Preparation of strong, tough and conductive soy protein isolate/poly(vinyl alcohol)-based hydrogel via the synergy of biomineralization and salting out.

Conductive hydrogels have shown a great potential in the field of flexible electronic devices. However, conductive hydrogels prepare by traditional methods are difficult to combine high strength and toughness, which limits their application in various fields. In this study, a strategy for preparing conductive hydrogels with high strength and toughness by using the synergistic effect of biomineralization and salting-out was pioneered. In simple terms, by immersing the CaCl2 doped soy protein isolate/poly(vinyl alcohol)/dimethyl sulfoxide (SPI/PVA/DMSO) hydrogel in Na2CO3 and Na3Cit complex solution, the biomineralization aroused by Ca2+ and CO32-, and the salting-out effect of both NaCl and Na3Cit would enhance the mechanical properties of SPI/PVA/DMSO hydrogel. Meanwhile, the ionic conductivity of the hydrogel would also increase due the introduction of cation and anion. The mechanical and electrical properties of SPI/PVA/DMSO/CaCO3/Na3Cit hydrogels were significantly enhanced by the synergistic effect of biomineralization and salting-out. The optimum tensile strength, toughness, Young's modulus and ionic conductivity of the hydrogel were 1.4 ± 0.08 MPa, 0.51 ± 0.04 MPa and 1.46 ± 0.01 S/m, respectively. The SPI/PVA/DMSO/CaCO3/Na3Cit hydrogel was assembled into a strain sensor. The strain sensor had good sensitivity (GF = 3.18, strain in 20 %-500 %) and could be used to accurately detect various human movements.

Ultra-Low Loading of Ultra-Small Fe3 O4 Nanoparticles on Nonmodified CNTs to Improve Green EMI Shielding Capability of Rubber Composites.

From a material design perspective, the incorporation of Fe3 O4 @carbon nanotube (Fe3 O4 @CNT) hybrids is an effective approach for reconciling the contradictions of high shielding and low reflection coefficients, enabling the fabrication of green shielding materials and reducing the secondary electromagnetic wave pollution. However, the installation of Fe3 O4 nanoparticles on nonmodified and nondestructive CNT walls remains a formidable challenge. Herein, a novel strategy for fabricating the above-mentioned Fe3 O4 @CNTs and subsequently assembling segregated Fe3 O4 @CNT networks in natural rubber (NR) matrices is proposed. The advanced and unique structure, magnetism, and lossless conductivity endow the as-obtained Fe3 O4 @CNT/NR with a shielding effectiveness (SE) of 63.8 dB and a low reflection coefficient of 0.24, which indicates a prominent green-shielding capability that surpasses those of previously reported green-shielding materials. Moreover, the specific SE reaches 531 dB cm-1 , exceeding that of those of previously reported carbon/polymer composites. Meanwhile, the outstanding conductivity enables the composite to reach a saturation temperature of ≈95 °C at a driving voltage of 1.5 V with long-term stability. Therefore, the as-fabricated Fe3 O4 @CNT/rubber composites represent an important development in green-shielding materials that are applied in cold environment.

Preparation of Tough and Adhesive PVA/P(AM-AMPS)/Glycerol/Laponite/Na2SO4 Organohydrogels for All-Solid-State Supercapacitors and Self-Powered Wearable Strain Sensors.

