Boosting hydrogen evolution via flexoelectric catalysis in gradient F-doped hydroxyapatite nanowires

The emergence of flexoelectric effect, which refers to the linear electromechanical coupling between strain gradient and charge polarization in a wide range of materials, suggests a new catalytic mechanism to activate chemical bonds and reactions. Although pioneering studies have shown the remarkable potential for flexoelectric catalysis in a few scenarios, the lack of green, cheap, bio-compatible, and high-efficiency flexoelectric catalysts acts as a major barrier to its expanding applications. In this study, we report the effective design of a high-performance flexoelectric catalyst by simultaneous structural and compositional engineering on hydroxyapatite, a ubiquitous mineral and a well-known biomaterial. By synergizing atomic-scale and nanoscale strain gradients (which are respectively induced by surface lattice doping and geometry engineering) in F-doped hydroxyapatite nanowires (F-HAP NWs), the flexoelectric response together with the catalytic performance of the material are drastically improved, leading to a high hydrogen generation rate (322.7 micromol g^-1 h^-1) in pure water. The findings highlight the potential of F-HAP NWs in flexoelectric catalysis and offer new insights into mechanocatalytic and electrochemical processes in biological systems.