<p>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.</p>