Biomass / mxene composite aerogel and preparation method and application thereof

Abstract

This invention relates to the field of solar desalination technology, specifically to a biomass / MXene composite aerogel, its preparation method, and its applications. By introducing sodium lignosulfonate, this invention significantly enhances the oxidative stability of MXene under exposure to air, light, humidity, and heat. First, sodium lignosulfonate adsorbs onto the MXene surface to form a protective layer, preventing MXene from contacting reactive oxygen species. Second, it contains abundant aromatic rings, sulfonic acid groups, phenolic hydroxyl groups, and aliphatic hydroxyl groups. These functional groups interact with oxygen-containing, fluorine-containing, and defective Ti sites on the MXene surface through hydrogen bonding, electrostatic interactions, and π-Ti interactions, passivating defect sites on the MXene surface and edges. Furthermore, the strong antioxidant activity of the phenolic hydroxyl groups and ortho-methoxy groups in sodium lignosulfonate preferentially scavenges oxygen species and free radicals, thereby preventing their attack on the Ti-C bonds in MXene.

Description

Technical Field

[0001] This invention relates to the field of solar seawater desalination technology, specifically to a biomass / MXene composite aerogel, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Freshwater scarcity and soaring energy demand have become global challenges. However, solar-driven interfacial evaporation technology has emerged as an effective way to address the freshwater and energy crises due to its sustainability, eco-friendliness, and cost-effectiveness.

[0004] The evaporation materials determine the performance of solar interface evaporators used for seawater desalination and evaporation-driven power generation. These materials typically consist of a light absorber and a supporting matrix. The light absorber converts solar radiation into heat, while the supporting matrix facilitates water transport and reduces heat loss to the water body and the surrounding environment. The light absorber is crucial for improving solar energy utilization. Since the wavelength range of sunlight reaching the Earth's surface is 300 nm to 2500 nm, it is necessary to select a light absorber with broad spectral coverage. Currently, candidate materials such as metal nanomaterials, inorganic semiconductors, carbon-based materials, and polymers have been reported; however, metal nanomaterials are often hampered by narrow absorption bands and high costs; traditional inorganic semiconductors typically exhibit limited spectral absorption, requiring combination to broaden the range; while carbon-based materials offer broad absorption, their synthesis often involves energy-intensive, high-temperature processes; polymers such as polydopamine and poorly hydrophilic polypyrrole suffer from weak bonding with the matrix. In contrast, Ti3C2T... x MXene exhibits a strong surface plasmon resonance effect, achieving a photothermal conversion efficiency of nearly 100%. In addition, its two-dimensional layered structure and high specific surface area significantly enhance its near-infrared light absorption capacity. These properties make MXene highly suitable as a light absorber.

[0005] Despite its excellent hydrophilicity, MXene is easily oxidized in humid, airy, heated, and light-exposed environments, compromising its chemical stability. Oxidation typically begins with structural defects. In humid, airy, heated, and light-exposed environments, water, oxygen, or generated free radicals nucleophilically attack the Ti-C bonds in MXene, forming TiO2 nuclei and amorphous carbon. Subsequently, the growth and diffusion of TiO2 leads to the degradation of the MXene structure, ultimately transforming MXene completely into TiO2 and amorphous carbon, which significantly weakens its properties. Summary of the Invention

[0006] To overcome the above problems, the present invention provides a biomass / MXene composite aerogel, its preparation method and application.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a biomass / MXene composite aerogel comprising MXene, sodium lignosulfonate (SL), and TEMPO oxidized cellulose nanoparticles (TOCNF).

[0009] The biomass / MXene composite aerogel has a porous structure with vertically arranged channels, and one side of the surface perpendicular to the arranged channels is modified with polydimethylsiloxane (PDMS).

[0010] In one or more embodiments, the mass ratio of MXene to sodium lignosulfonate (SL) is (0.5~10):1.

[0011] In one or more embodiments, the mass ratio of MXene to TEMPO oxidized cellulose nanoparticles (TOCNF) is (0.8~1.2):1, preferably 1:1.

[0012] A second aspect of the present invention provides a method for preparing the biomass / MXene composite aerogel described in the first aspect, comprising the following steps:

[0013] (1) Sodium lignosulfonate (SL) and TEMPO oxidized cellulose nanofiber (TOCNF) were added sequentially to the aqueous solution of MXene nanosheets, mixed evenly, and then a crosslinking agent was added. After mixing evenly again, a precursor solution was obtained.

[0014] (2) The precursor solution was transferred to a container with a bottom heat-conducting and a perimeter heat-insulating structure and placed on the surface of the cryo-liquid for directional freezing. Then, it was freeze-dried to obtain the biomass / MXene composite aerogel precursor. The biomass / MXene composite aerogel precursor has a porous structure with vertically arranged channels.

[0015] (3) The single-sided surface of the biomass / MXene composite aerogel precursor, which is perpendicular to the internal channels, is immersed in a polydimethylsiloxane (PDMS) solution and dried to obtain the biomass / MXene composite aerogel.

[0016] In one or more embodiments, in step (1), the thickness of the MXene nanosheet is 2~5 nm.

[0017] In one or more embodiments, in step (1), the concentration of the MXene nanosheet aqueous solution is 5~6 g / L.

[0018] In one or more embodiments, in step (1), the mass ratio of MXene nanosheets to sodium lignosulfonate (SL) is (0.5~10):1.

[0019] In one or more embodiments, in step (1), the mass ratio of MXene to TEMPO oxidized nanocellulose (TOCNF) is (0.8~1.2):1, preferably 1:1.

[0020] In one or more embodiments, in step (1), the crosslinking agent is silane coupling agent KH-560, and the mass ratio of MXene to silane coupling agent KH-560 is (0.5~1.5):1, preferably 1:1.

[0021] In one or more embodiments, in step (2), the cryosol is liquid nitrogen, and the directional freezing time is 10-20 min.

[0022] In one or more embodiments, in step (3), the polydimethylsiloxane (PDMS) solution is a polydimethylsiloxane n-hexane solution, and the mass fraction of polydimethylsiloxane is 1%~3%.

