Strain Gradient Engineering at Material Interfaces: Flexocatalysis Beyond Centrosymmetry

The flexoelectric effect, an electromechanical coupling phenomenon ubiquitous in all materials (including centrosymmetric crystals) under non-uniform strain gradients, has recently given rise to the emerging field of flexocatalysis. By eliminating the need for external light or electrical biases and circumventing the symmetry constraints of piezoelectric materials, it represents a catalytic paradigm for green chemistry, with applications spanning water splitting for hydrogen production, hydrogen peroxide generation, pollutant degradation, and biomedical therapies (e.g., tumor treatment). This review systematically outlines the fundamentals of the flexoelectric effect and the strain gradient-driven charge separation mechanisms. Recent advances in representative applications across energy, environmental, and biomedical fields are comprehensively summarized. Additionally, preliminary strategies to enhance catalytic efficiency are categorized into two main approaches: (1) amplifying the flexoelectric response, primarily interface engineering, the synergistic coupling of piezoelectric and flexoelectric effects, and doping; and (2) optimizing charge separation and transfer, mainly via introduction of vacancies, photo-flexoelectric synergistic coupling, and single-atom modification. Finally, the current challenges and future opportunities of flexocatalysis are highlighted, providing a foundational roadmap that bridges solid-state physics and interfacial catalysis.