Interconnected ZnO@ZnS core–shell nanostructures for efficient piezocatalytic nitrogen fixation and dye degradation

Converting N 2 into ammonia under ambient conditions using mechanical energy-driven piezocatalysis represents a promising approach for sustainable nitrogen fixation, although its efficiency is often limited by insufficient nitrogen activation and rapid recombination of piezo-induced charge carriers. Herein, bi-piezoelectric ZnO-ZnS heterostructures were successfully constructed through a post-synthetic anion exchange strategy using electrospun ZnO as the precursor. The gradual O 2– to S 2- exchange process generated a core–shell structure composed of a ZnO core and a porous ZnS shell while preserving favorable interfacial coupling between the two piezoelectric phases. The optimized heterostructure achieved significantly enhanced ammonia production, delivering yields 2.1 and 8.9 times higher than those of ZnO and ZnS, respectively, and 2.5 times higher than a physical mixture of ZnO and ZnS with similar composition. This enhancement was also observed in dye degradation, demonstrating the general applicability of the heterostructure design. Mechanistic studies revealed that the improved performance originates from enhanced piezoelectric polarization, more efficient spatial charge separation, and abundant surface active sites that promote N 2 adsorption and activation. This work provides an effective strategy for constructing strongly coupled bi-piezoelectric heterostructures and highlights the importance of interface engineering for efficient piezocatalytic nitrogen fixation.