[0023] In one or more embodiments, in step (3), the soaking time is 1 to 2 seconds.

[0024] A third aspect of the present invention provides the application of the biomass / MXene composite aerogel described in the first aspect or the biomass / MXene composite aerogel prepared by the preparation method described in the second aspect as a solar interface evaporator.

[0025] A fourth aspect of the present invention provides a solar interface evaporator comprising the biomass / MXene composite aerogel described in the first aspect or the biomass / MXene composite aerogel prepared by the preparation method described in the second aspect.

[0026] A fifth aspect of the invention provides the application of the solar interface evaporator described in the fourth aspect in evaporation-induced power generation and solar thermal seawater desalination.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) In this invention, the introduction of sodium lignosulfonate (SL) can significantly enhance the oxidative stability of MXene under exposure to air, light, humidity and heat. First, sodium lignosulfonate (SL) adsorbs onto the surface, edges and defects of MXene to form a dense protective layer, preventing it from contacting H2O, O2 or free radicals. Second, sodium lignosulfonate (SL) contains abundant aromatic rings, sulfonic acid groups, phenolic hydroxyl groups and aliphatic hydroxyl groups. These functional groups are physically adsorbed onto the surface and edges of MXene through hydrogen bonds, electrostatic interactions and π-Ti interactions, passivating defect sites on the surface and edges. Furthermore, the strong antioxidant activity of phenolic hydroxyl groups and ortho-methoxy groups in sodium lignosulfonate (SL) can preferentially scavenge oxygen species and free radicals, thereby preventing them from attacking the Ti-C bonds in MXene.

[0029] (2) Solar interface evaporators need to have the ability to transport water quickly. In this invention, MXene, sodium lignosulfonate (SL) and TEMPO oxidized nanocellulose (TOCNF) interact through physical entanglement and chemical cross-linking mediated by silane coupling agent KH-560 to form a robust three-dimensional network structure. During the directional freezing process, the temperature gradient established along the vertical direction of the mold promotes the nucleation and upward growth of the arranged ice crystals, resulting in a composite aerogel with vertical orientation channels, which facilitates effective water transport during the evaporation process.

[0030] (3) Solar interface evaporators require high evaporation rates. In this invention, the hydrophilic functional groups present in MXene, sodium lignosulfonate (SL), and TEMPO oxidized nanocellulose (TOCNF) help reduce the enthalpy of water evaporation, further accelerating the evaporation rate. In addition, the biomass / MXene composite aerogel precursor is modified with polydimethylsiloxane (PDMS) to construct an asymmetric wettability structure (Janus structure), which helps to inhibit salt accumulation and maintain the self-cleaning properties of the surface, thereby maintaining high evaporation efficiency.

[0031] (4) Wide range of light absorption utilization is conducive to efficient evaporation. In this invention, the synergistic effect of MXene and sodium lignosulfonate (SL) and the salt-resistant porous structure of the biomass / MXene composite aerogel surface enhance light absorption, ensuring a continuous energy supply to the evaporation process.

[0032] (5) The mechanical stability ensures the mechanical stability of the biomass / MXene composite aerogel as a solar interface evaporator for evaporation-induced power generation and solar thermal seawater desalination. In this invention, the biomass / MXene composite aerogel exhibits significant mechanical stability, maintaining 99% of its initial stress after 1000 compression cycles at 50% strain.

[0033] (6) Biomass / MXene composite aerogel achieved 937 kJ·kg -1 Its low enthalpy of vaporization, under 1 solar radiation intensity, is 3.68 kg·m⁻². -2 ·h -1 It exhibits a high evaporation rate and an evaporation efficiency of 95.78%. Furthermore, during the evaporation process, the biomass / MXene composite aerogel generates an evaporation flow induced potential, reaching a maximum open-circuit voltage of 170 mV under irradiation with one solar intensity. Attached Figure Description

[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0035] Figure 1 A schematic diagram illustrating the preparation process and application of biomass / MXene composite aerogel;

[0036] Figure 2 Characterization of MXene and MSTA aerogels: a) X-ray diffraction (XRD) patterns of MAX, MXene, SL, TOCNF samples and MSTA aerogel; b) Transmission electron microscopy (TEM) image of MXene; c) Atomic force microscopy (AFM) image of MXene; d) Schematic diagram of MSTA aerogel structure; e and f) Scanning electron microscopy (SEM) images of MSTA aerogel in cross-sectional direction; g and h) SEM images of MSTA aerogel in longitudinal direction; i) Images of MSTA aerogel before and after hydrophobic treatment; j) Fourier transform infrared (FTIR) spectra of TOCNF, SL, MXene, MS, MSK samples and MSTA aerogel; k) X-ray photoelectron (XPS) spectra of MXene, MS samples and MSTA aerogel.

[0037] Figure 3 The Tyndall effect was observed in MXene suspensions;

[0038] Figure 4 The elemental distribution of MSTA aerogel;

[0039] Figure 5The oxidation stability of MXene and MS under ambient air, light, humidity, and heat exposure conditions is shown in Figure 1. Specifically, a) is a schematic diagram of the oxidation behavior of MXene exposed to air, light, humidity, and heat; b) is the high-resolution XPS spectrum of C1s for MXene films before and after exposure; c) is the high-resolution XPS spectrum of C1s for MS films before and after exposure; d) is the high-resolution XPS spectrum of Ti 2p for MXene films before and after exposure; e) is the high-resolution XPS spectrum of Ti 2p for MS films before and after exposure; f) is the XRD pattern of MXene and MS films before and after exposure; and g) is a schematic diagram of the mechanism by which SL protects MXene from oxidative degradation.

[0040] Figure 6 For the stability experiments of MXene and MS solutions, a represents the solution dispersion stability (12 h) and b represents the solution oxidation stability (7 d).

