Understanding the piezocatalytic properties of the BaTiO 3 (001) surface via density functional theory.

Piezoelectric materials have been reported to possess catalytic activity under mechanical excitation, such as by ultrasonic waves or collisions. Energy band theory (EBT) is often used to explain the piezocatalytic phenomenon caused by the strain-induced charge separation, but the correlation between the piezoelectric polarization and catalytic activity has still not been fully understood in early theoretical studies with the EBT model. To reveal the intrinsic connection between the piezoelectric feature and surface catalytic activity, in this work, we employ first-principles Density Functional Theory (DFT) to investigate the prototype piezocatalyst BaTiO 3 (001) surface (BTO). Our simulation shows that the thickness of BTO has a significant impact on the band structure, polarization charge distribution and the surface work function of both positively and negatively polarized sides. As the driving force of piezocatalysis, the electrostatic potential difference (piezopotential) of the two sides shows strong a correlation with the band structure change under the applied strain, which determines the theoretical catalytic activity of BaTiO 3 (001) for water splitting. Finally, we reveal the piezoelectric effects on the surface adsorption energy of H and OH species, which provide a new insight into the mechanism of piezocatalysis. Our work provides a new and in-depth physical insight into the fundamental mechanism of piezocatalysis, which may have important implications for the application of piezocatalysts in water treatment and renewable energy technologies.