Chitosan assisted MXene decoration onto polymer fabric for high efficiency solar driven interfacial evaporation of oil contaminated seawater

Mechanically robust and electrically conductive nanofiber composites with enhanced interfacial interaction for strain sensing

Electrically conductive fiberfibre/fabric composites (ECFCs) are competitive candidates for use in wearable electronics. Therefore, it is essential to develop mechanically robust ECFC strain sensors with sensing performance. In this study, MXene assembly and hot-pressing were combined to prepare strong yet breathable ECFCs for strain and temperature sensing. Hydrogen bonding between MXene and polyurethane (PU) and ultrasonication-induced interfacial sintering were responsible for MXene nanosheets assembly on the PU nanofibers. MXene decoration made PU nanofibers electrically conductive, resulting in a conductive network. Hot-pressing improved interface adhesion among the conductive nanofibers. Thus, the mechanical properties of the nanofiber composites, including tensile strength, toughness and fracture energy, were enhanced. The nanofiber composites exhibited surface stability and durability. When the nanofiber composites were used as strain sensors, they showed breathability with a linear resistance response ranging from 1 % to 100 % and cycling stability. In addition, they produced stable sensing signals over 1000 cycles when a notch was present. They could also monitor temperature variations with a negative temperature coefficient (-0.146 %/°C). This study provides an interfacial regulation method for the preparation of multi-functional nanofiber composites with potential applications in flexible and wearable electronics.

Group-IIIA element doped BaSnS2 as a high efficiency absorber for intermediate band solar cell from a first-principles insight

The quest for high-performance solar cell absorbers has garnered significant attention in the field of photovoltaic research in recent years. To overcome the Shockley-Queisser (SQ) limit of ∼31% for single junction solar cell and realize higher power conversion efficiency, the concept of an intermediate band solar cell (IBSC) has been proposed. This involves the incorporation of an intermediate band (IB) to assist the three band-edge absorptions within the single absorber layer. BaSnS2 has an appropriate width of its forbidden gap in order to host an IB. In this work, doping of BaSnS2 was studied based on hybrid functional calculations. The results demonstrated that isolated and half-filled IBs were generated with suitable energy states in the band gap region after group-IIIA element (i.e., Al, Ga, and In) doping at Sn site. The theoretical efficiencies under one sun illumination of 39.0%, 44.3%, and 39.7% were obtained for 25% doping concentration of Al, Ga, and In, respectively; thus, larger than the single-junction SQ-limit. Furthermore, the dopants have lower formation energies when substituting the Sn site compare to occupying the Ba and S sites, and that helps realizing a proper IB with three band-edge absorptions. Therefore, group-IIIA element doped BaSnS2 is proposed as a high-efficiency absorber for IBSC.

Polydopamine/Fe3O4 modified wood-based evaporator for efficient and continuous water purification

Solar interfacial evaporation is a highly promising technology for seawater desalination and wastewater treatment, while the simple preparation processes and efficient production of clean water based on biomass interfacial evaporators still need further exploration and development. Here, we reported a wood-based evaporator (PFDW) loaded with Fe3O4 and polydopamine (PDA) after simple immersion treatment at room temperature for efficient and continuous water purification. The synergistic photothermal effect of PDA coating and Fe3O4 particles enables the evaporator to achieve high photothermal conversion efficiency in the longer wavelength range, while combined with the rapid water transport capacity endowed by the vertically aligned microporous structure of natural wood, it achieved an evaporation rate of 1.70 kg m-2h-1 and an energy efficiency of 98.0% under 1 kW m-2 irradiation. In addition, the prepared PFDW exhibited sustainable desalination stability and excellent removal efficiency for different water sources including organic dye wastewater, heavy metal effluent, oil-water emulsion and river water. This work provides a new avenue for efficient salt-tolerant portable evaporators.

Hierarchical nanofibrous and recyclable membrane with unidirectional water-transport effect for efficient solar-driven interfacial evaporation

Solar-driven interfacial evaporation technology has attracted significant attention for water purification. However, design and fabrication of solar-driven evaporator with cost-effective, excellent capability and large-scale production remains challenging. In this study, inspired by plant transpiration, a tri-layered hierarchical nanofibrous photothermal membrane (HNPM) with a unidirectional water transport effect was designed and prepared via electrospinning for efficient solar-driven interfacial evaporation. The synergistic effect of the hierarchical hydrophilic-hydrophobic structure and the self-pumping effect endowed the HNPM with unidirectional water transport properties. The HNPM could unidirectionally drive water from the hydrophobic layer to the hydrophilic layer within 2.5 s and prevent reverse water penetration. With this unique property, the HNPM was coupled with a water supply component and thermal insulator to assemble a self-floating evaporator for water desalination. Under 1 sun illumination, the water evaporation rates of the designed evaporator with HNPM in pure water and dyed wastewater reached 1.44 and 1.78 kg·m-2·h-1, respectively. The evaporator could achieve evaporation of 11.04 kg·m-2 in 10 h under outdoor solar conditions. Moreover, the tri-layered HNPM exhibited outstanding flexibility and recyclability. Our bionic hydrophobic-to-hydrophilic structure endowed the solar-driven evaporator with capillary wicking and transpiration effects, which provides a rational design and optimization for efficient solar-driven applications.