Hydrogel electrolytes are ideal for flexible wearable electronic devices because of their high ionic conductivity, flexibility, and biocompatibility. However, some problems, such as poor mechanical properties, low conductivity, and lack of adhesivity, are encountered in the process of hydrogel preparation and application, which restrict the further development of hydrogel electrolytes. In this study, PVA was used as the first network, and P(AM-co-AMPS) as the second network to prepare a double-network hydrogel electrolyte. Laponite and Na2SO4 were introduced into the hydrogel during hydrogel formation as the nanofiller and salt with the salting-out effect to enhance its mechanical properties. The hydrogel electrolyte with high toughness (1663 kJ·m-3), adhesivity (77 kPa), and ionic conductivity (1.7 S·m-1) was obtained. In addition, the hydrogel electrolyte also has excellent antifatigue performance. In the 10 consecutive tensile cycles, the tensile strength does not decay. Due to the high adhesivity of the hydrogel electrolyte, a symmetrical all-solid-state supercapacitor was assembled with a tight interface between the hydrogel electrolyte and the AC/CNT composite electrode. The supercapacitor has a high specific capacitance of 186.1 mF·cm-2 at the current density of 1 mA·cm-2. In addition, the capacitor has good flexibility and can withstand bending at various angles. The hydrogel electrolyte also has excellent strain sensing performance, with an ultrafast tensile response time (0.17 s) and high sensitivity factor (GF = 10.01). Finally, the self-powered sensor system composed of a supercapacitor as the power supply device and hydrogel electrolyte as the sensing part was obtained and applied to human motion monitoring, which provides a potential application in the integrated flexible electronic system.

Freezing-resistant poly(N-isopropylacrylamide)-based hydrogel for thermochromic smart window with solar and thermal radiation regulation.

Adaptive regulation of solar and thermal radiation by windows in diverse (hot and cold) climates is essential to reduce building energy consumption. However, conventional hydrogel-based thermochromic smart windows lack thermal radiation regulation, and have difficulty to combine high solar regulation with excellent freezing resistance. It is challenging to integrate the above performance into one hydrogel-based thermochromic window. Here, we firstly prepared poly(N-isopropylacrylamide-co-N, N-dimethylacrylamide)/ethylene glycol (PNDE) hydrogels with tunable and excellent freezing resistance (below -100 °C) by adding the anti-freezing agent ethylene glycol, and assembled PNDE hydrogels, polyvinylidene fluoride and polymethyl methacrylate-silver nanowires panels into a freezing-resistant smart window with solar and thermal radiation regulation (STR). PNDE hydrogels had an excellent thermochromic performance with luminous transmittance (Tlum) of 89.3 %, solar regulation performance (ΔTsol) of 80.7 % and tunable phase change temperature (τc, 22-44 °C). The assembled STR window showed high Tlum of 68.2 %, high ΔTsol of 62.6 %, suitable τc of ∼30 °C and freezing resistance to low temperature of -27 °C. Moreover, the different thermal emissivity (0.94 and 0.68) of the two sides of the STR window gave it the ability of radiative cooling in hot climates and warm-keeping in cold climates. Compared to the conventional thermochromic windows, the STR window promotes heat dissipation in hot conditions while reduces heat loss in cold conditions and is applicable to diverse climates, which is a promising energy-saving device for reducing building energy consumption.

A high-strength, environmentally stable, and recyclable starch/PVA organohydrogel electrolyte for flexible all-solid-state supercapacitor.

Hydrogel electrolytes have shown great promise in the field of flexible energy storage. However, the conventional hydrogel electrolytes have poor mechanical properties and are not recyclable. In addition, conventional hydrogel electrolytes cannot adapt to low and high temperature operating environments. In this study, starch/PVA/dimethyl sulfoxide/CaCl2 (SPDC) organohydrogel was prepared by the freezing-thawing method. Dimethyl sulfoxide (DMSO) and CaCl2 was introduced to enhance the mechanical properties and widen the working temperature range of the starch/PVA hydrogel. The SPDC organohydrogel had high strength, toughness and good recyclability. The SPDC organohydrogel and the recycled SPDC organohydrogel was used as the electrolyte to assemble the flexible supercapacitor with activated carbon as the electrode. The supercapacitor prepared by SPDC organohydrogel electrolyte exhibited high areal capacitance of 156.50 mF/cm2 at a current density of 1 mA/cm2 and high capacitance retention rate of 82.23 % after 8000 cycles of charging and discharging. The supercapacitor prepared by the recycled organohydrogel electrolyte exhibited a high capacitance retention rate of 97.58 %. In addition, the supercapacitor could withstand different angular bending shapes and had wide temperature adaptability from -20 °C to 80 °C. The work provided a new version for the development of "green" hydrogel electrolyte for all-solid-state supercapacitor.

