Unveiling the Flexocatalytic Potential of Wide‐Bandgap Spinel Oxides: Light‐Free Hydrogen Evolution via Strain‐Induced Polarization and Oxygen Vacancy Engineering

Abstract Wide‐bandgap spinel oxides, such as ZnAl 2 O 4 (ZAO) and ZnCr 2 O 4 (ZCO), are traditionally limited by poor electron activation under light irradiation, resulting in suboptimal photocatalytic performance. This study investigates a novel approach to overcoming these limitations by leveraging the flexoelectric effect in centrosymmetric porous nanoparticles with wrinkled surfaces. The inhomogeneous strain gradients generated under mechanical force induce flexoelectric polarization, offering a promising pathway to enhance photocatalytic activity. ZAO outperforms ZCO due to the smaller atomic radius of aluminum, allowing greater atomic displacement and higher polarization, which prolongs electron‐hole recombination. Oxygen vacancies (O V ) further enhance ZAO performance, with ZAO‐200 (annealed at 200 °C) achieving the longest carrier lifetime (4.65 ns) and an exceptional hydrogen evolution rate of 3737 µmol g −1 h −1 —206% higher than pristine ZAO—without light stimulation. Density functional theory (DFT) calculations confirm a lower hydrogen evolution reaction (HER) energy barrier for ZAO (ΔG H = −0.13 eV) compared to ZCO (1.34 eV) and reveal spontaneous water splitting at O V sites without energy input. A unique butterfly curve validates flexoelectric potential generation from strain gradients. These findings establish a novel framework for eco‐friendly hydrogen production, demonstrating that flexoelectric polarization and O V engineering can surpass traditional photocatalytic methods in sustainability and efficiency.