Z-scheme ZnO@PDA/CeO2 heterojunctions using polydopamine as electron transfer layer for enhanced photoelectrochemical H2 generation

In this study, polydopamine (PDA)-bridged ZnO@PDA/CeO2 Z-scheme heterojunctions are rationally designed using PDA as an electron transfer mediator for an efficient photoelectrochemical water splitting under visible LED illumination. PDA-bridged construction not only provided the completely wrapping of ZnO nanoparticles (NPs) but also provided a biomimetic electron transfer layer with well-defined core-shell morphologies. Thanks to this novel Z-scheme heterostructure, an improved photocurrent density is recorded for ZnO@PDA/CeO2 photoanodes (251 μA/cm2 at 0.25 V vs. reversible hydrogen electrode [RHE]) under LED irradiation (30 mW/cm2), whereas a quite low photocurrent density (24 μA/cm2 at 0.25 V vs. RHE) is obtained in dark due to low separation of electron–hole pairs. Our results suggest that the presence of PDA provided a solid–solid interfacial interaction (between semiconductors: ZnO and CeO2) that facilitated the separation and pumping of photogenerated charge carries for enhanced photoelectrochemical water splitting. The Z-scheme charge transfer mechanism is verified using radical scavengers, radical trapping experiments, as well as X-ray photoelectron spectroscopy methods. This three-dimensional (3D) Z-scheme ternary heterostructures delivers a new insight in next generation of photocatalysts for efficient large-scale conversion of solar energy to H2 fuels as well as renewable energy revolution. [Display omitted] •Z-scheme ZnO@PDA/CeO2 heterojunctions were rationally designed using PDA.•PDA used as electron transfer layer with well-defined core-shell morphology.•Superior PEC performance was recorded: 251 μA/cm2 under 30 mW/cm2 LED intensity.•PDA-assisted interfacial interaction facilitated separation/pumping of e− and h+.•Z-scheme charge transfer was verified using radical trapping experiments and XPS.