Photothermal--Magnetocaloric Coupled Evaporators for Self-Adaptive Water Evaporation and Oil--Water Purification in Complex Environments

Photothermal--Magnetocaloric Coupled Evaporators for Self-Adaptive Water Evaporation and Oil--Water Purification in Complex Environments | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 3 April 2026 V1 Latest version Share on Photothermal--Magnetocaloric Coupled Evaporators for Self-Adaptive Water Evaporation and Oil--Water Purification in Complex Environments Authors : Jingbo He , Dan Yang , Dongxue Wang , Chunyu Yang , Ruihan Guo , Mengshu Xu , Zhuoran Yang , Jian Huang , and Wei Guo 0000-0001-5445-7872 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.177522721.19127846/v1 177 views 109 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Solar-driven interfacial evaporation is a sustainable approach for freshwater production; however, its reliability is limited by the fluctuating solar intensity and complex water contaminants. This study produces a synergistic strategy that integrates magnetocaloric-mediated thermal compensation within a hierarchically structured aerogel. Iron-based nanoparticles derived from waste self-heating patches are incorporated into a konjac glucomannan/polyvinylpyrrolidone (KPF) aerogel with vertically aligned channels, yielding an adaptive photothermal–magnetocaloric coupled evaporation system capable of operating under diverse conditions. The KPF evaporator achieves an evaporation rate of 4.5 kg m -2 h -1 under one-sun illumination, increasing to 5.6 kg m -2 h -1 upon activation of an alternating magnetic field. Notably, under overcast and low-light conditions, comparable evaporation performance is maintained through magnetic-field-induced energy compensation. Molecular dynamics simulations and Raman spectroscopy reveals that magnetocaloric heating disrupts the ordered hydrogen-bond network of water, increasing the free water content and facilitating evaporation. The intrinsic underwater superoleophobicity of the KPF aerogel enables a coupled interception and evaporation mechanism for high-concentration oily wastewater, achieving a purification efficiency of 99.9%. Moreover, the magnetocaloric-enhanced Marangoni flow promotes salt ion migration, ensuring long-term stability in high-salinity environments. This dual-response strategy provides a universal platform for designing adaptive and efficient water treatment systems. Photothermal–Magnetocaloric Coupled Evaporators for Self-Adaptive Water Evaporation and Oil–Water Purification in Complex Environments Jingbo He, † Dan Yang, † Dongxue Wang, Chunyu Yang,* Ruihan Guo, Mengshu Xu, Dongxue Wang, Zhuoran Yang,* Jian Huang, Wei Guo* J. He, D. Yang, C. Yang, R. Guo, M. Xu, D. Wang, Z. Yang, J. Huang, W. Guo Key Laboratory of Photochemical Biomaterials and Energy Storage Materials, Heilongjiang Province and College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin, 150025, China E-mail: [email protected] Z. Yang, College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin, 150001, China Jingbo He and Dan Yang contributed equally to this work. Keywords: Solar-driven interface evaporation, photothermal–magnetocaloric coupling, self-adaptive evaporator, oil–water purification, self-cleaning capacity Abstract Solar-driven interfacial evaporation is a sustainable approach for freshwater production; however, its reliability is limited by the fluctuating solar intensity and complex water contaminants. This study produces a synergistic strategy that integrates magnetocaloric-mediated thermal compensation within a hierarchically structured aerogel. Iron-based nanoparticles derived from waste self-heating patches are incorporated into a konjac glucomannan/polyvinylpyrrolidone (KPF) aerogel with vertically aligned channels, yielding an adaptive photothermal–magnetocaloric coupled evaporation system capable of operating under diverse conditions. The KPF evaporator achieves an evaporation rate of 4.5 kg m -2 h -1 under one-sun illumination, increasing to 5.6 kg m -2 h -1 upon activation of an alternating magnetic field. Notably, under overcast and low-light conditions, comparable evaporation performance is maintained through magnetic-field-induced energy compensation. Molecular dynamics simulations and Raman spectroscopy reveals that magnetocaloric heating disrupts the ordered hydrogen-bond network of water, increasing the free water content and facilitating evaporation. The intrinsic underwater superoleophobicity of the KPF aerogel enables a coupled interception and evaporation mechanism for high-concentration oily wastewater, achieving a purification efficiency of 99.9%. Moreover, the magnetocaloric-enhanced Marangoni flow promotes salt ion migration, ensuring long-term stability in high-salinity environments. This dual-response strategy provides a universal platform for designing adaptive and efficient water treatment systems. 1. Introduction Global freshwater scarcity has become increasingly severe, particularly in arid and semi-arid regions, where an insufficient freshwater supply directly affects human life and environmental sustainability. [1,2] Under intensifying global climate change and water resource management challenges, traditional water treatment methods are now insufficient for meeting growing demand. Therefore, more efficient and environmentally friendly water purification technologies are urgently required. [3,4] Solar-driven interfacial evaporation (SDIE) has emerged as a promising green water treatment method in seawater desalination and wastewater treatment owing to its excellent solar-to-thermal conversion efficiency and environmental friendliness. [5-7] However, the SDIE technology faces several challenges in practical applications, particularly the instability of the evaporation flux under fluctuating natural light and complex water quality environments. [8-10] Moreover, the complex components in real water sources, such as emulsified oils and dissolved salts, cause pore clogging and salt crystallization, severely affecting the long-term stability of evaporators. [11,12] Therefore, the development of self-adaptive evaporators capable of functioning under all weather conditions and coping with complex water environments is crucial to achieve stable long-term freshwater production. [13] Among various materials, three-dimensional aerogels are ideal substrates for SDIE because of their ultralow density, high porosity, and customizable interconnecting channels. [14] This structure facilitates rapid capillary-driven water transport and has a low thermal conductivity that effectively prevents heat loss to the bulk water, enabling localized heat retention and improving evaporation efficiency. [15] Aerogel-based evaporators have been significantly improved in recent years. For example, Ma et al. proposed a three-dimensional aerogel evaporator that demonstrated excellent water transport and thermal localization capabilities through the synergistic effects of sodium alginate and reduced graphene oxide. [16] Additionally, Cao et al. employed a dual biomimetic strategy to design aerogel structures that combined efficient evaporation with exceptional antifouling abilities, demonstrating that fine surface engineering can impart superior antipollution properties to aerogels. [17] However, passive structural optimization alone is insufficient to achieve full-scene adaptability, in which the system autonomously adapts to low-light intensity, heavy oil pollution, and high-salinity conditions. Incorporating multisource energy compensation into aerogel frameworks has become critical for enhancing the performance of water evaporators. [18] Researchers have begun to explore external physical field regulation strategies to enhance the evaporation performance of aerogels. Among these, magnetic field control has gained attention as an innovative approach. [19] Direct current magnetic fields accelerate the migration of water molecules to