Balanced Excitation between Two Semiconductors in Bulk Heterojunction Z-Scheme System for Overall Water Splitting

Heterogeneous bilayered semiconductor thin films were fabricated using p -type CaFe 2 O 4 and n -type BiVO 4 for photocatalytic overall water splitting. The interface of the semiconductor layers was modified with Co 3 O 4 and a platinum co-catalyst. The resulting a bulk heterojunction film, which was composed of Co 3 O 4 /BiVO 4 /Pt/CaFe 2 O 4 /Pt and was fabricated on a substrate, produced both oxygen and hydrogen under visible-light irradiation in the absence of applied bias potential or sacrificial agents. Furthermore, a balanced absorbed photon number between CaFe 2 O 4 and BiVO 4 was shown to be a critical factor for achieving overall water splitting, thereby generating H 2 and O 2 molecules in a 2:1 stoichiometric ratio. These results demonstrate that the interfacial design and management of absorbed photon number in heterogeneous photocatalysts are essential factors for constructing Z-scheme systems that are capable of overall water splitting.