Gradient Polyelectrolyte Hydrogels Regulated by the Hofmeister Effect for Enhanced Salinity Energy Conversion

The use of asymmetric ion-selective membranes for harvesting salinity energy has attracted widespread attention.Among them, gradient polyelectrolyte hydrogels exhibit excellent power generation potential due to their abundant charged groups and ion rectification behavior.However, swelling induced by high osmotic pressure often disrupts the gradient structure, thereby compromising energy conversion performance.To address this issue, gradient polyelectrolyte hydrogels regulated via Hofmeister effect are designed for efficient osmotic energy conversion.The gradient hydrogels present higher build-in potential, enhanced ionic rectification and improved mechanical properties following Hofmeister series.Among them, potassium sulfate with strong hydration affinity effectively promotes polymer chain aggregation through hydrogen bonding and hydrophobic interactions, thereby significantly improving transport properties of cations.The optimized hydrogel achieves a maximum output power density of 24.3 W/m² under a 1000-fold salinity gradient and maintains stable power output during long-term operation in natural seawater.This work utilizes the Hofmeister effect to regulate the gradient structure of hydrogels, enhancing ion transport properties, and provides a highly promising strategy for developing high-performance polyelectrolyte hydrogel membranes for efficient and stable salinity energy conversion.