Dual-function Material Research Articles

Modeling of temperature swing adsorption-oxidation of volatile organic compounds

In this work, we simulated a single-bed 4-step temperature swing adsorption-oxidation (TSAO) process for capture and in situ oxidation of benzene, as a model VOC, over Ni/ZrO2-SiO2, as a dual-function material (DFM). The TSAO cycles consisted of adsorption, preheating, desorption/oxidation, and cooling steps. The model sensitive parameters were estimated via parameter estimation and validated against experimental data. Extensive parametric analysis was carried out to investigate the effects of key process variables on the TSAO performance. Model results revealed relatively good prediction of the process. Under the conditions investigated, adsorption, oxidation and total removal efficiencies were estimated to be 76, 84 and 66%, respectively. It was also established that the proposed 4-step cyclic TSAO could be reduced to a 3-step TSAO process consisting of adsorption, heating/desorption/oxidation, and cooling steps without any loss in performance. Finally, it was demonstrated that indirect convective cooling is far superior to direct feed cooling.

Dual function materials (Ru+Na2O/Al2O3) for direct air capture of CO2 and in situ catalytic methanation: The impact of realistic ambient conditions

A dual function material (DFM) comprised of 1% Ru, 10% Na2O/γ − Al2O3 was studied for combined direct air capture (DAC) of CO2 and catalytic methanation in a temperature swing operation. In the newly proposed operation, the DFM captures CO2 (400 ppm) from air at ambient conditions. The material is then heated in H2 to a temperature sufficient for catalytic conversion of the captured CO2 to renewable natural gas. In this study, we demonstrate high CO2 adsorption capacity and rates at ambient conditions (25 °C); the adsorbed CO2 is then successfully catalytically methanated upon heating in H2. Adsorption was also carried out in humid conditions, more closely simulating ambient air. Adsorption and methane production were greatly improved with stable initial performance. The rate of adsorption is shown to be flowrate-dependent, which is critical for future reactor design.

Remediating oxytetracycline-contaminated aquaculture water using nano calcium peroxide (nCaO2) produced from flue gas desulfurization (FGD) gypsum

Antibiotic-contaminated water, particularly oxytetracycline (OTC), which is widely used in aquaculture, can threaten human health through the ingestion of edible aquatic organisms. The objective of this study was to develop novel and cost-effective calcium peroxide nanoparticles (nCaO 2 ), synthesized using flue gas desulfurization (FGD) gypsum for improving water quality and OTC removal. The nCaO 2 -FGD was synthesized using a 1:7 (FGD:H 2 O 2 ) mixture. The results showed that nCaO 2 -FGD had spherical particles with diameters of 20–60 nm. The dissolved oxygen production in water by nCaO 2 -FGD significantly increased, with an oxygen release rate of 0.0079 min −1 . The nCaO 2 -FGD achieved OTC removal of 83.92% within 48 h. Radical trapping experiments revealed that hydroxyl radical, superoxide ion, and singlet oxygen play important roles in OTC degradation. The mineralization of the OTC investigated by total organic carbon (TOC) was 71 ± 4%. The nCaO 2 -FGD dosage, initial OTC concentration, carbonate ion, and humic acid (HA) significantly affected OTC removal, while the initial pH and chloride ion did not at the 95% confidence level. Using response surface methodology, we found that the optimum conditions for treating 10 mg/L of OTC were 53.25 mg/L HA, 558.72 mg/L CO 3 2 − and 2,320.75 mg/L CaO 2 -FGD. The nCaO 2 -FGD encapsulated in alginate aided in maintaining the pH of water (pH 6.5–7). The nCaO 2 -FGD was then used to treat real aquaculture water. After 48 h, 10 mg/L of OTC was degraded by 75.83 ± 2.1%. The zooplankton communities in the aquaculture water did not significantly differ before and after treatment. Therefore, our results indicate that nCaO 2 -FGD is safe for implementation • FGD gypsum, a solid waste byproduct of coal-based power generation, was economically utilized. • As a novel dual-function material, nCaO 2 -FGD acts as an oxygen-release and effective oxidizing material. • O 2 was released mainly from nCaO 2 -FGD dissolution. • Active radicals generated in the nCaO 2 -FGD/water system play important roles in degrading OTC.

