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 H 2 using photoelectrochemical (PEC) cell. The ternary heterojunction photoanode is constructed by modifying ZnO NRAs with ZnFe 2 O 4 nanosheets (NSs) and CdS nanoparticles (NPs), successively. The band alignment study demonstrates that ZnFe 2 O 4 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 ZnFe 2 O 4 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 H 2 generation rate of 92.9 μmol/h, 6.23 and 2.97 times of ZnO NRAs and ZnO/ZnFe 2 O 4 NRAs/NSs photoanodes, respectively.