Flexocatalysis of nanoscale titanium dioxide

Abstract

Piezocatalysis emerges as a distinctive approach for producing free radicals to drive catalysis. However, the piezoelectric effect exclusively manifests in non-centrosymmetric materials, which largely constraints the use of materials with centrosymmetry. To address this challenge, the concept of flexocatalysis is explored to bypass the structural constraints of materials by harnessing strain-gradient-induced polarization, taking advantage of universality of flexoelectricity. As an exemplar of flexocatalysis, centrosymmetric rutile titanium dioxide (TiO2) nano particles are selected due to its high permittivity, non-toxicity, biocompatibility, and wide-ranging utility. The effectiveness of flexocatalysis in generating free radicals (·H, and ·OH) is validated through hydrogen generation (∼2380 μmolg−1h−1 in pure water) and Rhodamine B dye degradation. Additionally, the size effect on flexoelectricity is examined both experimentally and theoretically, revealing that materials at nanoscale exhibit greatly enhanced flexoelectricity that can rival the traditional piezoelectricity. This work endows TiO2 with novel capabilities and broadens material’s selection in mechanochemistry applications.