Piezoelectric polarization accelerated charge separation in Zinc stannate based Schottky barrier for high-efficiency hydrogen evolution

Abstract

Piezoelectric polarization can effectively improve the separation and transfer of the carriers in photocatalyst. Herein, a dimension-matched piezo-photocatalyst was designed based on plate-like orthorhombic perovskite Zinc stannate (ZnSnO3)@reduced graphene oxide (rGO), which verified the prominent hydrogen (H2) evolution performance. Driven by the mechanical vibration induced piezoelectric field, the limitation of photocatalytic H2 evolution on the proper band edge position had been breached. The band of ZnSnO3 could be tilted more negative than H2O/H2 redox potential under the piezoelectric field, making it possible to achieve H2 evolution which was originally unsatisfactory. Moreover, on the basis of piezoelectric field, the Schottky barriers established in the catalyst further accelerated the electron separation. The electron paramagnetic resonance results demonstrated that the strongest ·O2− and ·OH radical intensities could only be observed when under the synergistic of light and ultrasonic. The effect of contents, size, surface chemistry of rGO and the ultrasonic power on piezo-photocatalytic performance were also optimized. Satisfactory, the ZnSnO3@rGO exhibited superior piezo-photocatalytic H2 evolution (5.66 mmol g−1), which was four times more than that of ZnSnO3 (1.37 mmol g−1). This work sheds light on the essentially synergistic effect of the mechanical and luminous energy in H2 evolution through piezo-phototronic process.