[0041] Figure 7 The figures show the physical properties of MSTA aerogel, where a is a photograph of the MSTA aerogel; b is the density and porosity of the MSTA aerogel at different SL content levels; c is the saturated water content of the MSTA aerogel at different SL content levels; d is the wettability behavior of the lotus leaf-inspired Janus aerogel, and the water contact angles of the hydrophobic and hydrophilic surfaces; e is the salt expulsion performance of the MSTA aerogel; f is the compressive stress-strain curve of the MT aerogel; g is the compressive stress-strain curve of the MSTA aerogel, with insets showing photographs of the MSTA aerogel in its initial state, after 50% compression, and after unloading the external load; h is the stress-strain curve of the MSTA aerogel after 1000 compression cycles at 50% strain.

[0042] Figure 8 The water absorption properties of MSTA aerogel are shown in Figure 1, where a is the MSTA aerogel precursor (unhydrophobic treatment) and b is the MSTA aerogel (hydrophobic treatment).

[0043] Figure 9 For the thermal insulation properties of MSTA aerogel;

[0044] Figure 10 The self-cleaning properties of MSTA aerogel;

[0045] Figure 11 To ensure the structural integrity of the MSTA aerogel after bending 180°;

[0046] Figure 12The interfacial evaporation performance of MSTA aerogel in pure water is shown in the following figures: a) UV-Vis-NIR absorption spectra of MXene, SL, TOCNF, ST, MT, and MSTA aerogels; b) surface temperature of MSTA aerogel under 1 solar intensity irradiation in both wet and dry conditions; c) schematic diagram of the evaporation test apparatus; d) evaporation rate of pure water for each aerogel under 1 solar intensity irradiation; e) evaporation rate of MSTA aerogel under 0.5–3 solar intensities; f) evaporation measurement of MSTA aerogel in pure water after 10 cycles; g) latent heat of heat of pure water and water within the aerogel; h) DSC curves of pure water and water within the aerogel.

[0047] Figure 13 The surface temperature change curves of TOCNF aerogel, ST aerogel, MT aerogel and MSTA aerogel dried under one solar radiation intensity;

[0048] Figure 14 The surface temperatures of moistened TOCNF aerogel, ST aerogel, MT aerogel, and MSTA aerogel after 500 s under one solar radiation intensity.

[0049] Figure 15 Evaporation rates of MSTA aerogels with different SL contents under irradiation at one solar intensity;

[0050] Figure 16 The interfacial evaporation properties of MSTA aerogel are shown in Figure 1; where a is the Raman scattering spectrum of pure water; b is the Raman scattering spectrum of water in MSTA aerogel; and c is the ratio of free water to intermediate water content calculated based on Raman spectroscopy.

[0051] Figure 17 The table shows the brine interface evaporation performance of MSTA aerogel. Specifically, a) is the evaporation rate of the aerogel in a 3.5 wt% NaCl solution under 1 solar radiation intensity; b) is the UV-Vis absorption spectra of MSTA aerogel before and after evaporating methyl orange and methylene blue from simulated industrial wastewater; the inset in b) shows images of the methyl orange solution (left) and methylene blue solution (right) before and after purification; c) is a diagram of a seawater desalination device under natural sunlight; d) is the evaporation rate of MSTA aerogel under solar radiation intensity on a sunny day from 8:00 to 18:00 in Jinan, China, on June 6, 2025; e) is the concentration of major metal ions in the initial seawater (before desalination) and the water collected after desalination; f) is the evaporation rate of MSTA aerogel and MT aerogel in a continuous 30-day evaporation experiment; g) is a photograph of MSTA aerogel and MT aerogel after 7 and 30 days of continuous evaporation.

[0052] Figure 18This diagram shows the evaporation-steam power generation data collection for MSTA aerogels. Specifically, a) is a schematic diagram of the MSTA aerogel power generation mechanism; b) is a schematic diagram of the evaporation power generation test setup; c) shows the Zeta potential of MXene, TOCNF, and MSTA aerogels; d) shows the potential output of MSTA and TOCNF aerogels under 1 solar radiation intensity; e) shows the potential output of MSTA aerogels under both light and dark conditions; f) shows the potential output of MSTA aerogels under different irradiation intensities; g) shows the potential output of MSTA aerogels under sealed and unsealed conditions; h) shows the current and voltage of MSTA aerogels under an applied load; i) shows the power of MSTA aerogels under an applied load; j) shows the potential output of three MSTA aerogels connected in series and parallel; k) shows a photograph of 12 MSTA aerogels illuminating a small screen; and l) shows the long-term evaporation-induced steam power generation performance of MSTA aerogels. Detailed Implementation

[0053] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0054] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0055] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0056] Example 1

[0057] Preparation of MXene:

[0058] 0.9885 g LiF was added to 10 mL of 9 mol / L hydrochloric acid and stirred for 5 min. Then, 1.01 g Ti3AlC2 was slowly added, and the mixture was reacted in a 45 ℃ water bath for 48 h. After the reaction was complete, the precipitate was collected by centrifugation (5300 rpm, 5 min). The precipitate was washed repeatedly with deionized water by centrifugation until the pH of the supernatant was 7. After the last centrifugation, the product was dispersed in deionized water and sonicated (50 kHz) in an ice-water bath for 1 h to exfoliate MXene nanosheets. Finally, the supernatant was collected by centrifugation (6500 rpm, 1 h).

[0059] Example 2

[0060] Figure 1 This diagram illustrates the preparation process and application of biomass / MXene composite aerogels. (Reference) Figure 1 Synthetic biomass / MXene composite aerogel (hereinafter referred to as MSTA aerogel).

[0061] (1) Place 10 mL of 5.4 g / L MXene nanosheet aqueous solution in an ice bath and sonicate (50 kHz) for 30 min; add sodium lignosulfonate (SL), with a mass ratio of MXene to sodium lignosulfonate (SL) of 0.5:1, and stir for 3 h. Add TEMPO oxidized cellulose nanoparticles (TOCNF) of equal mass to MXene to the mixed solution, stir for 1 h, and after mixing evenly, add silane coupling agent KH-560 of equal mass to MXene, and stir again for 6 h to obtain the precursor solution.

