Asymmetric Single‐Unit‐Cell Layer Enriching Polar Inherent Hydroxyls Eliminates Interlayer Electric Field Shielding Effect and In Situ Self‐Polarize for Piezocatalytic Water Splitting

Abstract

AbstractPiezocatalytic two‐electron water splitting into spontaneously isolated H2 and H2O2 shows huge prospects in meeting industrial requirements. Herein, asymmetric single‐unit‐cell Bi2O2(OH)(NO3) monolayer (BON‐M) with superb force‐sensitivity are developed for pure water and seawater dissociation. The formation of a monolayer structure allows sufficient exposure of polar inherent hydroxyls and eliminates the interlayer electric field screening induced by hydrogen bonding between [Bi2O2OH] slices and [NO3] layers, resulting in larger piezoelectricity and strengthened internal electric field. It also benefits surface charge carrier decoupling and renders more favorable H2O molecules adsorption and H* desorption. Particularly, the mechanical strain can induce the in situ self‐polarization of BON‐M, which further enhances electric field intensity and reduces energy barriers of H* desorption and key intermediate *OH formation, facilitating water splitting to H2 and H2O2 kinetically and thermodynamically. An exceptional piezocatalytic H2 and H2O2 production rate up to 2071.05 and 970.27 µmol g−1 h−1 is delivered by BON‐M from pure water. It also accumulates H2 output of 12 429.68 µmol g−1 within 8 h from seawater splitting, along with mechanical‐to‐hydrogen efficiency of 0.15%. This work develops an effective strategy for exploiting high‐performance piezocatalyst by building ultrafine nanostructure enriched with inherent polar groups on the surface.