Spinodal decomposition enables coherent plasmonic metal/semiconductor heterostructure for full spectrum photocatalysis

Nanoscale metal/semiconductor heterostructures are critical components for a variety of light energy conversion applications. Herein, with plasmonic hafnium nitride (HfN) as a model system, we show that spinodal decomposition can be exploited as a unique means to produce the lattice-coherent metal/semiconductor heterostructure between HfN and its native oxynitride semiconductor-Hf₂ON₂. Atomic-resolution electron microscopy imaging provides direct visualization of the complete lattice coherency over the interface region with precisely controlled spatial modulation. The light-harvesting HfN component exhibits a broadband plasmonic absorption covering visible and near-infrared regions, and the plasmonically excited hot electrons can be efficiently injected into neighboring Hf₂ON₂ across interface. When combined with a small amount of Pt co-catalyst, the coherent HfN/Hf₂ON₂ heterostructure achieves high-efficiency photocatalytic H₂ production from methanol decomposition under visible and NIR light illumination, with apparent quantum yields of 27% at 600 nm and 13.9% at 850 nm, respectively. This performance contributes to the efficient utilization of a broad solar spectrum in photocatalysis and solar energy conversion applications.