the evaporation interface by weakening hydrogen bond stability, thereby enhancing evaporation rates. [20] However, alternating magnetic fields present unique advantages, such as a noncontact, fast response, and highly controllable thermal compensation mechanism. [21] Alternating magnetic fields can provide dynamic local heat supplementation through rapid magnetic field variations, enhancing the response speed and stability of the system under unstable light and extreme weather conditions. [22] This active heating mechanism compensates for energy shortages during cloudy days or at night while enhancing the thermodynamic behavior of interfacial water molecules. In complex water quality treatments, alternating magnetic fields accelerate the migration and discharge of salt ions, reduce the salt crystal accumulation, and prevent oil droplets from aggregating at the oil–wastewater interface. [23] Moreover, magnetocaloric effects regulate the structure of interfacial water molecules, enhancing water evaporation and significantly improving oil–water separation efficiency. In high-concentration oily emulsions, the “coupled interception-evaporation” mechanism enables the SDIE system to perform more stably and reliably under complex environmental conditions. In this study, we report a novel approach for integrating magnetocaloric effects into aerogel-based water evaporators to achieve a thermo-magnetically coupled evaporation system that enables the konjac glucomannan (KGM)/polyvinylpyrrolidone (PVP) water evaporator (denoted as KPF) to adapt comprehensively to complex multi-scenario environments ( Figure 1 ). Figure 1. Schematic illustration of the design of the photothermal–magnetocaloric coupled KPF evaporator and its self-adaptive application in enhanced solar-driven water evaporation. Through cross-linking-mediated interactions between KGM and PVP, we successfully constructed a vertically aligned layered microchannel aerogel network that ensured rapid water transport and structural stability. Furthermore, the powder recovered from the self-heating patches was converted in situ into Fe 3 O 4 nanoparticles, which were uniformly loaded onto the aerogel matrix, imparting broad-spectrum solar absorption and enhancing the magnetic responsiveness of the system. Under standard solar irradiation conditions, the system achieved an evaporation rate of 4.5 kg m -2 h -1 ; upon the introduction of an alternating magnetic field, the evaporation rate increased to 5.6 kg m -2 h -1 , showcasing the significant enhancement of evaporation performance by the magnetocaloric effect. More importantly, under cloudy or low-light conditions, the system maintained an evaporation performance comparable to that on sunny days through the energy compensation provided by the alternating magnetic field, demonstrating its remarkable adaptive response capability. Molecular dynamics (MD) and in situ Raman spectroscopy revealed that the magnetocaloric effect-induced temperature rise disrupted the highly ordered tetrahedral hydrogen bond network, increasing the proportion of free water and enhancing the water evaporation capacity. Additionally, the system utilizes a magnetocaloric-effect-enhanced Marangoni flow to accelerate the migration of salt ions, ensuring long-term stability in high-salinity environments. In complex oily wastewater, the KPF aerogel exhibited underwater superoleophobicity, enabling the “coupled interception and evaporation” mechanism and achieving a purification efficiency exceeding 99.9%. This synergistic strategy offers a universal paradigm for designing adaptive and efficient water treatment systems that operate effectively under complex environmental conditions. 2. Results and Discussion 2.1. Fabrication and Characterization of Various KPF Evaporators Initially, KGM was selected as the structural backbone for the aerogel, and PVP was introduced as a noncovalent crosslinking agent. This design leverages the abundant hydroxyl groups in KGM, which can spontaneously form intermolecular hydrogen bonds with the carbonyl groups in PVP under thermal induction. This facilitated the construction of a physically crosslinked network that ensured the mechanical strength and structural stability of the KPF evaporator. Additionally, during freeze-drying, the KGM–PVP matrix formed highly interconnected pores and continuous channels, providing a structural foundation for efficient water transport. To realize a synergistic photothermal–magnetocaloric evaporation system, a low-cost powder recovered from waste self-heating patches was incorporated as a functional additive. This powder, which contains iron-based components, undergoes carbonization to form iron oxides, imparting efficient solar absorption and heat generation capabilities under alternating magnetic fields. This powder was then uniformly dispersed in the KGM–PVP matrix via an in situ blending process. After freeze-drying and carbonization at 700 ℃, a lightweight, buoyant, and magnetically responsive KPF aerogel was obtained ( Figures 2a and 2b). Considering the prolonged operational requirements of an evaporator under continuous water immersion and solar irradiation, its mechanical properties were evaluated. Compressive tests revealed that, compared to that of the KGM+Fe 3 O 4 aerogel, the compressive strength of the KPF evaporator significantly improved with the incorporation of PVP. Furthermore, this property increased almost linearly with the amount of PVP added, allowing the aerogels (denoted as KPF-P x ) to withstand high compressive loads without structural failure. However, excessive PVP content (1.2 g) increased material stiffness, leading to premature fracture at lower strain levels, indicating that overcrosslinking impairs structural stability (Figure S1). Scanning electron microscopy (SEM) highlighted the impact of the PVP content on the internal structure (Figures 2c and S2). In the case of KPF-P 0.3 , insufficient crosslinking prevented the formation of ordered pore arrangements, whereas the excessive PVP content in KPF-P 1.2 induced over-crosslinking, resulting in a dense network structure that hindered pore connectivity. In contrast, at a PVP content of 0.6 g, KPF evaporators exhibited vertically aligned, interconnecting lamellar pore structures. This highly ordered pore architecture significantly reduced water transport path distortion and flow resistance, facilitating a rapid and continuous capillary-driven water supply. Elemental distribution analysis confirmed the homogeneous distribution of Fe, C, N, and O throughout the aerogel matrix (Figure 2d). X-ray photoelectron spectroscopy (XPS) was performed to elucidate the chemical composition and valence states of the KPF evaporator. The C 1s spectrum exhibited characteristic peaks at 284.8 eV (C-C), 285.9 eV (C-N), and 288.3 eV (C-O), primarily arising from the carbon backbone of KGM and PVP (Figure 2e). [24] In the Fe 2p spectrum, peaks at 711.3 eV and 724.8 eV were attributed to Fe 2+ , whereas those at 712.8 eV and 726.6 eV were assigned to Fe 3+ (Figure 2f). [25,26] The O 1s spectrum revealed peaks at 532.8 eV (C=O), 531.3 eV (C-O), and 530.1 eV (Fe-O), confirming the presence of Fe 3 O 4 (Figure S3). [27] Additionally, the N 1s spectrum exhibited peaks at 399.7 eV and 400.8 eV corresponding to pyrrole nitrogen and graphitic nitrogen, respectively (Figure S4). [28] We systematically investigated the effects of the powder content recovered from waste self-heating patches and carbonization temperature on the structure and performance of the aerogels (denoted as KPF-F x and KPF-x °C). The primary iron-containing phase in KPF-F 0.1 , KPF, KPF-F 0.4 , and KPF-500 °C was Fe 3 O 4 . However, at a carbonization temperature of 900 °C, a deep reduction reaction occurred, converting Fe 3 O 4 to Fe 3 C (Figures 2g and 2h). The SEM results show that as the filler content and carbonization temperature increased, the pore structure became more ordered (Figures S5 and