[0062] (2) The precursor solution was transferred to a container with a bottom heat-conducting and surrounding heat-insulating structure and placed on the surface of the cryosol. It was directionally frozen for 15 min and then freeze-dried for 48 h to obtain the biomass / MXene composite aerogel precursor. The biomass / MXene composite aerogel precursor has a porous structure with vertically arranged channels.

[0063] (3) Dissolve 0.4 g of polydimethylsiloxane (PDMS) prepolymer (polydimethyl methyl vinyl siloxane) and 0.04 g of crosslinking agent in 19.6 g of n-hexane to obtain a polydimethylsiloxane (PDMS) solution; immerse the single-sided surface of the biomass / MXene composite aerogel precursor perpendicular to its internal channels in the polydimethylsiloxane (PDMS) solution for 1 s, and dry (80 ℃, 3 h) to obtain a biomass / MXene composite aerogel, named MSTA-0.5.

[0064] Example 3

[0065] Compared with Example 2, the mass ratio of MXene to sodium lignosulfonate (SL) was 1:1, and the other methods were the same as in Example 1 to obtain a biomass / MXene composite aerogel, named MSTA-1.

[0066] Example 4

[0067] Compared with Example 2, the mass ratio of MXene to sodium lignosulfonate (SL) was 2:1, and the other methods were the same as in Example 1 to obtain a biomass / MXene composite aerogel, named MSTA-2.

[0068] Example 5

[0069] Compared to Example 2, the mass ratio of MXene to sodium lignosulfonate (SL) was 5:1, and the other methods were the same as in Example 1 to obtain a biomass / MXene composite aerogel, named MSTA-5.

[0070] Example 6

[0071] Compared with Example 2, the mass ratio of MXene to sodium lignosulfonate (SL) was 10:1, and the other methods were the same as in Example 1 to obtain a biomass / MXene composite aerogel, named MSTA-10.

[0072] Comparative Example 1

[0073] Compared to Example 2, MXene and sodium lignosulfonate (SL) were not added, but the other methods were the same as in Example 1 to obtain a composite aerogel, which was named TOCNF aerogel.

[0074] Comparative Example 2

[0075] Compared with Example 2, MXene was not added, but other methods were the same as in Example 1 to obtain a composite aerogel, which was named ST aerogel.

[0076] Comparative Example 3

[0077] Compared to Example 2, sodium lignosulfonate (SL) was not added, but the other methods were the same as in Example 1 to obtain a composite aerogel, which was named MT aerogel.

[0078] Unless otherwise specified, the MSTA aerogel in the following examples is MSTA-5 prepared in Example 5.

[0079] Figure 2 For the characterization of MXene and MSTA aerogels, compared with the MAX phase precursor, the XRD spectrum of the synthesized MXene showed that the (002) peak characteristically shifted from 9.47° to 6.96°, while the peak at 38.96° corresponding to the (104) plane of the MAX phase disappeared. Figure 2 (a) confirms the successful selective etching of the Al layer, while the shift of the (002) peak to a lower angle indicates an increase in interlayer spacing, consistent with Bragg's law; these results collectively validate the successful preparation of MXene. The obtained MXene aqueous dispersion exhibits colloidal properties ( Figure 3 Furthermore, TEM and AFM analyses showed that the exfoliated MXene exhibited a typical two-dimensional sheet-like morphology. Figure 2 (b), with a thickness of approximately 3 nm ( Figure 2 (c) confirmed the formation of monolayer nanosheets.

[0080] The cross-section and longitudinal section of the Janus structured MSTA aerogel were observed by SEM. The cross-section showed a hierarchical porous structure. Figure 2 (e and f), while the longitudinal section shows many vertically arranged microchannels ( Figure 2 (g and h); these channels are surrounded by walls formed by cross-links between TOCNF, LS, and MXene nanosheets. Elemental distribution confirms the uniform distribution of C, O, Ti, and S on the aerogel framework (g and h). Figure 4 This indicates a uniform composite structure. The synergistic combination of the hierarchical pore structure in the cross-section and the vertically arranged channels promotes effective light capture through internal reflection and scattering, while enabling rapid water transport through capillary action in the longitudinal direction. Furthermore, the hydrophobic modification of the surface resulted in no observed cracks or volume changes at the Janus interface. Figure 2 i).

[0081] The chemical structure of the MSTA aerogel was further analyzed by XRD, FTIR, and XPS. FTIR spectra were observed in the 3200–3600 cm⁻¹ range. -1 There is a broad absorption peak between them, corresponding to the OH stretching vibrations from MXene, SL, and TOCNF. The significant broadening of this absorption peak in MSTA aerogel indicates enhanced hydrogen bonding interactions between the components. Figure 2 (j). The presence of Ti, S, and Si signals in the XPS full spectrum confirms the successful introduction of MXene, SL, and the silane coupling agent KH-560. Figure 2 In Example 2, MS was a lyophilized sample without TOCNF and KH-560 solution, and MSK was a lyophilized sample without TOCNF solution. The XRD patterns further supported the composite nature, with a broad peak near 20° and a peak near 23° corresponding to the TOCNF (200) plane. Figure 2 (a) verified that SL and TOCNF were successfully integrated into the aerogel matrix.

[0082] Example 7

[0083] Oxidative stability of SL-protected MXene:

[0084] In MXene-based aerogel solar interfacial evaporators, MXene is the primary light-absorbing material. However, under practical application conditions (exposure to ambient air, light, humidity, and heat), MXene is prone to oxidation. Charged oxygen species or free radicals nucleophilically attack the positively charged Ti atoms in the HO(F)-Ti-C bond on the MXene surface, forming TiO2 and amorphous carbon (…). Figure 5(a) This process ultimately leads to the structural collapse of MXene, thereby reducing the evaporation efficiency of MXene-based aerogel solar interface evaporators. SL is used to protect MXene from oxidation by H2O, O2, or free radicals in the application environment.

