Versatile ultrasound-induced piezoelectric deposition of metals on ZnO nanostructures for hybrid electrocatalysts

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Hybrid metal–semiconductor nanostructures represent key platforms for electrocatalysis. However, their synthesis often requires multistep procedures and chemical reducing agents. Here we report a reductant-free strategy for the synthesis of ZnO@noble metal hybrids based on ultrasound-induced piezoelectric deposition. Under ultrasonic irradiation, the mechanical deformation of piezoelectric ZnO generates transient electric fields that promote the direct reduction of metal ions at the oxide interface, enabling the one-step formation of ZnO@M structures (M = Ag, Au, Pd, Pt). Structural and spectroscopic characterization confirms the formation of highly dispersed metal nanoparticles and reveals metal-dependent interactions with the ZnO support. While Ag and Au remain weakly coupled to the oxide surface, Pd and Pt form strongly polarized M−O−Zn interfacial domains that significantly modify the electronic properties of the ZnO nanostructures. These interfacial effects led to enhanced electrocatalytic activity. In particular, ZnO@Pd and ZnO@Pt show improved oxygen reduction reaction performance, while ZnO@Pt exhibits outstanding hydrogen evolution activity despite the very low metal loading, reaching 10 mA cm−2 at only 60 mV overpotential. Remarkably, under the same experimental conditions ZnO@Pt surpasses a Pt/C benchmark (20 wt% Pt), achieving lower overpotential (60 vs 70 mV at 10 mA cm−2) and a steeper Tafel slope (42 vs 69 mV dec-1) while employing over twenty times less Pt, which highlights the exceptional efficiency of the engineered Pt-O-Zn interface. Photoexcitation of ZnO further enhances the catalytic response. This work demonstrates that ultrasound-driven piezochemical deposition provides a versatile and sustainable route for engineering efficient metal–semiconductor catalytic interfaces.