Band edge alignment for tuning interfacial charge transfer: a case study of NaTaO3 as photoelectron platform by anchoring CdTe quantum dots

CdTe quantum dots (QDs) were anchored on NaTaO3 nanocubes with the aim into tuning the charge kinetics for spatial separation of the photogenerated electrons and holes by modifying the relative potential of the conduction band of CdTe QDs. In this work, CdTe QDs (particle size 2–3 nm) and NaTaO3 were synthesized via reflux and hydrothermal reaction. Thioglycolic acid (TGA) acted as both a stabilizer and linker molecules during the synthesis of CdTe QDs and NaTaO3/CdTe heterostructure. On accounts of density functional theory (DFT) predictions, electrons can transfer from NaTaO3 to CdTe due to the difference of the Fermi level between two semiconductors, which will establish a built-in electric field at semiconductor interfaces, accelerating the charge separation kinetics between CdTe and NaTaO3. In response, electronic structure tunable CdTe QDs were surface engineered on NaTaO3 nanocubes to enhance the visible light (VL) harvesting capability. By carefully controlling the fine nature of CdTe QDs, photogenerated electrons in CdTe can be efficiently injected into the conduction band of NaTaO3, leading to spatial charge separation between CdTe and NaTaO3. This could be affirmed by applied bias photo to current efficiency (ABPE), incident photocurrent responses as well as electrochemical impedance curves. With well-defined crystallinity, electronic structure, and interfacial contact between NaTaO3 and CdTe, the optimized photocatalytic activity toward hydrogen production over NaTaO3/CdTe heterostructure achieved an evolution rate of 56 μmol·g−1·h−1, which is far surpassed than that of pristine NaTaO3 and CdTe.