Piezotronic-effect-enhanced Ag₂S/ZnO photocatalyst for organic dye degradation

Taking advantage of the piezotronic effect, enhanced photocatalytic performance of a Ag₂S@ZnO hybrid photocatalyst was achieved under sonication. Decorating Ag₂S (∼1.4 eV bandgap) nanoparticles on ZnO (∼3.3 eV bandgap) nanowire surfaces successfully extended the light response to the visible light range. The formation of type II band alignment at the Ag₂S/ZnO heterointerface facilitated the separation of photoexcited electrons and holes, promoting utilization of photoexcited charge carriers in the photocatalytic process. Furthermore, the strain-generated positive piezocharges effectively lowered the barrier height, considerably motivating charge transport across the Ag₂S/ZnO heterointerface, which further boosted the hybrid photocatalyst performance. The high reproducibility of the photocatalytic activities indicated that the modification of ZnO nanowires with Ag₂S nanoparticles effectively stabilized the photocatalyst in reactions. The degradation rate of Ag₂S@ZnO nanowires remained at C/C₀ = 18.6% after eight cycles, while bare ZnO nanowires exhibited poorer performance (C/C₀ = 48.1%). This study showed the effectiveness of using the piezotronic effect in water purification and recovery by combined use of solar and mechanical energy.