S6). However, an excessively low filler content (KPF-F 0.1 ) or insufficient carbonization temperature (KPF-500 °C) resulted in underdeveloped pores, whereas excessive filler content (KPF-F 0.4 ) caused local pore blockage, and excessively high carbonization temperatures (KPF-900 °C) caused pore fragmentation, indicating that the structural integrity was compromised. All KPF evaporators demonstrated excellent hydrophilicity, with the KPF-900 °C sample exhibiting a slight decrease in wettability, owing to a higher degree of graphitization (Figures 2i and S7). Water transport experiments confirmed the exceptional water transport capacity of the KPF evaporators, as evidenced by the transport of red ink from the bottom to the top surface within 5 s (Figure S8). Moreover, the saturated water content of the KPF samples was significantly higher than that of the other samples, providing a continuous and sufficient water supply for evaporation (Figure S9). Differential scanning calorimetry (DSC) showed that KPF contained a higher proportion of free water, thereby reducing the energy required for the evaporation and resulting in the lowest equivalent evaporation enthalpy of 850.69 J g -1 (Figures 2j and 2k). This can be attributed to the ordered pore structure and moderate crosslinking, which weakened the interfacial interactions between water and matrix. Figure 2. (a) Schematic of the KPF evaporator preparation procedure. (b) Lightweight, floating, and magnetic properties; (c) cross-sectional SEM images; (d) EDS elemental mappings of C, N, O, and Fe; and (e) C 1s and (f) Fe 2p XPS spectra of the KPF evaporator. (g) XRD patterns of the KPF-series evaporators with varying Fe 3 O 4 contents. (h) XRD patterns of the KPF-series evaporators with varying carbonization temperatures. (i) Contact angle measurements, (j) DSC curves, and (k) water evaporation enthalpies of the KPF-series evaporators. (l) Evolution of IR images of the KPF-series dry evaporators with varying carbonization temperatures under one-sun illumination. (m) Magnetic hysteresis loops of the KPF-series evaporators with varying carbonization temperatures. (n) IR images of the KPF-series dry evaporators with varying carbonization temperatures under one-sun illumination and an alternating magnetic field. The KPF aerogels exhibited a significant light absorption capability across the solar spectrum (Figure S10). Under sunlight exposure, the KPF samples treated at various carbonization temperatures exhibited rapid photothermal responses. The surface temperature of the KPF increased from 22 °C to 52.3 °C within 5 s and stabilized at approximately 64.2 °C after 10 min (Figures 2l and S11). Hysteresis loop tests indicated that Fe 3 O 4 derived from the waste self-heating patches imparted excellent ferromagnetic properties to the KPF evaporator (Figure 2m). After the introduction of an alternating magnetic field, a synergistic photothermal–magnetocaloric system was established, resulting in a stepped increase in the thermal response. Under the same initial temperature, the surface temperature rapidly increased to 62.7 °C within 5 s and stabilized at an efficient evaporation temperature of 64.2 °C after 10 min (Figure 2n). Although the KPF-900 °C evaporator exhibited a stronger magnetic response, its magnetocaloric performance was inferior owing to high-temperature carbonization that converted Fe 3 O 4 into Fe 3 C. Although Fe 3 C and Fe 3 O 4 display superparamagnetic behavior and Fe 3 C exhibits higher saturation magnetization, its relaxation losses are constrained under an alternating magnetic field, resulting in a reduced magnetic-to-thermal energy conversion efficiency. [29] Compared to a single photothermally driven system, the KPF evaporator demonstrates superior photothermal conversion potential and possesses rapid magnetocaloric energy replenishment properties, which effectively compensate for heat deficiencies under overcast or low-light conditions, providing a reliable solution for stable and efficient water evaporation. 2.2 Magnetocaloric Effect Enhanced Water Evaporation Performance Evaluation of KPF Evaporators To assess the impact of the magnetocaloric effect on the water evaporation performance, we first evaluated KPF evaporators under non-magnetic conditions to provide a reference baseline for the subsequent performance enhancement under alternating magnetic fields. Under non-magnetic conditions, the surface temperature and water evaporation rates of KPF-P 0.3 , KPF, and KPF-P 1.2 were significantly higher than those of bulk water, with cumulative water mass losses reaching 3.83, 4.52, and 3.00 kg m -2 , respectively (Figure S12). Among these, the performance of KPF-P 0.3 was lower, likely due to its incomplete pore structure, whereas KPF-P 1.2 exhibited reduced performance because of the excessive accumulation of the crosslinking agent PVP in the pores, which hindered capillary-driven water transport. This initial evaluation under nonmagnetic conditions laid the foundation for subsequent magnetocaloric enhancement experiments, highlighting the importance of the pore structure and crosslinking degree in optimizing the evaporation performance. Further optimization of the loading of ferromagnetic Fe 3 O 4 particles and the annealing temperature of the aerogels revealed that KPF aerogels, prepared by adding 0.2 g Fe 3 O 4 and annealing at 700 °C, exhibited optimal evaporation performance. The water evaporation rate of KPF was 1.12, 1.37, 1.08, and 1.51 times higher than that of KPF-F 0.1 , KPF-F 0.4 , KPF-500 °C, and KPF-900 °C, respectively (Figures S13 and S14). To explore the effect of magnetocaloric heating, we compared the evaporation performances of KPF-series evaporators and established a solar interface water evaporation simulation system under alternating magnetic fields ( Figure 3a ). The alternating magnetic field generator comprised a programmable variable-frequency alternating current power supply and a one-dimensional circular Helmholtz coil. When the alternating current power was connected to the coil, a uniform and adjustable alternating magnetic field was generated within the central cavity of the coil. Finite element simulations (COMSOL) clearly depicted the magnetic field vector direction and highly uniform magnetic flux density contours at a field strength of 10 mT (Figures 3b and 3c). This precisely controlled magnetic environment provides a physical foundation for quantitatively studying the evaporation performance induced by the magnetocaloric effects. The alternating magnetic field had the most significant enhancement effect on the evaporation performance of KPF evaporators, where the interface temperature and evaporation performance increased by 1.39 and 1.23 times, respectively, outperforming other water evaporators (Figures 3d, 3e, and S15). Under an alternating magnetic field, Fe 3 O 4 particles generate a significant amount of heat through hysteresis losses. Owing to the moderate physical crosslinking density of KPF, this heat was efficiently and uniformly transferred to the surface of the water evaporator. In contrast, although KPF-900 °C exhibited higher magnetic induction, the relaxation losses of Fe 3 C formed at high temperatures limited the magnetocaloric conversion efficiency. Moreover, KPF reduced the resistance to water transport compared with KPF-F 0.4 , creating an efficient thermal exchange environment at the interface. Therefore, the KPF water evaporator demonstrated superior sensitivity relative to the other evaporators under alternating magnetic fields. As the magnetic field strength increased, the surface temperature and evaporation performance of the KPF evaporators increased linearly (Figures 3f, 3g, and S16). When the magnetic field strength increased from 4 mT to 10 mT, the surface temperature increased by 15.1 °C, 16.2 °C, 18.0 °C, and 20.4 °C, with evaporation rates of 4.69, 4.9, 5.16, and 5.6 kg m -2 h -1 , respectively. Under the same experimental