Printable Thermochromic Hydrogel-Based Smart Window for All-Weather Building Temperature Regulation in Diverse Climates.

Thermochromic smart windows are widely developed to modulate building energy exchange to save building energy consumption. However, most smart windows have fixed working temperatures, moderate energy-saving efficiency, and are not suitable for diverse (cold and hot) climates. Here smart windows with strong temperature modulation over a broad range of hydrogels with adjustable transition temperatures for all-weather building temperature regulation in different climates are reported. Thermochromic poly(N-isopropylacrylamide-co-N, N-dimethylacrylamide) hydrogels, with lower critical transition temperatures ranging from 32.5 to 43.5 °C, are developed for smart windows with solar modulation up to 88.84% and intrinsic transmittance up to 91.30% over full spectrum without energy input. Simulated indoor investigations are performed in different cities from 23 °N to 39 °N from winter to summer. The results indicate that smart windows have a strong solar modulation in summer to reduce indoor temperature up to 7.3 °C and efficient heat conservation in winter to save energy up to 4.30 J m-3 , in comparison to glass windows. Smart windows with grid patterns and Chinese kirigami are fabricated by using 3D printing of the hydrogels to achieve both solar modulation and light incidence. The strategy offers an innovative path for thermochromic smart windows for low carbon economy.

Thermo-Responsive Poly(N-isopropylacrylamide)/Hydroxypropylmethyl Cellulose Hydrogel with High Luminous Transmittance and Solar Modulation for Smart Windows.

Thermochromic smart windows are considered to be promising energy-saving devices for reducing energy consumption in buildings. The ideal materials for thermochromic smart windows should have high transmittance, high solar modulation, low phase-transition temperature, and excellent high-temperature thermal stability, which are difficult to achieve simultaneously. This work reports a simple one-step low-temperature polymerization method to prepare a thermo-responsive poly(N-isopropylacrylamide)/hydroxypropylmethyl cellulose (PNIPAM/HPMC) hydrogel achieving the above performances simultaneously. The low-temperature polymerization environment endowed the hydrogel with a high luminous transmittance (Tlum) of 90.82%. HPMC as a functional material effectively enhanced the mechanical properties and thermal stability of the hydrogel. Meanwhile, the PNIPAM/HPMC hydrogel showed a low phase-transition temperature (∼32 °C) and high solar modulation (ΔTsol = 81.52%), which proved that it is an ideal material for thermochromic smart windows. Moreover, a PNIPAM/HPMC smart window exhibited high light transmittance (T380-760 = 86.27%), excellent light modulation (ΔT365 = 74.27%, ΔT380-760 = 86.17%, and ΔT940 = 63.93%), good indoor temperature regulation ability and stability, which indicated that it was an attractive candidate for application in reducing energy consumption in buildings. This work also provides an option and direction for modifying PNIPAM-based thermochromic smart windows.

Highly tough and ionic conductive starch/poly(vinyl alcohol) hydrogels based on a universal soaking strategy.

High-performance hydrogels with favorable mechanical strength, high modulus, sufficient ionic conductivity and freezing resistance have far-ranging applications in flexible electronic equipment. Nevertheless, it is challenging to combine admirable mechanical properties and high ionic conductivity into one hydrogel. Herein, a facile strategy was developed for the preparation of the hydrogel with excellent strength (1.45 MPa), super Young's modulus (8.85 MPa) and high conductivity (1.47 S/m) using starch and poly(vinyl alcohol) (PVA) as raw materials. The starch/PVA/Gly/Na3Cit (SPGN) gel was firstly cross-linked by crystalline regions of PVA upon freezing-thawing cycles. It was further immersed in the saturated Na3Cit solution to enhance the interaction between the substrates through the salting-out effect. The effect of soaking time on the crystallinity, intermolecular interactions, mechanical and electrical properties of SPGN gel was demonstrated by X-ray diffraction, Fourier transform infrared spectroscopy, tensile and impedance testing measurements. The introduction of glycerol and Na3Cit also endowed SPGN gels with favorable anti-freezing properties. The SPGN gel could maintain high mechanical flexibility and ionic conductivity at -15 °C.