[0085] SL was added to an MXene solution (MXene to SL mass ratio 5:1), and the mixture was stirred for 3 h, followed by vacuum filtration to form an MS film. A sample without added SL served as a control. Both samples were then dried in a vacuum oven at 60 °C for 24 h. Subsequently, the samples were exposed to a humid (60% relative humidity), ambient air, heat (60 °C), and light (laboratory light) environment for 120 h. XRD and XPS measurements were performed on both samples before and after the humid-heat-light-air oxidation aging treatment.

[0086] High-resolution XPS analysis showed that after 120 h of exposure to air, light, humidity, and heat, the C 1s spectrum of pure MXene exhibited a significantly enhanced C-C bond peak and a significantly weakened C-Ti bond peak at 285 eV. Figure 5 (b) In the Ti 2p XPS spectrum, after treatment, obvious TiO2 peaks appeared at 459 eV and 464.6 eV, respectively, while the Ti-C bond peaks were significantly weakened. Figure 5 (c) These observations confirm the oxidation of MXene.

[0087] In contrast, under the same conditions, the C 1s and Ti 2p XPS spectra of the MS film showed negligible changes before and after treatment. Figure 5 (d and e) indicate that SL effectively protects MXene from oxidation.

[0088] XRD results further support these findings: pure MXene showed characteristic anatase TiO2 peaks after treatment, while the MS sample remained almost unchanged. Figure 5 (f). Solution dispersion stability and oxidative stability experiments also confirmed the stabilizing effect of SL (f). Figure 6 The protective effect of SL is attributed to its adsorption onto the MXene surface, forming a dense protective layer that prevents contact with H2O, O2, or free radicals. Secondly, it adsorbs onto the MXene surface and edges through hydrogen bonding, electrostatic interactions, and π-Ti interactions, passivating defect sites. Furthermore, the phenolic hydroxyl and ortho-methoxy groups in SL preferentially scavenge negatively charged reactive oxygen species, preventing them from oxidizing the defect sites of MXene. Figure 5 (g). Therefore, MXene maintains its structural integrity under air, light, humidity and heating conditions, thus ensuring the long-term evaporation performance and structural durability of MSTA aerogel in solar evaporation systems.

[0089] Example 8

[0090] Physical properties of MSTA aerogel:

[0091] The physical properties of MSTA aerogel, including density, water absorption, thermal insulation, surface wettability, salt expulsion, self-cleaning properties and mechanical strength, were systematically evaluated to assess its suitability as a solar interfacial evaporator.

[0092] like Figure 7 As shown in Figure a, the MSTA aerogel exhibits an ultra-low density, as evidenced by its ability to remain on the flower stamen without causing deformation; this lightweight property stems from its highly porous structure filled with air. With increasing SL content, the aerogel's density increases while its porosity decreases slightly; even at the highest SL loading, the density remains as low as 18.6 mg / cm³. 3 The porosity is close to 99%. Figure 7 (b). This porous structure enables it to absorb water up to 76 times its own weight. Figure 7 (c) and facilitated rapid water transport; for example, when a 2 cm high MSTA aerogel precursor without surface hydrophobic treatment was placed in a petri dish filled with water, the absorbent paper on top of the MSTA aerogel precursor was rapidly wetted within seconds. Figure 8 (a). Furthermore, when the MSTA aerogel was placed on a heating platform at 105.9 °C, the top surface temperature stabilized at 41.2 °C after 120 s, while the bottom reached 105.9 °C. Figure 9 This indicates that the aerogel possesses effective thermal insulation capabilities. These properties lay a favorable foundation for MSTA aerogels as solar interface evaporators, providing favorable conditions for efficient water transport and localized heat concentration.

[0093] Inspired by lotus leaves Figure 7 (d) The MSTA aerogel forms a Janus-wetting structure on its top surface through PDMS modification, and the hydrophobic top surface exhibits a water contact angle of 141.6°. Figure 7 (d) effectively prevents salt accumulation and achieves self-cleaning ( Figure 10 This hydrophobic layer prevents water from penetrating the top surface of the MSTA aerogel. Figure 8 (b) In contrast, the unmodified bottom surface exhibited superhydrophilicity, adsorbing water droplets within 0.2 s with a contact angle of 0°. Figure 7 (d). This asymmetric wettability facilitates continuous water supply from the bottom while maintaining a dry and salt-free evaporation interface. Salt expulsion was further confirmed by the complete dissolution of 1 g of NaCl solid deposited on the surface of a 2 cm × 2 cm MSTA aerogel within 3 h. Figure 7(e), which is attributed to rapid solute diffusion and the hydrophobic top surface preventing the formation of a salt film. Self-cleaning and salt-barrier capabilities together help maintain high light absorption and uninterrupted vapor diffusion.

[0094] Structural toughness is crucial for the structural durability of aerogel-based solar interfacial evaporators. MSTA aerogels maintain structural integrity after being bent at 180°. Figure 11 This demonstrates their high flexibility. Under compression, both MT and MSTA aerogels recovered well, with MSTA aerogel exhibiting significantly enhanced strength and elastic recovery due to the strong interfacial interaction between SL and MXene nanosheets. Figure 7 (f and g). After 1000 compression cycles, the MSTA aerogel exhibited minimal irreversible deformation (<5%) and retained 90% of its initial stress at 50% strain. Figure 7 The presence of h indicates its excellent fatigue resistance. This mechanical stability stems from the synergistic combination of the three-dimensional network of TOCNF, SL, and MXene formed through directional freezing, and the cross-linked covalent network promoted by the silane coupling agent KH-560. The resulting physical entanglement and chemical bonding produce an ultra-robust, elastic aerogel structure. In summary, MSTA aerogel integrates vertically aligned channels, robust mechanical stability, efficient heat concentration, rapid water transport, and antifouling / salt removal properties into a single material, demonstrating great potential for long-lasting and efficient solar interfacial evaporation.

