Versatile cationic dual-layer hydrogel filtration system for sustainable solar steam generator

Our increasing water demand has been an ongoing critical challenge due to water usages in areas such as industrial, agriculture, and domestic household. Conventional water production faces challenges, such as high investment, energy consumption, and brine discharge that may be unsustainable in the future. Solar steam generation (SSG) has been recently proposed by many researchers due to their sustainable and green water production method. Here we demonstrated the use of simple manufacturing and low-cost dual-layer hydrogel (DLH) system containing a double network of positive charged poly-[2-(acryloyloxy)ethyl] trimethyl ammonium chloride (PAETAC) and polyvinyl alcohol (PVA) bottom layer for fast water transport, as well as a broad light absorbing and heat generating PVA/graphene oxide (GO) top layer for fast water evaporation. As a result, the DLH was able to generate a high 3.12 kg m−2 h−1 water evaporation with 92% efficiency under 1 sun (kW m−2) exposure. Furthermore, this DLH design allows for a safe and passive anti-salt and bacterial property due to PAETAC cationic chain, eliminating 99% salt and bacteria via Donnan repulsion and electrostatic interaction without the need of sunlight exposure.