Embedding Plasmonic NbN into Sandwiched Metal/Semiconductor Heterostructures for Enhanced Hot-Electron-Driven Photocatalytic Water Splitting

In plasmonic metal/semiconductor heterostructures, light-matter interactions that induce charge and energy transfer across the metal–semiconductor interface form the foundation for plasmon-enhanced light energy conversion processes such as photocatalysis. One determining factor in hot electron extraction efficiency is the configuration of the heterostructure, including the geometry and positioning of plasmonic nanostructures relative to the semiconductor. Here, with plasmonic niobium nitride (NbN) as a model system, we showcase an innovative strategy to create a three-dimensional embedded plasmonic metal/semiconductor heterostructure between NbN and its native oxide semiconductor─Nb2O5. This Nb2O5/NbN/Nb2O5 heterostructure efficiently harnesses the plasmon resonance of NbN in the visible to near-infrared region to generate energetic hot carriers, which are then effectively transferred from plasmonic NbN to the conduction band of Nb2O5. The embedded heterostructure achieves a hydrogen production rate of 181 μmol/g/h in photocatalytic water splitting under AM 1.5G solar irradiation, nine times higher than that of the nonembedded heterostructure. Photoelectrocatalytic results further demonstrate that the large photocurrent observed for the embedded heterostructure is primarily attributed to the hot-electron transfer mechanism, confirming the enhanced hot-electron extraction efficiency due to the relief of interfacial momentum conservation constraints.