Constructing of CoP-Nb₂O₅ p-n heterojunction with built-in electric field to accelerate the charge migration in...

Studying interfacial charge transfer is of great significance for the preparation of electrocatalysts with high activity for the hydrogen evolution reaction (HER). Particularly, exploring the in-depth catalytic mechanisms and facile fabrication methods of narrow bandgap metal phosphides remains worthwhile. This work successfully combined catalytically inert n-type Nb₂O₅ with p-type CoP to prepare a p-n heterojunction (CoP-Nb₂O₅). The self-supporting heterojunction was fabricated by gas-phase phosphorization of the Co(OH)₂-Nb₂O₅ precursor obtained through hydrothermal-electrodeposition strategy. By analyzing the electronic and band structures of CoP and Nb₂O₅, it was found that there exists a built-in electric field (BEF) in the heterojunction. This BEF can modulate the electronic structure of CoP at the interface, enhance its intrinsic activity and accelerate charge migration. The subsequent experimental results also demonstrate that Nb₂O₅ can significantly enhance the activity and stability of CoP. Our findings can serve as a novel perspective on the application of p-n heterojunction in the field of energy storage and conversion.