MOF‐Derived Bi ₂ WO ₆ /MXene Ternary Heterojunction as a Highly Efficient Piezocatalyst for Ultrasound‐Driven Hydrogen Evolution and Oxygen Evolution Reaction

ABSTRACT A Bi‐MOF (CAU‐17)‐derived, Bi‐rich Bi ₂ WO ₆ composite (MBW0.25) is rationally designed and integrated with Ti ₂ C MXene to realize an efficient piezo‐catalyst for ultrasound‐driven hydrogen evolution and piezo‐catalytic water splitting. Controlled Na ₂ WO ₄ incorporation induces a dual‐phase Bi ₂ WO ₆ /Bi _3.84 W _0.16 O _6.24 structure with lattice distortion and enhanced polarization, while partially retaining MOF domains. The resulting disordered Bi ₂ WO ₆ framework exhibits distinct structural and electronic features compared to conventionally synthesized Bi ₂ WO ₆ , favoring piezo‐induced charge separation. Coupling MBW0.25 with 5 wt.% MXene yields an unprecedented MOF‐derived oxide/MXene ternary heterojunction for piezo‐catalysis with excellent efficiency. The optimized MBW0.25/MX‐5 achieves a high piezo‐hydrogen evolution rate of 1450.1 µmol g ⁻¹ h ⁻¹ , representing ∼36, ∼21, and ∼7‐fold enhancements over pristine Bi‐MOF, Bi ₂ WO ₆ , and Ti ₂ C, respectively. Radical trapping experiments reveal a non‐conventional •OH‐mediated hydrogen evolution pathway, distinguishing this system from typical electron‐driven piezocatalytic processes. The catalyst maintains relatively stable activity in tap water and shows appreciable performance in seawater. Piezo‐electrochemical oxygen evolution reaction measurements further confirm efficient mechanical‐to‐electrical energy conversion, evidenced by reduced overpotentials, increased piezo‐currents, and lowered charge‐transfer resistance under vibration.