[0095] Example 9

[0096] The absorption spectra of MXene, SL, TOCNF aerogel, ST aerogel, MT aerogel, and MSTA aerogel were measured in the wavelength range of 250–2500 nm. The results are as follows: Figure 12 As shown in Figure a, TOCNF exhibits low absorption (<50%) across the entire spectral range; while SL shows higher absorption than TOCNF; except in the 250–596 nm range, MXene exhibits superior light absorption compared to SL. In the composite aerogels, MT aerogel (TOCNF / MXene) shows significantly higher absorption than ST aerogel (TOCNF / SL), exceeding 84% across the entire wavelength range; MSTA aerogel, incorporating SL and MXene into TOCNF aerogel, exhibits the highest absorption, exceeding 90% in the 250–1657 nm range. These results indicate that MXene is the dominant light-absorbing component in MSTA aerogel, while SL and the porous aerogel structure synergistically enhance its overall light absorption performance.

[0097] The photothermal conversion properties of the aerogel were monitored under simulated solar irradiation. In a dry air environment, the surface temperature of the MSTA aerogel rapidly increased and stabilized at approximately 85.6 °C within 120 s. Figure 12 (b) The temperature was significantly higher than that observed in TOCNF (34 °C), ST (53 °C), and MT (75 °C) aerogels after prolonged irradiation. Figure 13 In an aqueous environment, the surface temperature of the MSTA aerogel also rises sharply, reaching a stable temperature of 56 °C within 120 s. Figure 12 (b), which is significantly higher than other aerogel samples ( Figure 14 This behavior is attributed to the excellent photothermal conversion properties of SL and MXene. The lower temperature rise in water compared to dry conditions is due to the dissipation of some heat energy during water evaporation.

[0098] The evaporation properties of the aerogel were evaluated under irradiation with one solar intensity. Figure 12 (c) The evaporation rates of pure water, TOCNF aerogel, ST aerogel, MT aerogel, and MSTA aerogel were 0.40 kg·m⁻¹. -2 ·h -1 1.06 kg·m -2 ·h -1 1.81 kg·m -2 ·h -1 2.78 kg·m -2 ·h -1 and 3.68 kg·m -2 ·h -1 ( Figure 12 (d). All aerogels exhibited better evaporation rates than pure water, demonstrating their effectiveness in moisture transport and solar energy utilization. The order of water evaporation rates for aerogels was: MSTA > MT > ST > TOCNF ( Figure 12 (d). MSTA aerogel with a SL to MXene mass ratio of 1:5 achieved 3.68 kg·m³. -2 ·h -1 The highest evaporation rate ( Figure 15 It has a density 9.2 times that of pure water and 3.5 times that of TOCNF aerogel. The evaporation rate increases with different solar intensities (0.5, 1, 2, and 3), reaching 8.38 kg·m³ under the 3 solar intensities. -2 ·h -1 ( Figure 12 (e). Furthermore, the MSTA aerogel maintained stable performance during 10 cycles of evaporation testing. Figure 12 (f), demonstrating excellent reusability and structural stability.

[0099] Notably, except for the TOCNF aerogel, the evaporation rates of the prepared aerogels all exceeded the theoretical limit of pure water, which is 1.47 kg·m -2 ·h -1 calculated under 1 sun intensity with an assumed 100% energy conversion efficiency. To clarify this phenomenon, the latent heat of water in each aerogel was further measured. The latent heat values of water in the TOCNF aerogel, ST aerogel, MT aerogel, and MSTA aerogel were 1496 kJ·kg -1 、1179 kJ·kg -1 、1213 kJ·kg -1 and 937 kJ·kg -1 respectively, all significantly lower than that of pure water (2445 kJ·kg -1 )( Figure 12 in g). The order of decreasing latent heat (MSTA < ST < MT < TOCNF) indicates that the energy required for water evaporation within the confined pore structure of the aerogel is significantly reduced. This reduction directly contributes to the excellent evaporation performance, especially for the MSTA aerogel ( Figure 12 in d). Differential scanning calorimetry (DSC) analysis of the four aerogel samples further confirmed this conclusion ( Figure 12 in h), showing that pure water exhibits the highest thermal stability during the phase change process, while the water evaporation in the MSTA aerogel requires the least energy, confirming its enhanced evaporation kinetics.

[0100] Example 10

[0101] To investigate the fundamental reason for the latent heat difference between pure water and water confined in the MSTA aerogel, the states of free water (FW) and intermediate water (IW) in the two systems were analyzed. Raman scattering spectroscopy was used to characterize the states of water in pure water and the MSTA aerogel. Specifically, the peaks in the spectral range of 2800 - 4000 cm -1 were distinguished into two components: the peaks at 3090 cm -1 and 3245 cm -1 correspond to FW, while the peaks at 3425 cm -1 and 3557 cm -1 correspond to IW. The Raman spectra of water in pure water and the MSTA aerogel are shown in Figure 16 as a and b. As shown in Figure 16 c, the IW / FW ratio in the MSTA aerogel (2.26) is significantly higher than that in pure water (1.09). This can be attributed to the abundant polar functional groups (-COOH, -OH, and -SO3H) in the TOCNF, MXene, and SL components of the MSTA aerogel ( Figure 1These groups increase the proportion of water molecules within the polymer network, promoting the escape of water molecules during evaporation. Therefore, the latent heat of water in MSTA aerogels is lower than that of pure water, thus increasing the evaporation rate.

[0102] Example 11

[0103] To evaluate the evaporation performance of MSTA aerogel in a brine environment, its evaporation rate was tested using a 3.5 wt% NaCl solution. Under solar irradiation, the evaporation rate of TOCNF aerogel in brine was 0.92 kg·m⁻¹. -2 ·h -1 The evaporation rate of ST aerogel is 1.61 kg·m. -2 ·h -1 MT aerogel exhibits a strength of 2.50 kg·m -2 ·h -1 The evaporation rate of MSTA aerogel in brine reached 3.51 kg·m³. -2 ·h -1 evaporation rate ( Figure 17 (a) The evaporation rates of the four aerogels in brine are consistent with those in pure water. However, it is noteworthy that the evaporation rates of all aerogels in NaCl solution are slightly lower than those observed in pure water ( Figure 12 d and Figure 17 (a) This can be attributed to the decrease in vapor pressure caused by solute dissolution. Furthermore, the MSTA aerogel with the highest evaporation rate was used to simulate the purification of industrial dye wastewater. Methyl orange and methylene blue were used as model pollutants to simulate industrial dye wastewater. The condensate collected after evaporation was colorless and transparent. Figure 17 (b) The UV-Vis absorption spectra of the two simulated wastewaters before and after treatment show that the strong absorption peaks in the 340–800 nm range completely disappeared after evaporation. Figure 17 (b) shows a dye removal efficiency close to 100%. These results demonstrate the great potential of MSTA aerogels in seawater desalination and industrial dye wastewater treatment applications.