Electrospinning technology to prepare in-situ Cr2O3 modified carbon nanofibers as dual-function electrode material for vanadium redox battery

Electrospinning is a special fiber manufacturing process, which has the advantages of simple equipment, low cost, and controllable process conditions. Cr2O3 is grown in situ on carbon nanofibers by electrospinning technology. The effects of different contents of Cr2O3 on the morphology and physicochemical properties of carbon nanofibers are systematically studied. The in-situ Cr2O3 nanoparticles were distributed evenly on the carbon nanofibers, which increase the defect degree of the carbon nanofibers. The carbon fiber electrode modified by Cr2O3 has good electrochemical reversibility and activity for vanadium ion redox reaction. At 150 mA·cm−2, compared with pristine cell, the discharge capacity and energy efficiency of modified battery are increased by 77.2% and 6%, respectively. The energy storage performance of modified battery has been significantly improved. The synergistic effect of carbon nanofibers and second phase catalyst Cr2O3 with high catalytic performance can effectively enhance the performance of VRFB.

An Imidazole Thione-Modified Polyhedral Oligomeric Silsesquioxane for Selective Detection and Adsorptive Recovery of Au(III) from Aqueous Solutions.

Developing a material toward simultaneous detection and recovery of gold ions (Au(III)) is highly desirable for the economy and the environment. Herein, we report a highly efficient dual-function material for simultaneous Au(III) detection and recovery by simply introducing abundant imidazole thione and thioether groups in one system. This material, that is, an imidazole thione-modified polyhedral oligomeric silsesquioxane (POSS-2), was prepared by a mild reaction of an imidazolium-containing POSS and sulfur at ambient temperature. The POSS-2 suspension in water can rapidly and selectively detect Au(III) with a very low limit of detection of 1.2 ppb by fluorescence quenching or a visualized color change from white to dark orange. POSS-2 can also selectively and efficiently capture Au(III) with a maximum adsorption uptake of 1486.5 mg/g. The adsorption process well fits with the pseudo-second-order kinetic and Langmuir models. The intriguing dual-function performance is better than most of the previous Au(III) probes or adsorbents. The mechanism study reveals that the detection and adsorption behavior are mainly caused by the redox reaction and coordination between imidazole thione and thioether groups and Au(III). Furthermore, POSS-2 was successfully utilized to extract gold without interference from a discard CPU. These results indicate the potential application of the present dual-function material for Au(III) detection and recovery from aqueous solutions. More dual-functional materials could be designed and prepared by this simple strategy.

BiOBr/PBCD-B-D dual-function catalyst with oxygen vacancies for Acid Orange 7 removal: Evaluation of adsorption-photocatalysis performance and synergy mechanism

The fabrication of a dual-function material is an effective strategy to promote the degradation of pollutants through the synergy of adsorption and photocatalysis. Herein, we introduce an amphiphilic hyper-crosslinked porous cyclodextrin polymer (PBCD-B-D) into bismuth oxide bromide (BiOBr) via a one-pot solvothermal method to construct three-dimensional (3D) spherical flower-shaped BiOBr/PBCD-B-D (BOP) composites for removing the organic dye Acid Orange 7 (AO7). The prepared BiOBr composite loaded with 24% PBCD-B-D (BOP-24) displayed an optimal adsorption–photocatalytic effect. Under different concentration gradients, the pseudo first-order reaction rate constant of BOP-24 was 2–5 times that of BiOBr after visible-light irradiation. The unique cavity structure of PBCD-B-D resulted in a strong inclusion ability, which could concentrate organic pollutants and shorten the mass transfer distance. The introduction of PBCD-B-D to BiOBr led to an increase in the specific surface area and pore volume, which not only provided a large number of adsorption sites and active centers but also produced oxygen vacancies to improve charge separation. In addition, a possible degradation pathway was proposed for AO7 based on 3D excitation-emission matrix fluorescence spectra and analysis by liquid chromatography-mass spectrometry. This work combines the advantages of both adsorption and photocatalytic technologies for environmental remediation, and opens an avenue for dual-function high-surface-area adsorbent/photocatalysts via a one-pot in situ method.