conditions, the nonmagnetic KP evaporator showed no significant changes in surface temperature or evaporation performance. The introduction of ferromagnetic particles into a water evaporator structure plays a critical role in enabling energy conversion. To elucidate the mechanism underlying the enhancement of evaporation performance by the magnetocaloric effect, we conducted a coupled photothermal–magnetocaloric numerical simulation using COMSOL Multiphysics (Figures 3h). Under pure solar irradiation, the surface temperature of the KPF evaporator increased from 22.02 °C to 31.27 °C within 5 min. Upon introducing the alternating magnetic field, the surface temperature rapidly increased to 35.48 °C within 5 min, demonstrating a strong photothermal response. This indicates that the KPF evaporator exhibits exceptional sensitivity to an alternating magnetic field with nearly instantaneous energy conversion. The Fe 3 O 4 nanoparticles exhibited superparamagnetic behavior. Under an alternating magnetic field, heat generation does not originate from hysteresis loss but is instead dominated by relaxation losses, including the Néel and Brownian relaxation processes. In this process, the magnetic moments of single-domain nanoparticles are continuously reoriented in response to an external magnetic field, and the delayed relaxation of magnetization effectively dissipates the input electromagnetic energy as heat. [30] The localized heating effect causes a rapid increase in the surface temperature of the evaporator, significantly enhancing the evaporation efficiency. After 15 min, the temperature stabilized at approximately 41 °C, indicating the excellent thermal localization ability of the KPF aerogel, which effectively traps the generated heat at the evaporation interface rather than allowing it to dissipate into the bulk water. The simulations demonstrated a significant temperature increase, indicating that the additional thermal compensation generated by the magnetothermal effect effectively reduced the evaporation barrier of water molecules, enabling the KPF evaporator to retain high evaporation capability even under low-light or low-temperature conditions. Furthermore, at 0.5 and 0.75 sun intensities, the evaporation rate of the KPF evaporator decreased to 2.1 and 3.165 kg m -2 h -1 , respectively. However, the introduction of an alternating magnetic field significantly enhanced the evaporation rate to 3.05 and 4.27 kg m -2 h -1 , respectively, through the synergistic photothermal and magnetocaloric effects (Figure S17). As shown in Figure 3k, the KPF evaporator maintains superior evaporation performance under low-light conditions compared with other evaporators reported in the literature under the same conditions. [15,31-43] Finally, to validate the practical applicability of the photothermal and magnetocaloric effect enhancement strategies, we evaluated the evaporation performance of the KPF evaporator under alternating high- and low-light conditions in a simulated environment (Figure 3i). Under continuous one-sun illumination, the evaporation rate reached 4.52 kg m -2 h -1 , and after reducing the solar intensity, the rate dropped to 3.25 kg m -2 h -1 within 1 h (Figure 3j). Upon activating the alternating magnetic field, the evaporation rate increased immediately and approached that achieved under full sunlight irradiation. Therefore, the dual-response strategy effectively mitigates the issues arising from intermittent solar radiation and provides a new pathway for regulating the performance of KPF evaporators in complex natural environments. Figure 3. (a) Schematic of the alternating magnetic field generating device. (b) Magnetic field direction and (c) simulated magnetic field distribution of the one-dimensional circular Helmholtz coil. (d) Surface temperature evolutions and (e) time-dependent water mass of the KPF-series evaporators with varying Fe 3 O 4 contents and different carbonization temperatures under one-sun illumination and an alternating magnetic field. (f) Surface temperature evolutions and (g) water mass changes of the KP and KPF evaporators under one-sun illumination and an alternating magnetic field. (h) COMSOL simulation of surface temperature distribution of the KPF evaporator under one-sun illumination without and with an alternating magnetic field. (i) Schematics of evaporation under sunny, cloudy, and cloudy with an alternating magnetic field. (j) Evaporation rates of the KPF evaporator under alternating high- and low-light conditions in a simulated environment. (k) Comparison of evaporation rates of this work with previously reported systems. 2.3 Magnetocaloric Effect Enhanced Purification of Oil-in-Water Emulsions using KPF Evaporators To evaluate the purification performance of the KPF evaporator in treating oily wastewater, particularly in complex seawater environments, soybean oil, diesel, and engine oil were selected as three typical emulsified oils for a systematic study. In marine environments, oil leakages or spills often lead to the formation of stable oil-in-water emulsions. Owing to their small and well-dispersed oil droplets, these emulsions make separation and purification extremely challenging. To simulate this scenario, an ultrasonic method was used to introduce emulsifiers, prepare oil-in-water emulsions with an oil-to-water ratio of 1:100, and ensure stable dispersion of oil droplets. The evaporation rates of the KPF evaporators, evaluated under solar irradiation using soybean, diesel, and engine oil emulsions, showed evaporation rates of 4.45, 4.39, and 4.41 kg m -2 h -1 , respectively (Figure S18), which were almost identical to the evaporation rate in pure water, indicating that the KPF evaporator could effectively handle complex seawater environments containing emulsified oils. The evaporator demonstrated excellent structural resilience and antifouling abilities in moderately polluted seawater. However, extreme events such as oil spills can cause a sharp increase in localized oil concentrations. To assess the purification capability of the KPF evaporator in more challenging water bodies, the oil-to-water ratio was increased to prepare high-concentration oil emulsions in which the cumulative water mass losses for the KPF evaporator were 3.04 kg m -2 , 3.14 kg m -2 , and 2.98 kg m -2 , showing a slight performance decrease (Figure S19). An alternating magnetic field was introduced to enhance the purification performance of the evaporator under extreme conditions. Under a 10 mT alternating magnetic field, the solar steam generation rate significantly increased. The surface temperature of the KPF evaporator increased from 14.2 °C, 14.9 °C, and 15.31 °C in the absence of a magnetic field to 19.5 °C, 20.23 °C, and 20.9 °C, respectively. Correspondingly, the evaporation rates increased to 4.12, 4.21, and 4.05 kg m -2 h -1 , demonstrating the strong enhancement effect of magnetocaloric assistance on evaporation in complex, high-concentration oily water bodies ( Figures 4a and S19). After 15 testing cycles, the water evaporation performance showed no significant decline, demonstrating its excellent long-term stability under alternating magnetic fields and solar irradiation, even in high-concentration oil wastewater (Figure S20). The KPF evaporator combines magnetocaloric-assisted solar-driven interface evaporation with high-efficiency oil–water selective separation, enabling “coupled interception and evaporation” in complex oily water bodies. In this process, the magnetocaloric effect generated additional heat energy via the magnetic relaxation mechanism of the Fe 3 O 4 particles, thereby regulating the interfacial water structure during evaporation. Using in situ Raman spectroscopy, we monitored the evolution of the interfacial water molecular structure and hydrogen bond network during the temperature increase triggered by the magnetocaloric effect (Figures 4b, 4c, and S21). The O-H stretching vibration peaks in the 3000–3800 