light absorbability, thermal management, water transportation, and water evaporation. [19][20][21][22][23][24][25][26][27][28][29][30][31][32] Among them, the development of sunlight absorbers with rational structure designs has become a popular research topic, because it has remarkable potential to improve η. The absorbers include metallic plasmonics, semiconductors, carbon, and natural materials. [19][20][21][22][23][24][25][26][27][28][29][30][31][32] Among absorber materials, carbon-based materials have low cost, reusability, and excellent light-to-heat conversion properties and accordingly have become a common material in our daily life. [26] However, the operational principle of a carbon-based sunlight absorber in SSG devices is still not understood. Note that the concept for producing steam is very important to design new materials with enhanced efficiency and stability.Here we review some recent progress made in the development of carbon-based sunlight absorbers, including graphene, graphite, carbon nanotubes, other carbon materials, and carbonbased composites, in SSG regarding their fabrication and characterization with special attention paid to material design. The advantages and disadvantages of carbon-based absorbers in SSG are highlighted. Moreover, the challenges of high-performance carbon-based absorbers in solar-driven steam are also discussed. Steam Generation Mechanism for CarbonBased Sunlight Absorbers and Conversion Efficiency Calculation Steam Generation Mechanism for Carbon-Based Sunlight AbsorbersThe mechanism of a plasmonic SSG system has been explored with two plasmonic models. [10,[33][34][35] The first model is surface plasmon polaritons. In this model, the plasmons are able to travel across the surface in the x-y plane of the metal-dielectric interface for tens or hundreds of micrometers and decay to a depth of about 200 nm. [10,33] The second model is localized surface plasmons. It correlates with the Durde-Lorentz model in solid-state physics. According to the conduction band, electrons in the metal can be treated as free electrons, but the positive ions are located in fixed positions. [33] Wang et al. suggested a mechanism for low-temperature solar vapor generation with carbon nanotubes (CNTs) in a suspended system. [29] As shown in

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Activated carbon fibers (ACFs) were surface modified with oxygen plasma at low pressure. The novel effects of the plasma treatment on the microstructural properties of the ACFs were characterized using the Brunauer, Emmett, and Teller method and scanning electron microscopy. Micropores developed on the ACFs. Moreover, the specific surface area and micropore volume increased by 10% at a certain plasma treatment time and power. The changes in the structural properties of the ACFs are discussed in detail with the respect of plasma etching. X-ray photoelectron spectroscopy revealed new oxygen-containing groups, such as CsO, CdO, and OsCdO, had formed on the surface of the ACFs after plasma treatment. Plasma surface oxidative reactions such as the generation of radicals, the combination of the radicals and active oxygen species in the plasma chamber, and the generation of the various oxygen-containing groups are believed to have occurred. The effect of the plasma treatment parameters such as plasma treatment time and power was examined from the perspective of both surface structure and chemistry. It was observed that the micropores and surface functionalities of the ACFs were increased under moderate treatment conditions (50 s and 100 W).