Ag and peptide co-decorate polyetheretherketone to enhance antibacterial property and osteogenic differentiation

Polyetheretherketone (PEEK) has been well concerned as a promising material for hard tissue repair because of its outstanding mechanical behavior and superior biocompatibility. However, its clinical application is limited by its biological inertness and the susceptibility to bacterial infection during implantation. To improve the original shortcomings, self-polymerized dopamine (PDA) was used to enrich silver ions on the PEEK surface. Moreover, a layer of carboxymethyl chitosan (CMC) film was formed on the PEEK surface by the spin-coating method, aiming to control the release of silver ions on the surface. At the same time, bone forming peptide (BFP) was modified onto the PEEK surface by 1-(3-dimethylaminopropyl)-3-ethylcarbonimide hydrochloride (EDC) / N-hydroxy succinimide (NHS). The characterization results showed that PEEK-Ag-CMC-BFP could be obtained successfully. The inhibition zone and bacterial kinetic curve showed a favorable inhibitory effect of the sliver-modified PEEK on gram-negative and gram-positive bacteria. In vitro experiments exhibited that PEEK-Ag-CMC-BFP had a better biological activity than that of PEEK, which could promote cell proliferation and osteogenic differentiation. It is expected that this dual-function material with antibacterial and bone-promoting properties has a vast potential applied in the field of hard tissue repair.

Ru-Ba synergistic effect in dual functioning materials for cyclic CO2 capture and methanation

Mechanistic aspects involved in cyclic CO2 capture and methanation were analyzed by comparing the catalytic behavior of a Ru-BaO/Al2O3 (intimate mixture) with that of a mechanical mixture of BaO/Al2O3 + Ru/Al2O3. Both combinations showed similar performance in the storage of CO2 and in the thermal stability of adsorbed species: CO2 is strongly adsorbed over the BaO component, and cannot be completely released even at high temperatures. The H2 reactivity of the stored species is strongly enhanced for the intimate mixture, showing increased CH4 formation at lower temperatures thus indicating the synergistic effect between the storage and hydrogenation functions. Dual Function Material (DFM) experiments performed in the presence of O2 and steam during the CO2 capture step showed a decrease in the amounts of adsorbed CO2 and a lower methanation rate. When NOx is also present during the capture step, the adsorption of CO2 is hindered by strongly adsorbed NOx. However, while Ru-BaO/Al2O3 can be fully regenerated by H2, BaO/Al2O3 + Ru/Al2O3 suffers from deactivation due to the buildup of adsorbed NOx. It should be understood that in power plant applications the DFM will be located downstream from SCR and therefore the level of NOx will be in the ppm level. Furthermore, it is completely desorbed as NH3 and N2 upon the addition of H2 and thus will not have a significant impact of overall performance for CO2 capture and conversion.

CO2-SR Cyclic Technology: CO2 Storage and in situ Regeneration with CH4 over a new dual function NiBa unsupported catalyst

A Ni-Ba unsupported catalyst has been developed to be used as a dual function material (DFM) for a new CO2 storage and in-situ regeneration (CO2-SR technology), consisting in a CO2 storage step followed by a CH4 regeneration phase, working in alternating, cyclic and isothermal regime. The heterometallic mixed-oxide catalyst -NiO.BaO- used in this technology was prepared by an ultrasonic assisted coprecipitation using 1:1 atomic ratio (Ni:Ba) and colloidal silica as an agent promoting surface area and improving mechanical properties. The solid obtained maintains the fcc-structure at higher temperatures, demonstrates high reducibility as a bulky catalyst and presents a connected and balanced strong basic sites and CH4 activation centres. It showed a CO2-storage net capacity of 0.232 mmolCO2 g−1 and a CO2 and CH4 removal rate of 13.97 % and 11.04 % respectively, with a remarkable selectivity to hydrogen as an enriched-synthesis gas (H2+CO) stream at 600 °C.

Vapor solid phase grown hierarchical CuxO NWs integrated MOFs-derived CoS2 electrode for high-performance asymmetric supercapacitors and the oxygen evolution reaction

Designing and exploring a simple, novel, and smart synthetic concept to fabricate highly efficient and dual-function electrode material at an optimum cost for green energy harvesters has been a long-standing challenge. Herein, for the first time, we investigated a simple and smart concept to fabricate dual-function vapor solid phase grown copper oxide nanowires (CuxO NWs) integrated metal-organic frameworks-derived (MOFs) hollow and porous cobalt sulfide (CuxO NWs@CoS2) hybrid nanostructures as an effective binder-free electrode for supercapacitors and the OER. When utilized as an electrode material for supercapacitors, the CuxO NWs@CoS2 hybrid electrode displayed an ultrahigh specific capacity of 331.6 mAh/g (volumetric capacity of 2.46 mAh/cm3) with an outstanding rate capability of 67% even at a high current density of 50 mA/cm2; moreover, the electrode possessed a long-term durability of 100.2% after 10,000 cycles. An all-solid-state asymmetric device (CuxO NWs NWs@CoS2//Fe2O3/rGO aerogels) delivered a specific energy density of 49.8 Wh/kg. In addition, the oxygen evolution activity of the CuxO NWs@CoS2 electrode was also investigated and the electrode demonstrated superior catalytic properties compared to other formulations. This investigation emphasizes a novel synthetic approach and its multifunctional applicability in energy storage and generation devices.