cm -1 range were deconvoluted into strong hydrogen-bonded (3200 cm -1 , four-coordinate network, highly ordered structure and constrained), weak hydrogen-bonded (3400 cm -1 , two-coordinate), and free water (3600 cm -1 , exhibiting the highest kinetic activity). [44] As the temperature increased, water molecules gradually escaped from the strong hydrogen-bonded network and transitioned to free water (free-H 2 O), with its proportion increasing from 10.3% to 37% (Figure 4d). This transition facilitates the evaporation of interfacial water molecules. The destruction of the hydrogen-bond network during this temperature increase caused a blue shift in the O-H stretching vibration band, indicating a decrease in 4-HB-H 2 O and an increase in free water, thereby creating favorable conditions for evaporation. [45,46] This structural change enables water molecules to escape more easily from the liquid phase, thereby enhancing the evaporation efficiency and highlighting the critical role of the magnetocaloric effect in the evaporation process. Furthermore, the KPF evaporator exhibited exceptional superhydrophilicity and underwater superoleophobicity, which enhanced its capability to handle complex oil–water mixtures (Figure 4e). The abundant hydrophilic groups on the lower surface of KPF (e.g., -C=O, -OH) formed strong hydrogen bonds with water molecules, promoting the rapid formation of a stable hydration layer on the surface, which prevented the aggregation of oil droplets (Figures S22 and 4f). This ensures that when oil droplets contact the evaporator surface, they do not penetrate the pores, but instead quickly roll off as spherical droplets, thereby preventing pore blockage and ensuring efficient evaporation. In addition, underwater oil contact angle (UOCA) tests showed that the KPF evaporator exhibited UOCA values > 150° for various oil pollutants, confirming its excellent underwater superoleophobicity (Figure 4g). This feature significantly improves the efficiency of oil–water separation. The “coupled interception and evaporation” mechanism effectively blocks the oil phase and promotes the permeation of the water phase, thereby ensuring efficient water evaporation. The oil–water separation mechanism can be further explained in terms of invasion pressure (ΔP). According to Laplace’s theory, when water contacts the lower surface of KPF, ΔP 0, effectively preventing oil penetrating (Figure 4h). [47,48] This physical barrier effect strongly supports the evaporation process, ensuring smooth penetration of water while blocking the oil phase and preventing interference with evaporation efficiency. The purification performance of the KPF evaporator toward oil-in-water emulsions was investigated under alternating magnetic fields, showing a significant improvement when treated water was compared with the original milky emulsion. After the solar-driven evaporation, the purified water became transparent, indicating the exceptional purification capability of the KPF evaporator (Figure 4i). Figure 4. (a) Surface temperature evolutions and evaporation rates of the KPF evaporator in different oil-in-seawater emulsions under one-sun illumination and generating magnetic field conditions. (b, c) Time-dependent in situ Raman spectra of O−H stretching vibrations. (d) Time-dependent quantitative proportions of three hydrogen-bonded water states. (e) Schematic of oil-repellent behavior. (f) The anti-oil contamination performance of the KPF evaporator. (g) UOCAs of different oil-in-seawater emulsions on the KPF evaporator surface. (h) Mechanistic model for selective oil rejection. (i) Photographs of various oil-in-water emulsions before and after purification. (j) TOC and removal efficiency for various emulsions under one-sun illumination and generating magnetic field conditions. (k) and (l) Excitation–emission–matrix spectra of motor-oil-contaminated seawater before and after purification. Subsequently, the total organic carbon (TOC) content and dissolved organic matter in the purified oil-contaminated seawater were analyzed using TOC analysis and three-dimensional fluorescence spectroscopy. After treatment with the KPF evaporator, the TOC content of the high-concentration oil-contaminated seawater was reduced by three orders of magnitude, corresponding to a purification efficiency exceeding 99.9% (Figure 4j). The fluorescence spectroscopy results indicated a significant decrease in the dissolved organic matter content of diesel-contaminated seawater after KPF treatment (Figures 4k and 4l). These findings confirmed that the KPF evaporator could effectively remove oil pollutants from seawater. By integrating photothermal effects, magnetocaloric effects, and underwater superoleophobicity, the KPF evaporator demonstrates efficient evaporation performance and maintains stable oil–water separation in complex environments. This strategy overcomes the application bottleneck of traditional evaporators in environments with high oil-to-water ratios, offering a new, efficient, and sustainable solution for treating seawater, oily wastewater, and other complex water bodies. 2.4 Magnetocaloric Effect-Enhanced Evaporation and Oil–Water Separation Mechanism in KPF Evaporators To evaluate the purification performance of the KPF evaporator in oil-contaminated wastewater, particularly in complex marine environments, we employed MD to systematically investigate the underlying mechanisms of the KPF evaporator in oil–water systems. Furthermore, this approach elucidates the molecular-scale behavior of the interfacial water evaporation process driven by the magnetocaloric effect. The models were constructed using a 1:25 oil-to-water volume ratio, featuring freely moving oil and water molecules, to simulate the evaporation process along the Z-axis. Molecular snapshots revealed that in the absence of the evaporator, the oil–water mixture remained in a disordered state. Although a few water molecules evaporated, the oil molecules either evaporated along with them or adhered to the interface, making effective separation impossible ( Figure 5a ). Upon introducing the KPF evaporator, the selective permeability became evident. Water molecules (red) were transported upwards through the pores and evaporated, whereas oil molecules (blue) were completely blocked beneath the KPF matrix (Figure 5b). This phenomenon confirms the superoleophobic underwater behavior and the Laplace pressure-blocking mechanism. When alternating magnetic fields were applied, the system exhibited significant kinetic enhancement. Under the same solar thermal conditions, the number of water molecules transitioning to vapor considerably increased in the system with a magnetic field of 10 mT (Figure 5c). At 1000 ps, the system with the magnetic field exhibited 81 evaporated water molecules compared to 43 in the system without the magnetic field, indicating an increase of approximately 45% in the water evaporation rate. The magnified image reveals that under the influence of magnetic heat, the water molecules at the interface have a higher kinetic energy, and the escape rate accelerates significantly. This increase in the number of evaporating water molecules can be attributed to the magnetic field elevating the surface temperature, which disrupts the hydrogen bonds between the water molecules, enhancing their mobility and making it easier for them to escape (Figure 5d). Crucially, despite the significant increase in the evaporation rate, oil molecule loss remained at zero, confirming that separation purity was not compromised by the magnetocaloric effect. The localized high temperature generated by the magnetic field helped maintain the dynamic hydration layer of the hydrophilic groups on the KPF surface, ensuring efficient water-oil separation. As shown in Figure 5e, the hydrogen bond density analysis indicates that the water-water hydrogen bond density at the aerogel-water interface is significantly lower than that in pure oil–water emulsions