Few-layer transition metal dichalcogenides (MoS2, WS2, and WSe2) for water splitting and degradation of organic pollutants: Understanding the piezocatalytic effect

Piezoelectric materials have promising potential for converting mechanical energy into chemical energy (i.e. piezocatalysis) by coupling the piezotronic effect with electrochemical processes. Herein, piezocatalytic water splitting and degradation of organic pollutants have been realized in three few-layer transition metal dichalcogenides (TMDs) (namely MoS2, WS2, and WSe2). We showed that the H2 evolution rate reached 29.1, 15.4, and 11.3 μmol g−1 h−1 for MoS2, WS2, and WSe2 nanosheets respectively, under mechanical force provided by ultrasonic vibration. Moreover, their piezocatalytic activities can be further promoted by loading with heavy metal (e.g. Pt and Au) nanoparticles. In addition, all the samples exhibited good piezocatalytic degradation efficiency and reusability toward different organic pollutants (e.g. tetracycline and Rhodamine B). We also provided a systematic investigation on the piezoelectricity by piezoresponse force microscopy and piezoelectric stress coefficients (e11) by first-principle calculations of these three studied compounds, which are accordant with the piezocatalytic results. The present work clearly demonstrates a high correlation between piezoelectricity and mechanical vibration induced catalytic reactions in few-layer TMDs and may provide insight into the mechanisms of piezocatalytic effect.