Efficient piezocatalytic hydrogen peroxide generation over MAX phase piezocatalysts

Piezocatalysis, a new catalysis technology much relying on catalyst's piezoelectric property, attracts unprecedented research enthusiasm for applications in energy conversion and chemical synthesis, such as hydrogen peroxide production. However, the reported piezocatalytic activities are not ideal and one of the reasons is the unsatisfactory piezoelectricity, urging researchers to explore new and efficient piezocatalysts. Herein, the MAX phase materials (Ti3AlC2, Ti3AlCN, and Ti3SiC2) are employed as piezocatalysts for hydrogen peroxide (H2O2) and reactive oxygen species generation. Results suggest that Ti3SiC2 possesses the highest piezocatalytic activity with a notable H2O2 yield of 871.0 μmol/g/h accompanied with small amount of reactive oxygen species, while the Ti3AlC2 and Ti3AlCN deliver relatively lower H2O2 yields of 810.6 and 835.6 μmol/g/h in pure water, respectively. A series of characterizations and analysis have been employed to understand the insights of piezocatalytic activity difference and reaction mechanism. The enhanced peizocatalytic activity of Ti3SiC2 can be traced to its notable piezoelectric property and reduced electronic transfer resistance as well as the improved free charge density, all of which are favorable factors benefiting the piezocatalytic H2O2 generation. Moreover, H2O2 production via piezocatalysis stems from both oxygen reduction and water oxidation.