due to the hydrogen bond network formed between the KPF aerogel and water molecules, which weakens the inherent hydrogen bonding between the water molecules and enriches water molecules at the interface, thereby reducing the evaporation enthalpy of water. Figure 5. MD simulations of evaporation behavior in complex oil–water emulsions. Oil–water mixture (a) without the KPF evaporator or an alternating magnetic field, (b) with the KPF evaporator but without an alternating magnetic field, And (c) with the KPF evaporator under an alternating magnetic field. (d) Number of evaporated water molecules along the Z-axis, (e) time-dependent variations in the number of hydrogen bonds and (f) MSD curves of water molecules in three different systems. The slope of the mean squared displacement (MSD) curve showed a notable increase, indicating that the introduction of the KPF evaporator significantly enhanced the diffusivity of water molecules (Figure 5f). These results collectively confirm that under the same energy input, the KPF evaporator significantly strengthens the evaporation process of water molecules in complex oil systems while efficiently suppressing the migration of oil molecules into the vapor phase, demonstrating excellent synergistic oil–water separation and enhanced evaporation performance. Further analysis revealed that the number of hydrogen bonds within the system decreased significantly under the influence of the magnetic field, resulting in weakened intermolecular constraints. This reduction in molecular interactions creates favorable conditions for the evaporation of water molecules. Although physical coverage by oil droplets can increase the resistance to water molecule transport during the treatment of high-concentration oily wastewater, the localized heat generated by the magnetocaloric effect imparts higher random motion energy to the water molecules. This led to a notable increase in the slope of the MSD curve, which confirmed a significant enhancement in the mobility of the water molecules. The underlying mechanism behind this phenomenon is the induction of the magnetocaloric effect by an applied alternating magnetic field, which increases the temperature at the interface. The increased surface temperature disrupts the hydrogen bond network between the water molecules, weakening their cohesive forces and lowering the energy barrier for evaporation. This process effectively accelerates the bulk evaporation of water molecules, facilitating more efficient water separation from the oil phase. 2.5 Adaptive Performance of KPF Evaporators under Variable Climatic Conditions for Seawater Desalination When addressing the challenges of treating high-concentration oily wastewater, the long-term operation of the system in seawater, where the prevention of salt crystallization is essential for maintaining efficient evaporation, must be considered. To systematically evaluate the desalination performance of the KPF evaporator, this study utilized seawater from the Bohai Sea in China as the evaporation medium and monitored its steam generation under solar irradiation. The KPF evaporator exhibited excellent evaporation stability, achieving an evaporation rate of 4.42 kg m -2 h -1 , comparable to that of pure water, with no observable salt crystallization on the evaporator surface (Figures 6a, 6b, and S23). When a 10 mT alternating magnetic field was introduced, the seawater evaporation rate increased to 5.48 kg m -2 h -1 , with the evaporator surface temperature rising from 34.67 °C to 40.17 °C, confirming the significant contribution of the magnetocaloric effect to seawater evaporation. Quantitative analysis of Na⁺, K⁺, Ca 2+ , and Mg 2+ in the condensed water revealed that their concentrations were significantly below the drinking water quality standards set by the World Health Organization, confirming the outstanding desalination performance of the KPF evaporator (Figure 6c). [49] To investigate its superior self-cleaning capability, the dissolution of a constant mass of NaCl crystals on the KPF surface was monitored using digital and optical microscopy. Under dark conditions, substantial amounts of salt residue remained after 45 min. Under one-sun illumination, the salt particles dissolved significantly, thereby exposing the black evaporator to the substrate. Notably, with the auxiliary 10 mT alternating magnetic field, most salt crystals were completely dissolved within the same timeframe (Figures 6d and S24). These findings indicate that introducing an alternating magnetic field significantly accelerates the salt dissolution kinetics and enhances the self-cleaning capacity, providing a critical safeguard for the stable, long-term operation of the KPF evaporator in hypersaline environments. Figure 6e shows the adaptive salinity regulation mechanism of the KPF evaporator, highlighting the enhancement of the Marangoni effect through the magnetocaloric effects. [50] The unique porous structure of the KPF evaporator generates capillary suction, which enables continuous water pumping. Under light exposure, water molecules escape, creating a localized high-salinity region at the evaporation interface. This results in the establishment of a significant concentration gradient between the evaporation surface and water transport channel. The introduction of the magnetocaloric effect accelerated the evaporation dynamics and strengthened the driving force of the concentration gradient. With increasing salt ion concentration, the surface tension of the water increased, leading to the formation of a high-surface-tension zone at the evaporation interface. This change triggers a Marangoni flow, in which the liquid moves from the low-salinity region to the high-salinity region. [50] When rapid adjustment is required, the introduction of an alternating magnetic field enhances the flow and facilitates the migration of water molecules. In synergy with the capillary action, this process drives water toward the core region of the evaporator. Ultimately, a compensatory flow is generated that continuously dissolves and transports the salt ions deposited in the evaporation zone back into the bulk water phase, thereby preventing salt accumulation on the evaporator surface. Through this adaptive salinity regulation mechanism, the KPF evaporator maintained a salt-free surface, thereby achieving a self-cleaning function and ensuring that salt deposition did not interfere with the long-term performance of the evaporator. To validate the feasibility of the KPF evaporator under dynamic climatic conditions, a solar-driven outdoor experimental system integrating an alternating magnetic field was developed (Figure S25). This system integrates solar photovoltaic panels for energy storage, ensuring stable operation of the alternating magnetic field device under insufficient sunlight. The environmental temperature, relative humidity, solar irradiance, evaporator surface temperature fluctuations, and changes in water mass were continuously monitored from 8 AM to 6 PM on sunny and cloudy days during the same season. This system was used to assess the adaptive capability of magnetocaloric effects in response to environmental fluctuations. Under sunny conditions, the peak surface temperature of the evaporator reached 43.1 °C, with a maximum evaporation rate of 6.19 kg m -2 h -1 (Figures 6f and 6g). Under cloudy conditions, where solar irradiance drastically decreased, activating the alternating magnetic field effectively provided thermal compensation, increasing the surface temperature to 41.7 °C. The evaporation rate increased from 4.2 to 5.69 kg m -2 h -1 , successfully matching the performance observed on sunny days (Figures 6h, 6i, and S26). Both scenarios met the daily drinking water requirements of a five-person household for six days. [51] Figure 6. (a) Surface temperature variations and (b) evaporation rates of the KPF evaporator under one-sun irradiation with and without an alternating