Enhanced charge separation at coherent semiconductor/substrate Interface in oxygen vacancy-enriched ZnO Nanorods decorated SnO2 inverse opal skeletons Photoanode

Issues of charges transfer at the SSI interface have been studied in depth. • The carrier separation efficiency was improved by introduce SnO 2 at SSI interface. • Coherent boundary at SSI can strikingly reducing the charge transfer resistance. • Ov-ZnO provide enough active sites for the OER beneficial to the mass transfer. • An excellent stable photocurrent density of 1.13 mA cm −2 is generated at 1.2 V. Efficient extraction of photogenerated electrons across the semiconductor/conductive-substrate interface is essential for photoelectrochemical (PEC) water oxidation, yet this interface is often less considered than bulk and surface charge-transfer processes. Herein, oxygen-vacancy-enriched ZnO nanorods (Ov-ZnO NRs) were grown on three-dimensionally ordered SnO 2 inverse-opal skeletons to construct a hierarchical SnO 2 IOs/Ov-ZnO photoanode. The interconnected SnO 2 inverse opal simultaneously provides a conductive framework and enhances light harvesting through multiple scattering and slow-photon effects, while its crystallographic compatibility with the FTO substrate alleviates electron-transfer losses at the semiconductor/substrate interface. The one-dimensional Ov-ZnO NRs provide short carrier-transport pathways, a large electrode/electrolyte contact area, and defect-mediated active sites for water oxidation. The optimized photoanode delivered a photocurrent density of 1.13 mA cm −2 at 1.2 V vs. RHE, approximately 3.3 times that of the flat SnO 2 /ZnO NRs reference (0.34 mA cm −2 ), together with an applied-bias photon-to-current efficiency of 0.274% at 0.80 V vs. RHE. Its bulk charge-separation and surface charge-injection efficiencies reached 53.3% and 71%, respectively, at 1.2 V vs. RHE. Spectroscopic, electrochemical, and density functional theory analyses collectively indicate enhanced interfacial charge redistribution, lower charge-transfer resistance, and more favorable OER energetics. These results establish the coordinated engineering of the conductive substrate interface, photonic architecture, and oxygen-vacancy defects as an effective strategy for improving ZnO-based PEC photoanodes. Download: Download high-res image (215KB) Download: Download full-size image