Strain-induced faceting of Ti₄O₇ for active chlorine electrosynthesis

Electrosynthesis of bulk chemicals such as active chlorine depends on the most reactive crystal facets, yet these facets are often thermodynamically disfavored during crystal growth. Here, we present a faceting strategy that integrates 3D printing with electric field inducement to reorient triclinic Ti₄O₇, realizing a dominant facet transition from (1 - 2 0) to high-energy (0 2 - 2) by storing and releasing strain energy to promote the preferential growth of crystal. Such transition trigger active site switching from O on pristine (1 - 2 0) facet to Ti on the reoriented (0 2 - 2) facet, greatly boosting the active chlorine generation rate to a comparable level (0.19 mg·min^-1·cm^-2) to benchmark dimensionally-stable anodes while suppressing parasitic water activation. A flow-by reactor reaches high active chlorine generation rates of 0.33-0.35 mg·min^-1·cm^-2 within 2.9-8.9 s, outperforming industrial dimensionally-stable anodes. This strain-induced faceting approach establishes a general paradigm for controllable crystal reorientation and underscores the potential of 3D printing to expand facet engineering for advanced catalytic systems.