magnetic field. (c) Ion concentrations in raw seawater and KPF-collected freshwater. (d) Optical and microscopic images showing the salt resistance behavior of the KPF evaporator under one-sun irradiation with and without an alternating magnetic field. (e) Schematic of the salt rejection behavior under the Marangoni effect enhanced by an alternating magnetic field. Variations in (f) ambient temperature and relative humidity and (g) evaporator surface temperature, sunlight intensity, and evaporation rates from 8 AM to 6 PM on a sunny day. Variations in (h) ambient temperature and relative humidity from 8 AM to 6 PM on a cloudy day and (i) evaporator surface temperature, solar intensity, and evaporation rates from 8 AM to 6 PM on a cloudy day with an alternating magnetic field. (j) Images and (k) germination rate of mung bean seeds irrigated with seawater, tap water, distilled water, and KPF-desalinated water. Furthermore, to assess the biological safety of the desalinated water, a mung bean germination experiment was performed because mung beans are highly sensitive to water salinity. Seawater failed to support germination because of high salt concentrations. However, mung beans soaked in desalinated water achieved 100% germination within 48 h, and the growth morphology of the sprouts was superior to that observed in the tap and distilled water control groups (Figures 6j and 6k). This provides strong evidence that desalination systems have great potential for addressing freshwater shortages, overcoming the limitations imposed by extreme weather conditions, and meeting agricultural irrigation requirements. 3. Conclusion In summary, this study presents a self-adaptive SDIE evaporation system enabled by photothermal–magnetocaloric coupling within a hierarchically structured aerogel. By introducing an actively tunable magnetocaloric thermal compensation pathway, the evaporator overcomes the intrinsic dependence of conventional photothermal systems on stable solar irradiation, thereby achieving robust operation under fluctuating light and complex water conditions. The coupled energy-field strategy allows dynamic regulation of the interfacial temperature and water molecular behavior. Magnetocaloric heating supplements insufficient solar input and disrupts the interfacial hydrogen-bond network, thereby reducing the kinetic constraints on water evaporation. Furthermore, the intrinsic underwater superoleophobicity of the aerogel establishes a coupled interception–evaporation mechanism that effectively decouples water vapor generation from oil contamination. The magnetocaloric-enhanced Marangoni flow further enables adaptive salinity regulation, prevents salt accumulation, and ensures long-term operational stability. Overall, we propose a generalizable design paradigm for adaptive water treatment systems in which multi-energy-field coupling is employed to actively manipulate the interfacial thermodynamics and mass transport. By integrating photothermal conversion, magnetic regulation, and interfacial water chemistry, this study provides new insights for the development of resilient freshwater production and wastewater purification technologies in real-world environments. 4. Experimental Methods Materials : KGM and PVP were obtained from Macklin and Aladdin, respectively. Sodium dodecyl sulfate (SDS, 99.9%) and NaCl were purchased from Innochem. All reagents mentioned were of analytical grade and were used without further purification throughout the experiment. Natural seawater was collected from the Bohai Bay in Liaoning Province (China). Mung bean seeds, soybean oil, motor oil, and diesel were all purchased from a local supermarket. The discarded self-heating patches were collected from commercially available self-heating patches that had been used in daily life. Preparation of various KPF aerogel evaporators : To prepare the KPF aerogels, 1.2 g of KGM was dissolved in 60 mL of deionized water and heated in a water bath while stirring continuously at 60 °C for 30 min. Next, 0.6 g of PVP was added to the mixture, and stirring continued for another 30 min to form a hydrogel matrix. Then, 0.15 g of waste thermal paste was introduced, and stirring continued for an additional 30 min to ensure uniform dispersion. The discarded thermal paste powder was thoroughly washed with deionized water to remove impurities, followed by drying at 60 °C for 24 h. The resulting mixture was poured into molds and subjected to static gelation at -4 °C, followed by overnight freezing at -20 °C to form a crosslinked hydrogel. The gelled samples were then freeze-dried to create the precursor aerogels. The obtained precursor aerogels were calcined at 700 °C for 2 h under an argon atmosphere to obtain the final product, termed KPF. Other KPF series water evaporators with different experimental variables are labeled as KPF-X a , where “X” represents the controlled experimental variable, and “a” indicates the specific dosage of the corresponding component. For KPF with varying amounts of PVP, the samples are named KPF-P 0.3 and KPF-P 1.2 . For KPF with varying amounts of thermal paste, they are labeled KPF-F 0.1 and KPF-F 0.4 . For KPF with varying carbonization temperatures, they are named KPF-500 °C and KPF-900 °C. Characterization : The surface morphology and microstructure of aerogel evaporators were observed by a scanning electron microscope (SEM, S-4800, Hitachi). The elemental distribution of the materials was analyzed using energy dispersive spectroscopy (EDS, Gemini Sigma 300, Germany). The crystalline structures and chemical compositions of evaporators were determined by X-ray diffraction spectroscopy (XRD, Bruker AXS D8 Advance), X-ray photoelectron spectroscopy (XPS, Kratos Axis Ultra DLD), and Fourier transform infrared spectrometer (FTIR, Nicolet 6700, Thermo Electron). UV–Vis–NIR diffuse reflectance spectra were acquired using a Hitachi U-4100 spectrophotometer, while Raman spectra were measured using a laser confocal Raman spectrometer. A vibrating sample magnetometer (Lake Shore 7410) was employed to analyze the magnetic properties of the samples, whereas a universal testing machine (TSE 104B) was utilized for the measurement of compressive strength. The contact angles were probed with a contact angle goniometer (OCA 15 machine, Data-Physics, Germany). A contact angle measurement system (JC2000D4) was employed to determine water/oil contact-angle measurements. A solar power meter (FZ 400) was used to calibrate the illumination intensity of the Xe lamp, whereas the surface temperatures of the evaporators were monitored using an infrared thermal camera (FLIR E6). In situ Raman spectroscopy (TSG100-0) was employed to monitor variations in the hydrogen bond structures of water molecules during the evaporation process. The vaporization enthalpy of aerogels was measured on a differential scanning calorimeter (DSC, PerkinElmer DSC8500). The organic matter concentrations in the oil-in-water (O/W) emulsions before and after purification were determined using a total organic carbon (TOC) analyzer (TOC-VCPH, Shimadzu, Kyoto, Japan), and the total luminescence spectra before and after purification were measured with a fluorescence spectrophotometer (Hitachi F-7000, Hitachi High-Technologies Corporation, Japan). The concentration of ions was measured by inductively coupled plasma mass spectrometry (ICP-MS). Solar vapor generation experiments : The KPF evaporator was placed on a hollow low-thermal-conductivity polystyrene foam board, and then floated on the seawater within a beaker. A xenon lamp (HSX-F300) was used to simulate sunlight, with the light intensity regulated to 1 kW m -2 (standard solar irradiance) using a solar power meter (FZ 400). The entire evaporation device was placed on an electronic balance (BSA 124S) with an accuracy of 0.0001 g, and the mass loss of water was continuously measured for 1 h, with data recorded every 5 min. Meanwhile, an infrared thermal imager was