A solar-driven photo-thermoelectrochemical osmotic system with functions of water purification, metal recovery and power generation
A solar-driven and autonomous photo-thermoelectrochemical osmotic system (PTECOS) is developed to simultaneously regenerate freshwater and recover high-value metal from wastewater, providing a sustainable approach to global resource scarcity. This system employs a novel g-C 3 N 4 /TiO 2 @CF photoanode that enables water purification and metal recovery without the need for external energy input. The integration of a forward osmosis (FO) membrane ensures continuous water replenishment via evaporation-induced osmotic gradients while effectively suppressing salt accumulation on the photoanode surface. By combining efficient photothermal evaporation with enhanced photoelectrochemical conversion in a unified design, PTECOS significantly outperforms conventional photoelectrochemical osmotic systems. The optimized system achieves an interfacial evaporation rate of 1.32 kg m −2 h −1 under 100 mW cm −2 illumination, coupled with an FO water flux of 1.30 L m −2 h −1 . It enables copper recovery at 7.8 mg cm −2 h −1 and reaches a peak power density of 1448.6 mW m −2 . The purified water satisfies the World Health Organization (WHO) and the United States Environmental Protection Agency (EPA) drinking-water standards for the examined contaminants. Field tests under natural sunlight demonstrate stable day-night operation. By integrating photothermal evaporation, photoelectrochemical processes, and osmotically-driven water transport, PTECOS overcomes the traditional trade-off between evaporation efficiency and salt accumulation, achieving energy-autonomous freshwater regeneration and efficient metal recovery. This versatile platform offers a promising path toward sustainable water-treatment technologies that combine energy self-sufficiency with resource recovery, thereby addressing the pressing challenges of global resource scarcity.
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