Removal and reuse of heavy metal ions on mildly oxidized Ti3C2 @BF membrane via synergistic photocatalytic-photothermal approach

The pollution of heavy metal ions in water seriously affects the ecosystem and human health. Here, an efficient synergetic photocatalytic-photothermal system is designed by combining a mildly oxidized Ti3C2 (mo-Ti3C2) with a super hydrophilic bamboo fiber (BF) membrane. The mo-Ti3C2 heterojunction promotes the transfer and separation of photoinduced charges and thus enhances the photocatalytic reduction of heavy metal ions (Co2+, Pb2+, Zn2+, Mn2+ and Cu2+). The photoreduced metal nanoparticles with high conductivity and LSPR effect further accelerate the transfer and separation of photoinduced charges, and improve photothermal and evaporative performance. The mo-Ti3C2-2.4 @BF membrane in Co(NO3)2 solution can achieve an excellent evaporation rate of 4.6 kg·m-2·h-1 and a high solar-vapor efficiency of up to 97.5% under the light intensity of 2.44 kW·m-2, which are 27.8% and 19.6% higher than those in H2O, respectively, demonstrating the reuse of photoreduced Co nanoparticles. No heavy metal ions are detected in any of the condensed water, and the Co2+ removal rate in the concentrated Co(NO3)2 solution is up to 80.4%. The synergetic photocatalytic-photothermal approach on the mo-Ti3C2 @BF membrane provides a new scope for the continuous removal and reuse of heavy metal ions, as well as for obtaining clean water.

Carbon nanofiber reinforced carbon aerogels for steam generation: Synergy of solar driven interface evaporation and side wall induced natural evaporation

Solar-based interface evaporation (SIE) is a green, efficient and cost-effective technique to harvest fresh water. 3D solar evaporators show their unique advantages in gaining energy from environment and hence possess a higher evaporation rate than 2D evaporators. However, much effort is still required to develop mechanically robust and superhydrophilic 3D evaporators with strong water transportation capability and salt-rejection performance, and at the same time reveal how they gain energy from environment via the natural evaporation. In this work, a novel carbon nanofiber reinforced carbon aerogel (CNFA) is prepared for the SIE. The CNFA has a high light absorption up to 97.2% and outstanding photothermal conversion performance. The heteroatom doping and hierarchically porous structure endow the CNFA with superhydrophilicity and thus powerful water transportation capability and salt rejection performance. Benefiting from synergy of the SIE and side wall induced natural evaporation, the CNFA evaporator exhibits a high evaporation rate and efficiency (as high as 3.82 kg m^-2h^-1 and 95.5%, respectively) with long-term stability and durability. The CNFA can also work normally in high-salinity and corrosive seawater. This study demonstrates a new method to fabricate all-carbon aerogel solar evaporators and provides insights for the effective thermal management during the interface evaporation.

Stretchable, durable and asymmetrically wettable nanofiber composites with unidirectional water transportation capability for temperature sensing

The one-way transportation of liquids plays an important role in smart and wearable electronics. Here, we report an asymmetric nanofibrous membrane (ANM) with unidirectional water transport (UWT) capability by integrating one superhydrophilic MXene/Chitosan/Polyurethane (PU) nanofiber membrane (MCPNM) and one ultrathin hydrophobic PU/Polyvinylpyrrolidone (PVP) layer with a "bead-on-string" structure. The UWT performance shows long-term stability and can be well maintained during the cyclic stretching, abrasion and ultrasonic washing tests. The ANM exhibits negative temperature coefficient and is served as a temperature sensor to monitor the temperature variation of the environment, which can provide efficient alarm signals in a hot or cold condition. When attached on person's skin, the ANM displays a unique anti-gravity UWT behavior. The stretchable, wearable and multi-functional nanofibrous composite membrane with an asymmetric wettability shows potential applications in flexible and wearable electronics, health monitoring, etc.

Potential of MXene-based membranes in water treatment and desalination: A critical review

MXenes have emerged as wonderful materials that earned enormous attention in the last decade for applications in various fields. The potential of MXenes in the development of novel membranes has been explored recently by many researchers. This review critically assessed the recent advances in applications of MXene-based materials for the development of novel membranes. The synthesis routes of the MXene-based membranes are discussed, and the applications of developed membranes in water treatment and desalination are elaborated in detail. MXene-based membranes have demonstrated excellent potential in water treatment and desalination for the removal of dyes, metal ions, and salts from water. These membranes have unveiled exceptional antifouling potential and were proven to be a good choice to be employed in oil/water (O/W) separation. Besides impressive progress, numerous barriers restrict the practical applications of these membranes. The challenges related to synthesis routes of MXenes and MXene-based membranes, their stability and reusability potential, and the development of membranes on large scale are highlighted. Finally, recommendations for future work are suggested to overcome these limitations in future.