Defect Engineering Centrosymmetric 2D Material Flexocatalysts.

In this study, the flexoelectric characteristics of 2D TiO 2 nanosheets are examined. The theoretical calculations and experimental results reveal an excellent strain-induced flexoelectric potential (flexopotential) by an effective defect engineering strategy, which suppresses the recombination of electron-hole pairs, thus substantially improving the catalytic activity of the TiO 2 nanosheets in the degradation of Rhodamine B dye and the hydrogen evolution reaction in a dark environment. The results indicate that strain-induced bandgap reduction enhances the catalytic activity of the TiO 2 nanosheets. In addition, the TiO 2 nanosheets degraded Rhodamine B, with k obs being ≈1.5 × 10 -2  min -1 in dark, while TiO 2 nanoparticles show only an adsorption effect. 2D TiO 2 nanosheets achieve a hydrogen production rate of 137.9 µmol g -1  h -1 under a dark environment, 197% higher than those of TiO 2 nanoparticles (70.1 µmol g -1  h -1 ). The flexopotential of the TiO 2 nanosheets is enhanced by increasing the bending moment, with excellent flexopotential along the y-axis. Density functional theory is used to identify the stress-induced bandgap reduction and oxygen vacancy formation, which results in the self-dissociation of H 2 O on the surface of the TiO in the dark. The present findings provide novel insights into the role of TiO 2 flexocatalysis in electrochemical reactions.