[0104] To investigate the performance of MSTA aerogel in real seawater evaporation and evaluate its solar desalination capability, a custom-designed condensate collection system was employed. In this setup, the MSTA aerogel floats on the seawater surface and continuously evaporates water under solar radiation. The generated vapor condenses upon encountering a cooler plexiglass cap, and the condensate is collected. Figure 17 (c) The evaporation rate of MSTA aerogel varies throughout the day with fluctuations in solar intensity. Figure 17As shown in Figure d, solar radiation intensity gradually increases before 12:00 noon and then decreases. The evaporation rate of the MSTA aerogel also shows a corresponding trend. The maximum solar radiation intensity of 94.7 mW·cm⁻¹ was recorded at 12:00 noon. -2 At this point, the evaporation rate of the composite aerogel reached 3.19 kg·m³. -2 ·h -1 peak value ( Figure 17 (d). Under these conditions, the MSTA aerogel produced 21.21 kg·m³ during an 11-hour test on June 6, 2025 (from 8:00 AM to 6:00 PM). -2 The purified water. Simultaneously, inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze four major ions in the pristine seawater and desalinated water: Na+. + K + Ca 2+ and Mg 2+ concentration ( Figure 17 (e). The results showed that the ion concentration decreased by approximately 3–4 orders of magnitude. The quality of the desalinated water exceeded the drinking water standards set by the World Health Organization (WHO), further demonstrating the effectiveness of MSTA aerogel in producing safe and clean water. These results confirm the excellent real-time desalination performance of MSTA aerogel under natural light and highlight its potential for large-scale freshwater production in practical applications.

[0105] More importantly, MSTA aerogel exhibited excellent long-term operational stability. After 30 consecutive days of evaporation testing, the evaporation rate of MT aerogel decreased by 37%, while the evaporation rate of MSTA aerogel remained stable. Figure 17 (f). After 7 days, the surface color of MT aerogel lightened, with some areas turning blackish-gray and even grayish-white, while the appearance of MSTA aerogel did not change significantly. Figure 17 (g). After 30 days, MT aerogel showed extensive yellowing, while MSTA aerogel remained largely unchanged. This indicates that MXene underwent significant oxidation. However, the addition of SL in this work delayed the oxidation of MSTA aerogel, endowing it with excellent antioxidant properties, enabling it to maintain stable evaporation performance over a long period.

[0106] Example 12

[0107] MSTA aerogel not only exhibits high evaporation rates and excellent desalination performance under 1 solar radiation intensity, but also demonstrates the ability to generate flow potential from the evaporated vapor. According to the electric double layer (EDL) theory, when water flows through the charged microchannels of the MSTA aerogel, a thin layer of positive ions (H3O) is adsorbed onto the negatively charged functional groups on the channel walls. +Ions outside this adsorption range form an adsorption layer (Stern layer). Ions outside this adsorption range form a diffusion layer (Diffuse layer). The water flow drives the movement of these counterions, thereby generating a potential difference ( Figure 18 (a) Two inert electrodes are attached to the upper and lower surfaces of the MSTA aerogel to measure the flow potential during evaporation. Figure 18 (b) Based on this mechanism, the Zeta potential of the interfacial evaporator will affect its ability to generate flow potential throughout the evaporation process. Figure 18 As shown in Figure c, the Zeta potential of MSTA aerogel was measured to be -25.4 mV, which is higher than that of pure MXene (-17.7 mV). This enhancement can be attributed to the presence of more fully ionized polar groups in MSTA aerogel, including carboxylic acid (-COO-) groups from TOCNF and sulfonic acid (-SO3-) groups from SL. These groups significantly enhance power generation during the solar-driven interfacial evaporation process. Experimental results show that under 1 solar intensity irradiation, the flow potential generated by interfacial evaporation of MSTA aerogel reaches approximately 170 mV, while the flow potential generated by TOCNF aerogel is lower, approximately 46 mV. Figure 18 (d). Although TOCNF aerogels also have many microchannel pores, their evaporation rate is relatively low ( Figure 12 The presence of fewer charged groups on the channel walls (d) hinders the formation of a rapid ion flow, limiting the trapping of charged particles and resulting in a smaller potential difference. Under irradiation with one solar intensity, the potential output of the MSTA aerogel increased from 85 mV and reached 170 mV after 1000 s, after which it remained at a stable level. Figure 18 (e). After the light is turned off, the potential output drops rapidly ( Figure 18 (e). When the light is turned back on, the voltage output again follows the same trend ( Figure 18 (e) indicates that the increase in voltage is directly related to the enhanced water evaporation induced by light irradiation. However, the MSTA aerogel responds relatively slowly to solar irradiation, requiring approximately 1000 s to adapt to environmental changes ( Figure 18 (e). This delayed response is attributed to the synergistic chemical effects of TOCNFs and SL, as well as the confined pore channels, which gives MSTA aerogel high water retention. This property makes it less sensitive to external conditions, preventing the rapid voltage fluctuations common in membrane-based evaporative power generation materials. Furthermore, although the voltage increase is not strictly linearly related to light intensity, the output voltage of MSTA aerogel still increases with increasing solar irradiance (e). Figure 18(f). This is mainly due to the enhanced evaporation rate under stronger irradiation, further confirming the positive correlation between evaporation and power generation. The observed increase in nonlinear voltage can be attributed to the thermal diffusion effect (Soret effect), which originates from the temperature gradient between the aerogel surface and the large amount of water, promoting the generation of H3O. + The migration from the hot side to the cold side reduces the amount of H3O induced by evaporation. + Charge collection occurs in the opposite direction of migration. Furthermore, the voltage output of the MSTA aerogel was measured under both hermetically sealed and unhermetically sealed conditions. Under unhermetically sealed conditions, the open-circuit voltage remained stable at approximately 170 mV under 1 solar radiation intensity. Figure 18 (g). When the device is sealed, the voltage does not drop immediately because the water stored inside the aerogel continues to evaporate ( Figure 18 (g). Once the sealing system reaches water vapor saturation, evaporation stops, and the voltage disappears. Figure 18 (g), which confirms that capillary-driven water flow is the main mechanism for voltage generation in MSTA aerogels.