used to monitor the temperature changes on the surface of the evaporator in real time. To eliminate interference from environmental factors, the dark evaporation rate of each sample was measured for 1 h under light-free conditions. This dark evaporation rate was then subtracted from the evaporation rate under illumination to obtain the net evaporation rate driven exclusively by solar energy. For the alternating magnetic field-assisted evaporation experiment, the evaporation device was placed in the cavity of a Helmholtz coil, maintaining the same test conditions as the photothermal evaporation. The mass loss of water was quantitatively measured within 60 min to evaluate the regulatory effect of the alternating magnetic field on the evaporation performance. COMSOL Multiphysics temperature distribution simulation : This study employs a solid-fluid heat transfer module and an electromagnetic thermal module to couple and describe the entire process of heat transfer and temperature distribution around the KPF evaporator under two operating conditions: sole solar thermal irradiation and the coupled action of solar thermal and magnetic thermal fields. An external light source simulates solar irradiation via a light beam heating model. The fundamental heat transfer equations are presented as follows: Heat transfer module: where ρ is the material density (1100 kg m -3 ), Cp (3000 J kg -1 K -1 ) is the specific heat capacity of the material, u is the spatial fluid velocity field, T is the temperature, q is the heat flux, Q is the heat source power, and k is the thermal conductivity of the material (0.05 W m -1 K -1 ). In this study, the fluid velocity is set to 0. Current Module: J denotes the current density, Q j, v represents the volumetric charge density, E refers to the spatial electric field, Je stands for the current density induced by the external current source, V is the electric potential, and δ is the electrical conductivity of the material (0.0005 S m -1 ). The boundary condition is specified as a linear time-varying voltage, with the voltage set at 58 V. The electro-thermal modules are coupled via the Joule heating effect: Q e denotes the Joule heating power. MD simulation of the water evaporation : For this study, PACKMOL was used to generate molecular simulation models. Before conducting molecular dynamics (MD) simulations, the entire system was subjected to energy minimization via the conjugate gradient algorithm. The purpose of this step was to eliminate unfavorable atomic contacts, optimize the initial configuration, and effectively reduce the system potential energy. Regarding force field settings, water molecules were described using the SPC/E model, while oil components were parameterized with the OPLS-AA force field. The detailed model construction workflow and parameter settings are as follows: Model 1 was constructed for a water-diesel system with a volume ratio of 1:25. To avoid non-physical interactions along the z-direction and simulate an open interfacial environment, a 10 nm vacuum layer was introduced above the water-diesel interface. Building on Model 1, Model 2 was developed by incorporating a Fe 3 O 4 -loaded carbon network structure into the water-oil mixture system. Consistent with Model 1, a 10 nm vacuum layer was also added to the system to ensure interfacial integrity and stability during subsequent MD simulations. Model 3 was further established based on Model 2 by introducing an alternating magnetic field, aiming to simulate the effect of the magnetic field on water molecule evaporation. All simulations were performed in the NVT ensemble, with temperature regulated using a Nosé-Hoover thermostat. An integration time step of 1 fs was adopted, and long-range electrostatic interactions were handled via the particle-particle particle-mesh (PPPM) method. The purification experiment of oil-in-water emulsion : Soybean oil, diesel oil, and motor oil were separately mixed with seawater at volume ratios of 1:100 and 1:25, respectively. Then, 2 g·L -1 SDS was added to each mixture, which was sonicated in an ultrasonic homogenizer for 30 min to prepare uniformly dispersed oil-in-water emulsions. The KPF aerogel evaporator was placed in these prepared emulsions to conduct the evaporation purification experiment. The experiment was carried out in a self-made quartz container; the container wall was designed with an inclination to guide condensed water vapor into the front-end collection device. Each evaporation purification experiment for the oil-water emulsion was repeated three times to ensure the reliability of the results. Desalination tests : Using real seawater collected from the Bohai Bay in Liaoning Province, China, as the experimental medium, the KPF evaporator was floated on the seawater surface and placed in a self-made quartz container to conduct the water purification, collection, and experiment. The container wall was designed with a tilt, which could enable the condensed water vapor to flow into the front-end collection device. The cold condensed water was tested by inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentrations of four major ions, namely Na⁺, K⁺, Mg 2+ , and Ca 2+ . Additionally, 0.5 g of NaCl was placed on the surface of the KPF evaporator, and the salt dissolution behavior was observed and compared under three conditions: darkness, one-sun irradiation, and an alternating magnetic field assistance within 60 min. Outdoor evaporation and seed germination experiments : The KPF evaporator was placed in a custom-fabricated large-scale quartz integrated evaporation and collection device, and outdoor evaporation experiments were conducted on sunny and cloudy days, respectively. Environmental parameters, including temperature, relative humidity, and solar irradiance, were systematically recorded throughout the experiments, along with the evaporator surface temperature and water production rate. For the cloudy-day tests, an alternating magnetic field apparatus was integrated into the experimental setup to investigate its auxiliary enhancement effect on evaporation. Additionally, germination experiments were performed using mung bean seeds with four types of water samples: the collected condensate, natural seawater, tap water, and distilled water. The germination rate and growth characteristics of the mung bean seeds were then compared over 48 h. Acknowledgements This work was supported by Heilongjiang Provincial Natural Science Foundation of China (PL2024B004), the Scientific Innovation Project for Harbin Normal University (HSDSSCX2025-24) , and Heilongjiang Provincial Training Program of Innovation for Undergraduates (S202510231167) . 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Keywords carbon materials clean water desalination porous materials waste water treatment Authors Affiliations Jingbo He Harbin Normal University View all articles by this author Dan Yang Harbin Normal University View all articles by this author Dongxue Wang Harbin Normal University View all articles by this author Chunyu Yang Harbin Normal University View all articles by this author Ruihan Guo Harbin Normal University View all articles by this author Mengshu Xu Harbin Normal University View all articles by this author Zhuoran Yang Haerbin Engineering University View all articles by this author Jian Huang Harbin Normal University View all articles by this author Wei Guo 0000-0001-5445-7872 [email protected] Harbin Normal University View all articles by this author Metrics & Citations Metrics Article Usage 177 views 109 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Jingbo He, Dan Yang, Dongxue Wang, et al. Photothermal--Magnetocaloric Coupled Evaporators for Self-Adaptive Water Evaporation and Oil--Water Purification in Complex Environments. Authorea . 03 April 2026. DOI: https://doi.org/10.22541/au.177522721.19127846/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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