Defect Engineering Centrosymmetric 2D Material Flexocatalysts

Abstract

In this study, the flexoelectric characteristics of 2D TiO₂ 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 TiO₂ 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 TiO₂ nanosheets. In addition, the TiO₂ nanosheets degraded Rhodamine B, with k_obs being ≈1.5 × 10^-2 min^-1 in dark, while TiO₂ nanoparticles show only an adsorption effect. 2D TiO₂ nanosheets achieve a hydrogen production rate of 137.9 µmol g^-1 h^-1 under a dark environment, 197% higher than those of TiO₂ nanoparticles (70.1 µmol g^-1 h^-1). The flexopotential of the TiO₂ 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 H₂O on the surface of the TiO in the dark. The present findings provide novel insights into the role of TiO₂ flexocatalysis in electrochemical reactions.

Keywords: 2D materials; centrosymmetric; defect Engineering; flexocatalysts.