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 (similar to 1.4 eV bandgap) nanoparticles on ZnO (similar to 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/C-0 = 18.6% after eight cycles, while bare ZnO nanowires exhibited poorer performance (C/C-0 = 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.