• • The CoNiSe2/NiSe2 heterostructure achieves an overpotential of only 108 mV at 100 mA cm−2 in acidic 4.0 M NaCl, outperforming many noble-metal-based catalysts and significantly reducing energy consumption for chlorine production.
• • The hollow porous nanosheet architecture yields an ultra-high specific surface area, enhancing mass transfer and active site exposure, which is critical for achieving industrially relevant current densities.
• • The d-p orbital hybridization between Co/Ni 3d and Se 4p states at the heterointerface lowers the reaction energy barrier for CER, as evidenced by the low overpotential and high Cl2 selectivity, providing a mechanistic basis for catalyst design.
• • The catalyst exhibits excellent stability and Cl2 selectivity in seawater-like electrolytes, addressing the critical challenge of competing OER and ensuring high-purity chlorine output for industrial chlor-alkali applications.