Stimuli-Responsive Nanoparticles for Controlled Drug Delivery in Synergistic Cancer Immunotherapy.

Cancer immunotherapy has achieved promising clinical progress over the recent years for its potential to treat metastatic tumors and inhibit their recurrences effectively. However, low patient response rates and dose-limiting toxicity remain as major dilemmas for immunotherapy. Stimuli-responsive nanoparticles (srNPs) combined with immunotherapy offer the possibility to amplify anti-tumor immune responses, where the weak acidity, high concentration of glutathione, overexpressions of enzymes, and reactive oxygen species, and external stimuli in tumors act as triggers for controlled drug release. This review highlights the design of srNPs based on tumor microenvironment and/or external stimuli to combine with different anti-tumor drugs, especially the immunoregulatory agents, which eventually realize synergistic immunotherapy of malignant primary or metastatic tumors and acquire a long-term immune memory to prevent tumor recurrence. The authors hope that this review can provide theoretical guidance for the construction and clinical transformation of smart srNPs for controlled drug delivery in synergistic cancer immunotherapy.

Tough chitosan/poly(acrylamide-acrylic acid)/cellulose nanofibrils/ethylene glycol nanocomposite organohydrogel with tolerance to hot and cold environments.

Simultaneously achieving good mechanical properties and high tolerance to hot and cold environments in hydrogel materials remains a challenge. In this work, ethylene glycol (EG) and cellulose nanofibrils (CNFs) were introduced into chitosan/poly(acrylamide-acrylic acid) double-network hydrogels to improve their toughness and tolerance to hot and cold environments. The effect of EG and CNFs on the properties of the hydrogels was studied respectively. EG increases the tolerance of the hydrogel to hot and cold environments. However, EG had a negative effect on the mechanical properties of hydrogels. In addition, CNFs substantially enhanced the strength and toughness of the chitosan/poly(acrylamide-acrylic acid)/EG organohydrogels. Finally, with the cooperative action of EG and CNFs, high-strength and tough organohydrogels (tensile strength = 0.71 MPa, elongation at break = 787.2%) with a high tolerance to hot and cold environments (-23 °C to 60 °C) were obtained. Further, EG enabled the organohydrogel to revert to its original state after drying at 60 °C. This paper provides a new route to prepare high-strength and tough organohydrogels with a high tolerance to hot and cold environments.

Superhydrophobic and Flexible Silver Nanowire-Coated Cellulose Filter Papers with Sputter-Deposited Nickel Nanoparticles for Ultrahigh Electromagnetic Interference Shielding.

Superhydrophobic, flexible, and ultrahigh-performance electromagnetic interference (EMI) shielding papers are of paramount importance to safety and long-term service under external mechanical deformations or other harsh service environments because they fulfill the growing demand for multipurpose materials. Herein, we fabricated multifunctional papers by incorporating sputter-deposited nickel nanoparticles (NiNPs) and a fluorine-containing coating onto cellulose filter papers coated with silver nanowires (AgNWs). AgNW networks with sputter-deposited NiNPs provide outstanding magnetic properties, electrical conductivity, and EMI shielding performance. At an AgNW content of 0.109 vol % and a NiNP content of 0.013 mg/cm2, the resultant papers exhibit a superior EMI shielding effectiveness (SE) of 88.4 dB. Additionally, the fluorine-containing coating endows the resultant papers with a high contact angle of 149.7°. Remarkably, the obtained papers still maintain a high EMI SE even after 1500 bending cycles or immersion in water, salt, or strong alkaline solutions for 2 h, indicating their outstanding mechanical robustness and chemical durability. This work opens a new window for designing and implementing ultrahigh-performance EMI shielding materials.

