Interfacial charge separation and transfer are the main challenges of efficient semiconductor-based Z-scheme photocatalytic systems. Here, it is discovered that a Schottky junction at the interface between the BiVO 4 {010} facet and Au is an efficient electron-transfer route useful for constructing a high-performance BiVO 4 {010}-Au-Cu 2 O Z-scheme photocatalyst. Spectroscopic and computational studies reveal that hot electrons in BiVO 4 {010} more easily cross the Schottky barrier to expedite the migration from BiVO 4 {010} to Au and are subsequently captured by the excited holes in Cu 2 O. This crystal-facet-dependent electron shuttle allows the long-lived holes and electrons to stay in the valence band of BiVO 4 and conduction band of Cu 2 O, respectively, contributing to improved light-driven CO 2 reduction. This unique semiconductor crystal-facet sandwich structure will provide an innovative strategy for rational design of advanced Z-scheme photocatalysts.

Gaseous oxides generated during industrial processes, such as carbon oxides (CO x ) and nitrogen oxides (NO x ), have important effects on the Earth’s atmosphere. It is highly desired to develop a low-cost and efficient route to convert them to harmless products. Here, direct splitting of gaseous oxides was proposed on the basis of photocatalysis by an amorphous oxide semiconductor. As an example, splitting of CO2 into carbon and oxygen was achieved over amorphous zinc germanate (α-Zn-Ge-O) semiconductor photocatalyst under 300 W Xe lamp irradiation. Electron paramagnetic resonance and 18O isotope labeling indicated that the splitting of CO2 was achieved via photoinduced oxygen vacancies on α-Zn-Ge-O reacting and thus filling with O of CO2, while the photogenerated electrons reduced the carbon species of CO2 to solid carbon. Under irradiation, such a defect reaction is sustainable by continuous photogenerated hole oxidation of surface oxygen atoms on α-Zn-Ge-O to form oxygen vacancies and to release O2. When we used H2O or NO in place of CO2, H2 and O2 or N2 and O2 were evolved, respectively, indicating the same mechanism can also split H2O or NO.

The product selection for CO2 reduction depends on the surface chemistry of Ta3N5 and LaTiO2N photocatalyst.