Solar steam generation has become a hot research topic because of its great potential to alleviate the drinking water crisis without extra energy input. Although some efforts focusing on designing spatial geometry have been made to multiply the evaporation performances of up-to-date three-dimensional evaporators, they still have some shortcomings, such as low material and space utilization efficiencies, complex spatial geometry, energy loss due to the hot solar absorption surface, and salt crystallization due to inefficient water supply. Herein, a biomimetic copper-based metal−organic framework (Cu−Cu(OH) 2 -MOF) foam sheet with interconnected pores and pine needle-like hierarchical structures consisting of Cu(OH) 2 nanowires and MOF nanowhiskers is fabricated. The pine needle-like hierarchical structures of Cu−Cu(OH) 2 -MOF foam contribute to absorbing solar energy and supplying sufficient water by trapping incident light and enhancing the capillary force, respectively. Inspired by drying clothes outside under solar irradiation, through exposing one end of the Cu−Cu(OH) 2 -MOF foam to air, the biface evaporator achieves a subambient evaporation surface temperature and an evaporation rate of up to 3.27 kg m −2 h −1 under only one sun illumination. Furthermore, when coupled with an air flow, the biface evaporator realizes an excellent evaporation rate of 11.58 kg m −2 h −1 with an energy efficiency of 160.07% even in seawater, ensuring its great application prospect to be used in drinking water production and seawater desalination.

Direct ink writing (DIW) of aerogels has great potential in designing novel three-dimensional (3D) multifunctional materials with hierarchical structures ranging from the nanoscale to the macroscopic scale. In this paper, pure aerogels composed of inorganics, strongly cross-linking organics, and weakly cross-linking organics were directly written via the precise control of the gelation degree without using any additives. The rheological properties of a resorcinol–formaldehyde aerogel-based sol–gel ink (marked as RA ink) were measured at different reaction times to determine the suitable printable range (G′LVR: several 103 Pa) that ensures its good print fidelity. In addition, the rheological evolution of the RA ink during the sol–gel process and under different shear stresses was studied. The correlation of relevant parameters was established according to the Hagen–Poiseuille model. Other typical aerogel-based sol–gel inks including a silica aerogel-based sol–gel ink (SA ink) and a polyimide aerogel-based sol–gel ink (PA ink) for DIW were also demonstrated. Finally, water evaporation experiments were carried out using a 3D-printed carbonized resorcinol–formaldehyde aerogel (CA) to further exhibit the potential applications of this novel technology in solar steam generation. The evaporation rate (1.57 kg m–2 h–1) and efficiency (88.38%) of 3D-printed CA were higher than those of bulk CA (1.21 kg m–2 h–1 and 69.82%). This paper systematically studies the control of DIW parameters for aerogel-based sol–gel inks and shows a potential application in high-efficiency 3D-printed evaporators.

the specific capacitances of supercapacitor electrodes measured by area or volume are the primary consideration for electrochemical energy storage within miniaturized footprint area. [11][12][13] Besides, for supercapacitor electrodes, the design of more doses of active materials means that there exists plenty of active sites available for reversible redox reactions. [14] As a result, it seems desirable to configure a supercapacitor electrode with a high mass loading (per unit area or volume) of active materials, such as a relatively dense distribution or a large thickness. However, such designs usually tend to cause the sluggish electron/ion diffusion, as well as the insufficient use of active materials, which instead limits the overall performance of supercapacitors. [15,16] Carbon aerogel (CA) is a type of hierarchically porous material ranging from micropores to macropores, which exhibits excellent application prospects in catalysis, adsorption, sensing, water evaporation, bone regeneration, electromagnetic shielding, and energy storage. [17][18][19][20][21][22][23][24] Especially, because of the excellent properties such as abundant porosity, ultrahigh specific surface area, good electrical conductivity, excellent infiltration, and good mass transfer ability, CA is considered as a promising electrode material in supercapacitors. [13,[25][26][27] Over the past few years, many efforts have been focused on modifying the pore size distribution of CA to further improve specific capacitance. The abundant micropores and small mesopores for CA are beneficial to the increase of specific capacitance due to a significant increase in specific surface area and active sites. [28] Interestingly, larger mesopores (20-50 nm) are detrimental to the specific capacitance due to the barrier effect for ion diffusion. [29,30] The precise control of sol-gel process was usually used to avoid these larger mesopores. [31] In addition, macropores, as well as micrometer-level or even sub-millimeter-level channels are also conducive to the improvement of specific capacitance, because of the unimpeded channels for electrolyte entry and replacement. [25,28,[32][33][34][35] However, excessive larger channels are unfavorable for their mechanical properties and loading amount of active materials. [16,23] Therefore, the hierarchical pores ranging from nanometer to sub-millimeter scale other than larger mesopores A well-designed pore structure and optimized interface will improve specific capacitances of carbon-based supercapacitor electrodes significantly. Herein, a simple strategy is used to prepare the hierarchically porous 3D-printed carbon aerogel (CA) electrodes via combining direct ink writing, freezing drying, carbonization, and polypyrrole (PPy) posttreatment. The 3D-printed CA electrodes without PPy present a quasi-proportional increase in areal capacitance as thickness, achieving an extremely high areal capacitance of 6875 mF cm -2 under a thickness of 2.2 mm. Additionally, PPy posttreated 3D-printed CA (PPy@CA) electrode has improve...

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The rigorous viscoelastic rheology limits the ink formulation for 3D-printed carbon aerogels (CAs), making their functional customization challenging. Herein, we functionalize 3Dprinted CAs via a unique combination of liquid phase deposition and thermal treatment. The electrodes' improved areal capacitance after functionalization is 3949 mF cm −2 , exceeding that of the pure 3D-printed CA electrode by 33.4%, which is superior by comparison with the carbonaceous electrodes reported previously. These impressive results highlight the effectiveness of this strategy for further functionalization of 3D-printed CAs. Moreover, numerous other potential applications, including catalysis, electromagnetic shielding, and solar steam generation, may be inspired by these findings.