Atomically dispersed Pt-N₄ sites as efficient and selective electrocatalysts for the chlorine evolution reaction

Chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. Although precious metal-based mixed metal oxides (MMOs) have been widely used as CER catalysts, they suffer from the concomitant generation of oxygen during the CER. Herein, we demonstrate that atomically dispersed Pt-N₄ sites doped on a carbon nanotube (Pt₁/CNT) can catalyse the CER with excellent activity and selectivity. The Pt₁/CNT catalyst shows superior CER activity to a Pt nanoparticle-based catalyst and a commercial Ru/Ir-based MMO catalyst. Notably, Pt₁/CNT exhibits near 100% CER selectivity even in acidic media, with low Cl^- concentrations (0.1 M), as well as in neutral media, whereas the MMO catalyst shows substantially lower CER selectivity. In situ electrochemical X-ray absorption spectroscopy reveals the direct adsorption of Cl^- on Pt-N₄ sites during the CER. Density functional theory calculations suggest the PtN₄C₁₂ site as the most plausible active site structure for the CER.