[0108] The voltage and current variations of MSTA aerogel under different external load resistances (RL) are as follows: Figure 18 As shown in Figure h, as the load resistance increases, the current in the external circuit decreases from 2.5 μA to nearly 0 μA, while the voltage increases from 0 mV to 170 mV. The output power can be expressed using the formula P = I. 2 The calculation is performed using × RL, where I represents the current. For example... Figure 18 As shown in Figure i, the peak output power of the MSTA aerogel reaches 13.52 nW at a load resistance of 800 kΩ. The generated output voltage and current can be amplified to enhance its strength by connecting multiple units in series and parallel, respectively. Figure 18 As shown in Figure j, when three MSTA aerogel units are connected in series, the output voltage reaches 525 mV, while when the same units are connected in parallel, the output current increases to 0.75 mA. Furthermore, a configuration of 12 MSTA aerogel units connected in series can power a 2V LED display. Figure 18 (k). Long-term voltage monitoring of the MSTA aerogel further verified the stability of this flow potential (k). Figure 18 (l).

[0109] Inspired by the biomimetic lotus leaf structure, this invention provides a high-performance MSTA aerogel solar-driven interfacial evaporator with a Janus structure. The top layer mimics the surface of a lotus leaf, exhibiting antifouling properties to prevent salt accumulation while effectively absorbing sunlight; the bottom layer has vertical microchannels for continuous water pumping. The MSTA aerogel exhibits robust mechanical properties and excellent fatigue resistance under long-term compression (over 1000 compression cycles). The porous, vertical channel structure of the MSTA aerogel, combined with MXene and SL photothermal materials, achieves highly efficient broadband absorption. The synergistic effect of TOCNF and SL, along with the low thermal conductivity and heat concentration obtained from the porous structure, enables the developed MSTA aerogel to achieve 937 kJ·kg⁻¹. -1 With its low enthalpy of vaporization, MSTA aerogel reaches 3.68 kg·m³ under irradiation with 1 unit of solar radiation. -2 ·h -1 The composite aerogel exhibits a high evaporation rate and an evaporation efficiency of 95.78%. Utilizing a unique bottom-superhydrophilic and top-hydrophobic structure, this composite aerogel demonstrates excellent salt resistance during continuous operation by preventing top precipitation and accelerating salt dissolution. Furthermore, SL acts as a protective layer and antioxidant, preventing H2O, O2, or free radicals from contacting MXene, passivating MXene defect sites, and consuming oxidation sources through reactions with H2O, O2, or free radicals. This significantly enhances the oxidative stability of MXene under exposure to air, light, humidity, and heat, thus ensuring the long-term operational stability of the composite aerogel.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A biomass / MXene composite aerogel, characterized in that, Including MXene, sodium lignosulfonate, and TEMPO oxidized nanocellulose; The biomass / MXene composite aerogel has a porous structure with vertically arranged channels, and one side of the surface perpendicular to the arranged channels is modified with polydimethylsiloxane. The preparation method of the biomass / MXene composite aerogel includes the following steps: (1) Sodium lignosulfonate and TEMPO oxidized cellulose nanosheets were added sequentially to the aqueous solution of MXene nanosheets, mixed evenly, and then a crosslinking agent was added. After mixing evenly again, a precursor solution was obtained. (2) The precursor solution was transferred to a container with a bottom heat-conducting and a perimeter heat-insulating structure and placed on the surface of the cryo-liquid for directional freezing. Then, it was freeze-dried to obtain the biomass / MXene composite aerogel precursor. The biomass / MXene composite aerogel precursor has a porous structure with vertically arranged channels. (3) Immerse the single-sided surface of the biomass / MXene composite aerogel precursor perpendicular to its internal channels in a polydimethylsiloxane solution and dry it to obtain the biomass / MXene composite aerogel. In step (1), the mass ratio of MXene to sodium lignosulfonate is (0.5~10):1; the mass ratio of MXene to TEMPO oxidized nanocellulose is (0.8~1.2):

1.

2. The biomass / MXene composite aerogel of claim 1, wherein, In step (1), the thickness of the MXene nanosheets is 2~5 nm; In step (1), the concentration of the MXene nanosheet aqueous solution is 5~6 g / L.

3. The biomass / MXene composite aerogel of claim 1, wherein, The crosslinking agent is silane coupling agent KH-560, and the mass ratio of MXene to silane coupling agent KH-560 is (0.5~1.5):

1.

4. The biomass / MXene composite aerogel of claim 1, wherein, In step (2), the cryosol is liquid nitrogen, and the directional freezing time is 10~20 min; In step (3), the polydimethylsiloxane solution is a polydimethylsiloxane-hexane solution, and the mass fraction of polydimethylsiloxane is 1%~3%; In step (3), the soaking time is 1~2 seconds.

5. The application of the biomass / MXene composite aerogel according to any one of claims 1-4 as a solar interface evaporator.

6. A solar interface evaporator, characterized in that, Includes the biomass / MXene composite aerogel as described in any one of claims 1-4.

7. The application of the solar interface evaporator as described in claim 6 in evaporation-induced power generation and solar thermal seawater desalination.

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