ZnFe2O4 Dendrite/SnO2 Helix 3D Hetero‐Structure Photoanodes for Enhanced Photoelectrochemical Water Splitting: Triple Functions of SnO2 Nanohelix

An array of SnO₂ nanohelix structures is employed to fabricate a SnO₂ helix@ZnFe₂ O₄ dendrite core-shell 3D heterostructure photoanode for photoelectrochemical (PEC) water splitting. The SnO₂ helix provides triple critical functions to enhance the PEC performance of the photoanode. First, it scatters the incident light to achieve a higher light harvesting efficiency. Second, it provides a facile electron pathway as an electron transfer layer (ETL) while blocking hole transport to mitigate charge recombination in the bulk of ZnFe₂ O₄ . Finally, it becomes a template for the formation of ZnFe₂ O₄ dendrite nanostructure shell. The ZnFe₂ O₄ dendrite/SnO₂ helix photoanode exhibits a remarkable increase in incident photon-to-electron conversion efficiency compared to unmodified ZnFe₂ O₄ with no ETL and modified one with "flat" SnO₂ ETL. The surface of the ZnFe₂ O₄ /SnO₂ helix photoanode is further modified with TiO₂ passivation layer and NiFeO_x oxygen evolution co-catalyst to achieve one of the best PEC performances among reported ZnFe₂ O₄ -based photoanodes.