Atomically Dispersed Pt–N4 Sites as Efficient and Selective Electrocatalysts for the Chlorine Evolution Reaction

Abstract

Chlorine evolution reaction (CER) is a critical anode reaction in various processes, such as the Cl2 production by chlor-alkali electrolysis and the direct disinfection of ship ballast water or wastewater. Although precious metal-based mixed metal oxides (MMOs) have been prevalently used as CER catalysts, they inevitably suffer from the concomitant absorption of water, the initial step of oxygen evolution reaction (OER). The two anodic reactions share the same active sites of MMOs, and this competetion therefore degrade an overall efficiency of electrocatalytic process. Herein, we demonstrate that atomically dispersed Pt＆minus;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＆minus; concentrations (0.1 M), as well as in neutral media, wherein the MMO catalyst shows substantially lower CER selectivity. In situ electrochemical X-ray absorption spectroscopy reveals the direct adsorption of Cl＆minus; on Pt＆minus;N4 sites during the CER. Density functional theory calculations identify the PtN4C12 site as the most plausible active site structure for the CER.