Chlorine is an indispensable industrial chemical, underpinning the production of pharmaceuticals, disinfectants, and polymers such as polyvinyl chloride. However, more than 95% of global chlorine production currently relies on the conventional chlor-alkali process, which consumes large amounts of electricity, requires highly purified brine, and contributes substantially to carbon emissions.

In a study published in Nature Synthesis, a research team led by Prof. ZHAO Shenlong from the National Center for Nanoscience and Technology (NCNST) of the Chinese Academy of Sciences developed ultrafine high-entropy alloy nanowires (UF-HEANWs) as highly efficient and durable electrocatalysts for the direct electrosynthesis of chlorine from seawater, offering a low-cost and energy-efficient alternative to the century-old chlor-alkali process.

Researchers designed one-dimensional UF-HEANWs composed of Pt, Ni, Co, Fe, and Mo. Owing to their ultrathin morphology and lattice-distorted structure, the nanowires were enriched with abundant atomic steps and unsaturated coordination sites, which are highly favorable for the chlorine evolution reaction.

When integrated into a seawater flow electrolyzer, the UF-HEANW anodes achieved a chlorine selectivity of 98.1% at an industrial-scale current density of 10 kA m^-2, while maintaining continuous operation for over 5,500 hours. Even under harsh acidic seawater conditions at 80 °C, the electrocatalyst exhibited negligible performance degradation and minimal platinum dissolution, demonstrating exceptional long-term durability.

Operando spectroscopic studies revealed that the outstanding performance originated from the dynamic formation of high-valent Pt-O active sites during the operation. The lattice distortion and atomic-step features of the high-entropy nanowires induced localized electronic heterogeneity, which promotes chloride adsorption, facilitates chlorine desorption, and effectively suppresses competing oxygen evolution reaction.

A techno-economic analysis highlighted the advantages of the new electrocatalyst. Direct chlorine electrosynthesis from seawater using HEA anodes reduced the total production cost to US$463.7 per ton of chlorine which is 32.8% lower than that of the conventional chlor-alkali process. The cost reduction was primarily attributed to a 51.3% decrease in electrolysis energy consumption via HEA anodes and an 83.1% reduction in feedstock costs by replacing purified brine with abundant seawater.

This work demonstrates a viable way for sustainable chlorine production by coupling advanced HEA nanomaterials with seawater electrolysis. It not only provides a scalable and economically competitive alternative to traditional chlor-alkali technologies, but also highlights the transformative potential of high-entropy materials in addressing challenges at the energy-water nexus, particularly in harnessing Earth-abundant seawater resources for carbon-neutral chemical synthesis.