFT) calculations reveal that the work functions are in order of TiO2{001} < Pd < Cu2O {100}, which facilitates both electrons transfer from TiO2{001} facet to Pd and holes transfer from Cu2O{100} facet to Pd, hence remains the high-energy electrons on Cu2O{100} facet and high-energy holes on TiO2(001} facet for efficient degradation of organic pollutants. This work gives an insight on rational construction of Z-scheme photocatalytic system depending on the energy band alignment of contact facets.