This paper demonstrates the use of nanostructured porous hard-carbon florets (NCF) as a solar absorber coating for photothermal water disinfection. NCF coating on helical solar receivers achieves high surface temperatures, heating water to 82 °C and disinfecting it through thermal shock. A prototype, SWAP, delivers bacteria-free hot water at 42 L m⁻² day⁻¹ with a low CO₂ footprint (5 kg L⁻¹), significantly lower than existing methods.
