MOF-Derived Bi₂WO₆/MXene Ternary Heterojunction as a Highly Efficient Piezocatalyst for Ultrasound-Driven Hydrogen...

A Bi-MOF (CAU-17)-derived, Bi-rich Bi₂WO₆ composite (MBW0.25) is rationally designed and integrated with Ti₂C MXene to realize an efficient piezo-catalyst for ultrasound-driven hydrogen evolution and piezo-catalytic water splitting. Controlled Na₂WO₄ incorporation induces a dual-phase Bi₂WO₆/Bi_3.84W_0.16O_6.24 structure with lattice distortion and enhanced polarization, while partially retaining MOF domains. The resulting disordered Bi₂WO₆ framework exhibits distinct structural and electronic features compared to conventionally synthesized Bi₂WO₆, 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, Bi₂WO₆, and Ti₂C, 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.