Enhanced catalytic performance by multi-field coupling in KNbO3 nanostructures: Piezo-photocatalytic and ferro-photoelectrochemical effects

The coupling between piezo-/ferroelectricity and photoexcitation in semiconductors creates unique opportunities to enhance the photocatalytic and photoelectrochemical (PEC) performance. It is important to develop desirable piezo-/ferroelectric nanostructures to realize the full potential of polarization-modulated built-in electric fields that can effectively separate excited electron/hole pairs. In this work, taking KNbO3 as a representative material, we show that two-dimensional nanosheets exhibit greatly improved piezo-photocatalytic degradation efficiency for organic dyes compared to that of nanocubes. In addition, effective tuning of the PEC water splitting property by manipulating the ferroelectric polarization was observed in these KNbO3 nanostructures, demonstrating versatile and tuneable devices for solar energy conversion. By changing the poling configuration, a significant photocurrent density enhancement of 55% was achieved for KNbO3 nanosheets, which is much greater than the 25% enhancement observed for the nanocube counterparts. These results could be attributed to the larger piezo-/ferroelectric response in the nanosheets as determined by piezoresponse force microscopy analysis and piezoelectric potential simulation based on the finite element method. Our findings may provide insights into strategies for designing highly efficient piezo-/ferroelectric nanomaterials for solar energy conversion.