Hydrogel-Encapsulated phase change materials for Enhanced heat storage and water evaporation efficiency

• 3.5 kg m -2 h −1 evaporation rate and 12.4 L m −2 day −1 water production yield. • Incorporation of PCMs facilitates high thermal generation and storage. • High temperatures at surface maintained in the absence of sunlight. • Low-cost, anti-salt and bacterial solar steam generator. The solar steam generation (SSG) system is a promising, sustainable, and environmentally friendly technology that has garnered significant attention for its ability to produce freshwater using sunlight as a renewable energy source. However, solar energy is inherently intermittent, as its utilization depends on factors such as time of day and weather conditions, with daytime cloud cover often reducing sunlight intensity and compromising evaporation performance. To address this, we incorporated both hydrophilic and hydrophobic phase-change materials (PCMs) into the top layer of a dual-layer hydrogel (DLH) SSG to enhance heat management. Under solar irradiation, the top evaporating layer generates significant heat, rapidly elevating the surface temperature while the phase change material (PCM) concurrently stores thermal energy. During periods of interrupted solar exposure, the PCM releases stored heat, ensuring continuous water evaporation in the DLH SSG. The system achieved an evaporation rate of 3.52 kg m –2 h –1 under one-sun irradiation, corresponding to an efficiency of 83 %, and sustained an evaporation rate of 26 g m –2 min –1 of lightless operation. Furthermore, the DLH SSG system facilitates salt removal and sterilization via the bottom layer that contained positively charged polymers, thereby offering an effective and practical approach to seawater desalination or lake water treatment to address critical water scarcity challenges.