The microscopic structures of the absorbers were characterized by a scanning electron microscope (FEI Strata, Dual-beam FIB 235). The absorption spectra of the absorbers were measured by ultraviolet-visible spectroscopy (UV-3600, Shimadzu) attached with an integrating sphere (ISR-3100). A surface tension/contact angle meter (GBX Digidrop) was used to test the water contact angle of the sample. The thermal diffusivity (α) and specific heat (c) of the absorber were measured by using a NETZSCH LFA457 instrument in argon atmosphere. A Reineisen sample (Ø12.7 mm by 1.98 mm) was used as a standard at room temperature. Thermal conductivity was then calculated by λ = αρc, in which ρ is the density of the absorber. To evaluate the water purification effect of the WHS device, we collected the vapor via the setup in fig. S9. The concentrations of cations in condensed vapor were examined by ICP-OES (PerkinElmer Instruments, PTIMA 5300 DV). The IR images of the absorber surface were captured by an IR camera (FLUKE, Tix 580). The IR emittance spectra of the solar absorbers were measured by a Fourier transform IR spectrometer (Nicolet iS50, Thermo Fisher Scientific).