Multifunctional Poly(vinyl alcohol) Nanocomposite Organohydrogel for Flexible Strain and Temperature Sensor.

Hydrogels are important for stretchable and wearable multifunctional sensors, but their application is limited by their low mechanical strength and poor long-term stability. Herein, a conductive organohydrogel with a 3D honeycomb structure was prepared by integrating carbon nanotubes (CNTs) and carbon black (CB) into a poly(vinyl alcohol)/glycerol (PVA/Gly) organohydrogel. Such a nanocomposite organohydrogel is built on a physical cross-linking network formed by the hydrogen bonds among PVA, glycerol, and water. CNTs and CB had an add-in synergistic impact on the mechanical and electrical performances of the PVA/Gly organohydrogel because of the distinct aspect ratios and geometric shapes. The prepared organohydrogel integrated with a tensile strength of 4.8 MPa, a toughness of 15.93 MJ m-3, and flexibility with an elongation at break up to 640%. The organohydrogels also showed good antifreezing feature, long-term moisture retention, self-healing, and thermoplasticity. Sensors designed from these organohydrogels displayed high stretching sensitivity to tensile strain and temperature, with a gauge factor of 2.1 within a relatively broad strain range (up to ∼600% strain), a temperature coefficient of resistance of -0.935%·°C-1, and long-term durability. The sensors could detect full-range human physiological signals and respond to the change in temperature, which are highly desired for multifunctional wearable electronic devices.

A facile preparation method for anti-freezing, tough, transparent, conductive and thermoplastic poly(vinyl alcohol)/sodium alginate/glycerol organohydrogel electrolyte.

Facile preparation of organohydrogel electrolyte integrated with good anti-freezing property, toughness, transparency, conductivity and thermoplasticity is important and still remains challenging. Novel conductive and tough poly(vinyl alcohol)/sodium alginate/glycerol (PVA/SA/Gly) composite organohydrogel electrolytes were obtained by a simple method in this paper. PVA and SA was firstly dissolved in a mixed solution of distilled water and glycerol and the PVA/SA/Gly organohydrogel was obtained by the freezing-thawing process, then PVA/SA/Gly organohydrogel was immersed into the saturated NaCl aqueous solution. During the soaking process NaCl would enter into the PVA/SA/Gly organohydrogel to increase the gel strength and conductivity. The PVA/SA/Gly organohydrogel electrolytes performed the high toughness with the tensile strength and elongation at break of 1.43 MPa and 558%, respectively. Moreover, the PVA/SA/Gly organohydrogel electrolytes behaved high transparency, anti-freezing property, conductivity and thermoplasticity due to the incorporation of glycerol. This paper provides a new preparation method for the high-performance organohydrogel electrolyte.

Functionalizing Double-Network Hydrogels for Applications in Remote Actuation and in Low-Temperature Strain Sensing.

Multifunctional hydrogels have important applications in various fields such as artificial muscles, wearable devices, soft robotics, and tissue engineering, especially for those with favorable mechanical properties, good low-temperature resistance, and stimuli-responsive capabilities. In the current study, a type of polyacrylamide/sodium alginate/carbon nanotube (PAAm/SA/CNT) double-network (DN) hydrogel was fabricated, which exhibited a high tensile strength of 271.68 ± 6.04 kPa, a favorable conductivity of 1.38 ± 0.17 S·m-1, and a good self-healing ability under heating conditions. In addition, the composite hydrogel exhibited controllable photomechanical deformations under near-infrared irradiation, such as bending, swelling, swimming, and object grasping. To further broaden the applications of the hydrogel in low-temperature environments, calcium chloride (CaCl2) was introduced into such a PAAm/SA/CNT DN hydrogel as an additive. Interestingly, the tensile/compressive strengths as well as elasticity were well-maintained at a temperature as low as -20 °C. In addition, the PAAm/SA/CNT/CaCl2 hydrogel presented excellent conductivity, recoverability, and strain-sensing capability under such extreme conditions. Overall, the investigations conducted in this paper have provided potentially new methods and inspirations for the generation of multifunctional PAAm/SA/CNT/CaCl2 hybrid DN hydrogels toward extended applications.

