ZnFe2O4 nanosheets as an electron transport bridge and a hole mediator enhance solar-driven unbiased hydrogen generation of ZnO-based nanorod arrays photoanode

In this study, a novel ternary ZnO-based nanorod arrays (NRAs) photoanode is designed and constructed for the first time for unassisted solar-light-driven water splitting to generate H2 using photoelectrochemical (PEC) cell. The ternary heterojunction photoanode is constructed by modifying ZnO NRAs with ZnFe2O4 nanosheets (NSs) and CdS nanoparticles (NPs), successively. The band alignment study demonstrates that ZnFe2O4 NSs as an interfacial modification layer not only enlarge the contact area with ZnO and CdS respectively to build a stair-step band alignment of conduction band levels for the efficient transport of electrons but also make the valence band of ZnFe2O4 to be as the hole accumulation site in the ternary heterojunction. The electrochemical and photoluminescence measurements demonstrate the efficient separation of the carriers. Consequently, the ternary ZnO-based NRAs photoanode achieves a significant H2 generation rate of 92.9 μmol/h, 6.23 and 2.97 times of ZnO NRAs and ZnO/ZnFe2O4 NRAs/NSs photoanodes, respectively.