Hierarchical Janus sponge evaporator functionalized with liquid-like PDMS molecular brushes for efficient and sustainable solar evaporation and electricity generation

Abstract

To address the global challenges of freshwater scarcity and the growing demand for clean energy, we report a Janus-structured system based on a polyurethane (PU) sponge scaffold for efficient solar-driven desalination and electricity generation. Through sponge modification, polydimethylsiloxane (PDMS) molecular brushes were integrated with a Janus structure to construct an asymmetric interface featuring a distinct wettability contrast. This design facilitated directional water transport and efficient steam escape pathways, while effectively suppressing contaminant adsorption and pore blockage. Consequently, the device exhibited enhanced solar energy conversion efficiency and effectively achieved simultaneous seawater desalination and electricity generation. Meanwhile, Conductivity measurements confirmed that the ion concentration in the collected freshwater remained consistently low, with Na⁺ levels at 12.9 mg·L⁻¹ and K⁺ levels at 2.2 mg·L⁻¹, both significantly below the World Health Organization (WHO) standards. In addition to desalination, the system also generated an open-circuit voltage of up to 0.5 V, and achieved a maximum evaporation rate of 4.86 kg m⁻² h⁻¹. Long-term stability tests indicated a performance retention exceeding 90 %. These results highlight the significant potential of the fabricated evaporator for sustainable seawater desalination and energy co-generation.