Efficient Charge Separation via MoSe2 Nanosheets with Tunable 1T Phase Contents: Piezoreduction of Cr(VI) to Cr(III) and Piezodegradation of RhB

Piezocatalysis is a promising technology to address environmental pollution by converting mechanical energy into chemical energy. Herein, MoSe2 nanosheets with different 1T phase percentages (ranging from 30 to 80%) were constructed by adjusting hydrothermal temperature. Moreover, the roles of phase engineering in the piezocatalysis were thoroughly investigated by degrading rhodamine B and reducing Cr(VI) in ultrasonic vibration conditions. In particular, MoSe2 prepared at 220 °C (MoSe2-220) exhibits ultrahigh observed constant kobs and degradation rate k, which is superior to most reported catalysts to date. The experimental results indicate that the introduction of the 1T phase increases the active sites of the material, improves the conductivity, and inhibits the recombination of electrons and holes. Moreover, an internal electric field in the 2H phase induced by piezoelectric polarization is facilitated to separate electron-hole pairs, enabling the degradation and reduction to proceed. The capture experiments and EPR tests further confirm that •O2- and •OH are main reactive species, and a rational mechanism is finally put forward. This study offers a clear understanding of phase engineering in piezocatalysis and provides an efficiency strategy to construct highly efficient piezocatalysts.