# Characterizations of Interfacial Solar Water Evaporation
## 2 Intrinsic Properties
### Fourier Transform Infrared Spectroscopy  
Fourier transform infrared spectroscopy (FTIR) offers quantitative and qualitative analysis for organic and inorganic samples. FTIR identifies chemical bonds in a molecule by producing an infrared absorption spectrum. The spectra produce a profile of the sample, a distinctive molecular fingerprint that can be used to screen and scan samples for many different components. FTIR is an effective analytical instrument for detecting functional groups and characterizing covalent bonding information.  
[PERSON] et al. [9] described carbonized mushrooms as effective solar steam generators. They used FTIR to confirm the presence of C-N/N-H in the wetting process of original and carbonized mushrooms at 3346 and 1078 cm\({}^{-1}\), 3390 and 1111 cm\({}^{-1}\), respectively (Figure 2a). [PERSON] et al. [10] proposed a cheap and sustainable 3D porous dome array evaporator that achieves broadband spectrum absorption, thermal insulation, and high  
Figure 1: X-ray diffraction patterns. (**a**) The freeze-dried Ti\({}_{3}\)C\({}_{2}\) MXene. Reproduced with permission from ref. [5]. Copyright 2017, American Chemical Society. (**b**) WO\({}_{3}\) and WO\({}_{2.9}\) nanorods. Reproduced with permission from ref. [6]. Copyright 2018, Wiley-VCH. (**c**) MHS. Reproduced with permission from ref. [7], Copyright 2018, Wiley-VCH. (**d**) SnSe@SnO\({}_{2}\) structure. Reproduced with permission from ref. [8], Copyright 2018, The Royal Society of Chemistry.  
hydrophilicity for highly efficient water evaporation and self-desalination. They used FTIR to show that the surface functional groups of carbonized sucrose mainly included C-O, O-H, and C-C, and the content of hydrophilic groups decreased significantly, especially the O-H, indicating that the deoxygenation reaction had happened (Figure 2b). [PERSON] et al. (2017) described a simple method for making flexible anti-biofouling fiber photothermal membranes by coating cellulose membranes with MXene for extremely effective solar evaporation. The FTIR spectrum showed C-F and -OH groups on the surface of MXene as two distinctive peaks at 1375 and 575 cm\({}^{-1}\), respectively. The typical MXene/cellulose membrane absorption bands at 663 cm\({}^{-1}\) (-OH out-of-plane bending), 1639 cm\({}^{-1}\) (-OH bending), and 2920 cm\({}^{-1}\) (C-H stretching) were observed after dip-coating treatment (Figure 2c). [PERSON] et al. (2018) observed an extraordinarily high water vapor production rate in a floating carbonized bamboo sample. The characteristic cellulose structure was visible in the FTIR spectrum. The carboxylate groups in both the original and carbonized bamboos caused peaks at 1124 and 1605 cm\({}^{-1}\), which indicated that they both had a large amount of oxygen-containing functional groups. The original and carbonized bamboo had peaks at 3402 and 3415 cm\({}^{-1}\), respectively, corresponding to N-H, and peaks at 1047 and 1041 cm\({}^{-1}\), respectively, corresponding to C-N (Figure 2d).  
Figure 2: FTIR spectra. (**a**) Carbonized mushrooms. Reproduced with permission from ref. [9], Copyright 2017, Wiley-VCH. (**b**) The porous dome array evaporator. Reproduced with permission from ref. [10], Copyright 2024, The Royal Society of Chemistry. (**c**) The flexible anti-biofouling fiber photothermal membranes. Reproduced with permission from ref. [11], Copyright 2019, American Chemical Society. (**d**) The carbonized bamboo. Reproduced with permission from ref. [12], Copyright 2019, Wiley-VCH.