Spatially Engineered Ternary Schottky/S-Scheme Heterojunctions for Artificial Photosynthesis.

Photocatalytic CO2 reduction into solar fuels presents a promising strategy for carbon mitigation and sustainable energy conversion. However, single-component photocatalysts suffer from inefficient charge separation, while binary heterojunctions-even with cocatalysts assistance-often undergo rapid Coulombic recombination due to timescale mismatches between ultrafast charge transfer and slower surface reaction kinetics. To overcome these limitations, a spatially engineered Nb2C/Nb2O5/ZnO ternary heterostructure is developed by anchoring ZnO quantum dots (QDs) onto Nb2O5 nanorods grown in situ from Nb2C MXene. This architecture integrates an Nb2O5/ZnO S-scheme heterojunction and an Nb2C/Nb2O5 Schottky junction, sharing Nb2O5 as a central mediator, thereby establishing bidirectional interfacial electric fields (IEFs) that direct photogenerated electrons toward ZnO and holes toward Nb2C. In situ irradiated X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), and femtosecond transient absorption spectroscopy (fs-TAS) reveal interface-specific electronic interactions and time-resolved carrier dynamics, confirming efficient and spatially resolved charge migration across the decoupled interfaces. This spatial charge separation effectively suppresses Coulombic recombination and prolongs carrier lifetimes. Additionally, the photothermal effect of Nb2C MXene enhances CO2 chemisorption and activation at defective ZnO QDs. These synergistic effects collectively enable high-efficiency CO2 photoreduction without molecular cocatalysts or sacrificial agents, providing a mechanistically distinct and scalable approach for artificial photosynthesis.