Research Article Issue
Four-birds-with-one-stone: A multifunctional Ti-based material for solar-driven water evaporation
Nano Research 2024, 17 (5): 4498-4506
Published: 24 November 2023

Sustainable, environmentally friendly and low-energy desalination materials have important research value for the increasing demand of freshwater year by year. However, it is a huge challenge to maintain high heat energy transfer efficiency without reducing the heat conversion capacity of specific solar photothermal conversion materials. Moreover, their efficiency and durability are greatly limited by the problems of seawater corrosion, oil, and bacteria pollutions. Till now, no related work has been reported to solve all the aforementioned problems via a simple four-birds-with-one-stone strategy. Herein, a class of multifunctional porous photothermal silver (Ag) modified Ti foams (Tf-TA/Ag series materials) is prepared for the development of advanced solar water evaporation devices, and provides alternative materials for alleviating freshwater crisis and treating sewage. The oil contact angle (OCA) changes from 41° to 180°, which significantly reduces the adhesion of oil. In addition, Tf-TA2/Ag sample also shows an excellent and sustained antibacterial effect, which maintains above 99.9% of antibacterial rate after repeated 5 times. The surface temperature of the Tf-TA2/Ag sample reaches 52.5 °C after simulated sun irradiation for 20 min, which is significantly higher than that of the contact groups (water: 36.4 °C, Ti foam: 38.2 °C and Tf-TA2: 40.9 °C). The capacity of seawater evaporation and salt removal is enhanced due to the excellent photothermal properties, low reflectance, and uniform heat dissipation pores. The water production efficiency of Tf-TA2/Ag sample is 1.41 kg·m−2·h−1 in artificial seawater and 0.76 kg·m−2·h−1 in oily sewage under simulated sun irradiation. Furthermore, the hydrophilic and oleophobic properties of Tf-TA2/Ag are critical to extracting water from oil/water mixture in diverse water environments. Ultimately, this four-birds-with-one-stone approach provides a new perspective for the improvement of solar seawater desalination performance.

Research Article Issue
Cobalt disulfide/carbon nanofibers with mesoporous heterostructure and excellent hydrophilicity for high energy density asymmetric supercapacitor
Nano Research 2023, 16 (7): 10401-10411
Published: 02 March 2023

Herein, a unique mesoporous heterostructure (average pore size: 15 nm) cobalt disulfide/carbon nanofibers (CoS2/PCNFs) composite with excellent hydrophilicity (contact angle: 23.5°) is prepared using polyethylene glycol (PEG) as a pore-forming agent. The CoS2/PCNF electrode exhibits excellent cycle stability (95.2% of initial specific capacitance at 10 A∙g−1 after 8000 cycles), good rate performance (46.5% at 10 A∙g−1), and high specific capacity (86.1 mAh∙g−1 at 1 A∙g−1, about 688.8 F∙g−1 at 1 A∙g−1). Density functional theory (DFT) simulation elucidates that CoS2 tends to transfer substantial charges to CNF. As the center of positive charge, CoS2 is more likely to capture negative ions in the electrolyte, thus accelerating the ion diffusion process. The excellent properties of the electrode material can not only accelerate the electrochemical reaction kinetics, but also provide abundant redox-active sites and a high Faradaic capacity for the entire electrode due to the synergistic contributions of CoS2 nanoparticles, mesoporous heterostructure of PCNF, and admirable hydrophilicity of the composite material. A CoS2/PCNF-0.25//AC (AC: activated carbon) asymmetric supercapacitor is assembled using CoS2/PCNF-0.25 as the positive electrode and AC as the negative electrode, which possesses a high energy density (35.5 Wh∙kg−1 at a power density of 824 W∙kg−1) and superior cycling stability (maintaining over 98% of initial capacitance after 2000 cycles). In addition, the unique CoS2/PCNF electrode is expected to be widely used in other electrochemical energy storage devices, such as lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, etc.

Research Article Issue
Hierarchical polypyrrole@cobalt sulfide-based flexible on-chip microsupercapacitors with ultrahigh energy density for self-charging system
Nano Research 2023, 16 (1): 555-563
Published: 10 November 2022

Herein, we prepare the unique hierarchical polypyrrole@cobalt sulfide (PPy-hs@CoS) hollow sphere-based nanofilms as interdigitated electrodes for flexible on-chip micro-supercapacitors (MSC). Benefiting from the excellent flexibility and high electrical conductivity of PPy-hs combined with the great electrochemical activity of CoS, such PPy-hs@CoS composite material can not only inhibit the volume expansion of PPy but also promote the diffusion of the electrolyte ions. The PPy-hs@CoS film-based electrode delivers a greatly improved specific capacitance and small resistance. Density functional theory calculations infer that OH prefers to bind to PPy on CoS@PPy and confirms the synergistic effect of each component for enhanced reaction kinetics. A quasi-solid-state on-chip flexible asymmetric MSC based on PPy-hs@CoS and activated carbon (AC) microelectrodes exhibits large areal-specific capacitance (131.9 mF/cm2 at 0.3 mA/cm2), ultrahigh energy density (0.041 mWh/cm2@0.224 mW/cm2 and 25.6 mWh/cm3@140.6 mW/cm3), and long cycle lifespan. We demonstrate the possibility to scale up the PPy-hs@CoS nanofilm microelectrode by arranging two of our asymmetric MSC in series and parallel connections, which respectively increase the output voltage and current. A self-charging system by connecting our asymmetric MSCs with a piece of commercial solar cells is developed as a potential possible mode for future highly durable and high-voltage integrated electronics.

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