Process‐Engineered Hierarchical CoO _x Nanowire/Nanosheet Architectures for Selective Chlorine Evolution, Continuous Mineral Extraction, CO ₂ Capture, and Scaling Prevention in Brine Electrolysis

Directly grown CoO_x nanowire/nanosheet architectures on phosphoric acid-treated Ti paper (P-Ti/CoO_x) are developed as highly efficient and durable anode electrodes for selective chlorine evolution from desalination reject brine. The hierarchical CoO_x architecture on the mechanically robust and corrosion-resistant Ti paper substrate enhances electron and ion transport, accelerates surface reactions, and suppresses competing oxygen evolution, resulting in efficient and highly selective chlorine production. This structure enables the P-Ti/CoO_x electrode to achieve ∼93% faradaic efficiency in the chlorine evolution reaction (CER) while maintaining remarkable stability over 70 h of continuous operation. Electrochemical analyses reveal that the first electron transfer step (Cl^- → Cl_ads + e^-) is rate-limiting, with surface-mediated processes dominating CER kinetics. Integration into a flow-cell device demonstrates simultaneous Cl₂ production, mineral extraction, and CO₂ capture from desalination reject brine over 50 h without electrode scaling or membrane fouling. These results strongly demonstrate that P-Ti/CoO_x as a robust, high-performance anode capable of coupling Cl₂ generation with brine valorization and carbon mineralization, offering a practical approach for sustainable electrochemical resource recovery.