Fig. 1

Mechanism of two-step chlor-alkali electrolysis. a Schematic illustration of the operation mechanism of the electrolysis cell. Step 1 involves the cathodic reduction of H₂O on the HER electrode and anodic Na⁺ de-intercalation from the Na_0.44MnO₂ electrode in an NaOH solution (Cell 1); Step 2 depends on the cathodic Na⁺ intercalation on the Na_0.44−xMnO₂ electrode and anodic Cl₂ evolution reaction on the CER electrode in a saturated NaCl solution (Cell 2). b Linear sweep voltammetric (LSV) data at a sweep rate of 2 mV s⁻¹ of Na⁺ de-intercalation from Na_0.44MnO₂ in 1 M NaOH (red line) and Na⁺ intercalation in Na_0.44−xMnO₂ in a saturated NaCl solution (blue line); LSV data of the commercial Pt-coated Ti-mesh electrode for HER at a sweep rate of 2 mV s⁻¹ in 1 M NaOH solution (green line); LSV data of commercial RuO₂/IrO₂-coated Ti-mesh electrode for CER in a saturated NaCl solution (black line) at a sweep rate of 2 mV s⁻¹