A clean and membrane-free chlor-alkali process with decoupled Cl(2) and H(2)/NaOH production

Existing chlor-alkali processes generally use asbestos, mercury or fluorine-containing ion-exchange membranes to separate the simultaneous chlorine production on the anode and hydrogen production on the cathode, and form sodium hydroxide in the electrolyte. Here, using the Na(+) de-intercalation/intercalation of a Na(0.44)MnO(2) electrode as a redox mediator, we decouple the chlor-alkali process into two independent steps: a H(2) production step with the NaOH formation in the electrolyte and a Cl(2) production step. The first step involves a cathodic H(2) evolution reaction (H(2)O → H(2)) and an anodic Na(+) de-intercalation reaction (Na(0.44)MnO(2) → Na(0.44−x)MnO(2)), during which NaOH is produced in the electrolyte solution. The second step depends on a cathodic Na(+) intercalation reaction (Na(0.44−x)MnO(2) → Na(0.44)MnO(2)) and an anodic Cl(2) production (Cl → Cl(2)). The cycle of the two steps provides a membrane-free process, which is potentially a promising direction for developing clean chlor-alkali technology.