Facile preparation and characterization of super tough chitosan/poly(vinyl alcohol) hydrogel with low temperature resistance and anti-swelling property.

Facile preparation of super tough hydrogels with low temperature tolerance and anti-swelling property is still a challenging task for researchers. Meanwhile, the vast majority of tough hydrogels were obtained though chemical crosslinking and complicated synthesis or processing method accompanying a large number of harmful chemical reagents. Herein, the super tough chitosan/poly(vinyl alcohol) (CS/PVA) hydrogels (the maximum compressive strength of 18.97 MPa at a strain of 80% and the maximum tensile strength of 4.02 MPa at a strain of 406.4%) were successfully prepared via a simple post-treatment method. CS/PVA hydrogels were firstly prepared by freezing-thawing process and then soaking in saturated sodium chloride aqueous solution. The resultant hydrogels possess excellent swelling resistance and low temperature tolerance. This work shows that the post-treatment of immersing in saline solution is a feasible way to prepare super tough hydrogels with low temperature tolerance and anti-swelling property. This also would enlarge the application areas of CS.

Facile synthesis of MnO2 nanorods grown on porous carbon for supercapacitor with enhanced electrochemical performance.

Novel MnO2-doped holey carbon materials were obtained by an efficient and facile synthetic method using chitosan, potassium hydroxide and potassium permanganate as the raw materials. The carbon framework with high specific surface area was derived from chitosan by carbonization and activation approach, afterwards, MnO2 nanorods were grown on the surface of porous carbon by one-step agitation method and the MnO2-doped holey carbon material was obtained. The scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, X-ray diffraction, N2 adsorption-desorption measurements, Raman spectroscopy and X-ray photoelectron spectroscopy were employed to analyze the physicochemical characteristics of the MnO2-doped holey carbon materials. The electrochemical performance of these materials displayed well through relative tests including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy measurements in 6.0 M KOH solution. Especially, this as-obtained electrode material with the optimum ratio presented a high gravimetric capacitance (460F g-1 at 0.2 A g-1) and exceptional capacitance reservation (91.67% at 10 A g-1 over 10,000 cycles) in the three-electrode system with 6.0 M KOH solution as the electrolyte.

Preparation and characterization of novel magnetic Fe3O4/chitosan/Al(OH)3 beads and its adsorption for fluoride.

A novel magnetic bioadsorbent beads composed of Fe3O4, chitosan, and Al(OH)3 (Fe3O4/CS/Al(OH)3) was synthesized by a modified solvothermal and in-situ reaction. The composite adsorbent was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and vibrating sample magnetometer, respectively. Adsorption toward F- onto Fe3O4/CS/Al(OH)3 was investigated as a function of Fe3O4 concentration, initial solution pH, adsorbent dosage, initial fluorion concentration, co-existing ions in water and initial temperature. The addition of Fe3O4 could enhance the adsorption properties of CS/Al(OH)3. The saturated adsorption capacity of magnetic Fe3O4/CS/Al(OH)3 calculated from the Langmuir isotherm model was 76.63mg/g at 298K. The adsorption isotherm of F- followed Langmuir isotherm model and the adsorption kinetics fitted better to the pseudo-second order kinetic model. The influence of temperature confirmed that the adsorption was spontaneous and endothermic. The magnetic Fe3O4/CS/Al(OH)3 beads could be easily separated from water under a low magnetic field.

