Breaking Symmetry via Bamboo-Inspired Gradient Engineering for Triple-Field Synergistic H₂O₂ Production

Piezocatalysis is a promising chemical synthesis technique, but it is generally restricted to noncentrosymmetric materials, severely limiting catalyst selection. The flexoelectric effect bypasses this symmetry constraint. However, its catalytic contribution is often overlooked, as conventional materials generate only modest strain gradients. Inspired by the hierarchical radial gradients in natural bamboo, we developed radial-gradient BiO(Cl, Br) nanosheets. This architecture breaks the centrosymmetry of BiOCl to invoke robust piezoelectricity while simultaneously amplifying flexoelectricity through built-in mechanical heterogeneity. Driven by a triple-field synergism of built-in, piezo-, and flexoelectric fields, the BiO(Cl, Br) nanosheets achieve a high H₂O₂ production rate of 742.2 µmol g^-1 h^-1, approximately 423% of pristine BiOCl. Theoretical analysis reveals that the mechanical strain and Br doping synergistically modulate the work function and the p-band center, facilitating spin-selective O₂ orbital coupling and reducing the activation barrier for superoxide formation. This work provides an effective strategy to break through symmetry constraints in piezocatalysis, paving the way for the rational design of high-performance mechano-catalysts through gradient engineering.