Piezoelectric‐Photocatalytic S‐Scheme Heterojunction in Na─Sm Co‐Doped CaBi 2 Nb 2 O 9 @Mn─Cu─Ni─MOF for Enhanced Hydrogen Generation From Water Splitting

ABSTRACT Suppressing the recombination of photogenerated electrons and holes to achieve highly efficient energy conversion in an environmentally benign manner represents a pivotal challenge in green chemistry. In this work, we report on a novel composite that combines 2D piezoelectric Na─Sm co‐doped CaBi 2 Nb 2 O 9 (NSC) nanoplatelets with a Mn─Cu─Ni─metal‐organic framework (MOF) photocatalyst to create a piezoelectric@photocatalyst (NSC@MOF) heterojunction nanohybrid catalyst. This hybrid system demonstrates remarkable mechano‐driven photocatalytic hydrogen evolution efficiency (441.7 µmol g −1 h −1 ), significantly surpassing the performance of a standalone photocatalyst or piezo‐catalyst. Detailed experimental measurements and theoretical simulations elucidate the underlying catalytic mechanism, that is, the built‐in electric field generated by the piezoelectric NSC during mechanical stimulation inhibits the bulk recombination of photogenerated electron–hole pairs under illumination. Critically, the constructed covalent Mn─O─Sm bridge between the NSC and MOF breaks the high interfacial charge‐transfer barrier and establish a ‘charge transport superhighway’ for mechanically excited free carriers, and build an S‐scheme heterojunction at the NSC–MOF interface for enhanced interfacial charge transfer. The surface of the NSC@MOF exhibits significantly improved adsorption of H + from the solution, enabling efficient piezo‐photocatalytic water splitting. This work presents a novel green strategy for advancing sustainable energy conversion technologies using piezoelectric‐driven photocatalysis.