Preparation and characterization of poly(vinyl alcohol)/sodium alginate hydrogel with high toughness and electric conductivity.

Development of bio-based hydrogels with good mechanical properties and high electrical conductivity is of great importance for their excellent biocompatibility and biodegradability. Novel electrically conducive and tough poly(vinyl alcohol)/sodium alginate (PVA/SA) composite hydrogel was obtained by a simple method in this paper. PVA and SA were firstly dissolved in distilled water to form the composite solution and the pure PVA/SA hydrogel was obtained through the freezing/thawing process. The pure PVA/SA hydrogels were subsequently immersed into the saturated NaCl aqueous solution to increase the gel strength and conductivity. The effect of the immersing time on the thermal and mechanical properties of PVA/SA hydrogel was studied. The swelling properties and the antiseptic properties of the obtained PVA/SA hydrogel were also studied. This paper provided a novel way for the preparation of tough hydrogel electrolyte.

Preparation and characterization of quaternized poly(vinyl alcohol)/chitosan/MoS2 composite anion exchange membranes with high selectivity.

In this study, a series of novel quaternized poly(vinyl alcohol)/chitosan/molybdenum disulfide (QPVA/CS/MoS2) anion exchange membranes (AEMs) were prepared for direct methanol alkaline fuel cell (DMAFC). The composite membrane was synthesized by adding different amounts of MoS2 nanosheets (0, 0.1, 0.2, 0.5 and 1wt%) into QPVA/CS mixture solution and using the solution casting method. The crystallinity, thermal and mechanical properties, ion conductivity and resistance to methanol of the QPVA/CS/MoS2 membranes were characterized by X-ray diffraction, thermogravimetric analysis, tensile testing, ion exchange capacity, and methanol permeability measurements, respectively. The MoS2 was homogeneously dispersed in the membranes. The mechanical strength of the composite membranes was enhanced with the addition of MoS2. With the addition of 1.0wt% MoS2, the QPVA/CS/MoS2 composite membrane has the lowest methanol permeability of 0.210×10-7cm2·s-1. This study confirmed that the novel QPVA/CS/MoS2 membrane would be a potential candidate for the application in DMAFCs.

Hierarchical Porous Co9S8/Nitrogen-Doped Carbon@MoS2 Polyhedrons as pH Universal Electrocatalysts for Highly Efficient Hydrogen Evolution Reaction.

The development of highly active and stable earth-abundant electrocatalysts to reduce or eliminate the reliance on noble-metal based ones for hydrogen evolution reaction (HER) over a broad pH range remains a great challenge. Herein, hierarchical porous Co9S8/N-doped carbon@MoS2 (Co9S8/NC@MoS2) polyhedrons have been synthesized by a facile hydrothermal approach using highly conductive Co/NC polyhedrons composed of cobalt nanoparticles embedded in N-doped carbon matrices as both the structural support and cobalt source. The Co/NC polyhedrons were prepared by direct carbonization of Co-based zeolitic imidazolate framework (ZIF-67) in Ar atmosphere. Benefiting from the prominent synergistic effect of N-doped carbon enhancing the conductivity of the hybrid, MoS2 and Co9S8 providing abundant catalytically active sites as well as the well-defined polyhedral structure promoting mechanical stability, the as-synthesized Co9S8/NC@MoS2 shows excellent HER activity and good stability over a broad pH range, with onset overpotentials of 4, 38, and 45 mV, Tafel slopes of 60.3, 68.8, and 126.1 mV dec-1, and overpotentials of 67, 117, and 261 mV at 10 mA cm-2 in 1.0 M KOH, 0.5 M H2SO4, and 1.0 M phosphate buffer solution (PBS), respectively. This work provides a general and promising approach for the design and synthesis of inexpensive and efficient pH-universal HER electrocatalysts.