Bimetallic catalysts for CO2 capture and hydrogenation at simulated flue gas conditions

A study of a dual function material (DFM) for CO2 capture from O2-containing flue gas with catalytic conversion to fuel is presented. The DFM is composed of an alkaline adsorbent in concert with a methanation catalyst supported on γ-Al2O3. The process operates at 320 °C for both CO2 capture and fuel generation upon the addition of renewable H2. Ni alone will not methanate adsorbed CO2 after exposure to O2 in the flue gas during CO2 capture since it oxidizes and cannot be reduced to Ni metal under DFM conditions (320 °C). We report that small amounts of precious metal (≤1% Pt, Pd or Ru) enhance the reduction and activation of Ni-containing DFM towards methanation even after O2 exposure in a flue gas. While ruthenium is most effective, Pt and Pd all enhance reduction of oxidized Ni. In this study we attempt to replace some of the Ru in the DFM with less expensive Ni and demonstrate the advantages and disadvantages of this replacement. The main advantage of the presence of Ni is an increase in CO2 adsorption and increase in methane produced, however, at the expense of a lower methanation rate. Extended cyclic aging studies corroborate the stable performance of 1% Ru, 10% Ni, 6.1% “Na2O”/Al2O3.

Development of the adsorption capability of MCM-41 particles synthesized at room temperature using 8-hydroxyquinoline-5-sulfonic acid for removal of Co(II) and Cr(VI) in binary systems

A novel MCM-41 material containing 8-hyrdoxyquinoline-5-sulfonic acid (HQS/MCM-41) synthesized by in-situ coprecipitation of 8-HQS into MCM-41 was developed in this study. The performance of HQS/MCM-41 as a dual-function material for simultaneous adsorption of Co(II) cations and Cr(VI) anions was evaluated. The results showed that 8-HQS-free MCM-41 has the ability to adsorb Cr(VI) anions while failed in case of Co(II) cations. By using HQS/MCM-41, almost complete removals are achieved for both Co(II) and Cr(VI) in binary systems in pH ranges 3.5–8.5 and 3–4.3, respectively, which reflected the importance of the developing agent 8-HQS. Both Lagergren’s pseudo-first-order and Ho’s pseudo-second-order kinetic models succeeded to describe the kinetic data of Cr(VI) anions while those of Co(II) cations are better fitted by Lagergren’s model. Equilibrium isotherms of Co(II) and Cr(VI) ions are better described by Temkin and Freundlich isotherm models, respectively. Adsorption capacities of Co(II) and Cr(VI) using HQS/MCM-41 are compared with those reported in literature using other materials. The radiation and thermal stability of the synthesized material were further evaluated. Desorption of Co(II) and Cr(VI) loaded onto HQS/MCM-41 was tested using different inorganic and organic desorbing agents. Eventually, the adsorption mechanism of Co(II) and Cr(VI) ions onto HQS/MCM-41 was suggested.

WO3−x for rapid adsorption and full-spectrum-responsive photocatalytic activities

Dual-purpose method for efficient removal of harmful organic dyes has been successfully realized by W18O49 nanostructure via fast absorption and advanced full-spectrum-responsive photocatalytic degradation from UV to near infrared (NIR). The removal more than 99% of MB could be finished as short as 1–2 min. The strong electrostatic interaction between the negative charged W18O49 surface and the cationic MB species is major reason for such a fast adsorption response. In addition, W18O49 nanostructure also could behave as photocatalyst for further degradation of MB. Advantages of W18O49 nanostructure used in this purpose benefit from its high optical absorption covering ultraviolet, visible light and NIR, which has good mineralizing ability under each spectrum, thus taking full use of solar energy. What is noteworthy, the regeneration of W18O49 after the absorption of MB could be simply realized by photo-irradiation process. As a result, it will be promising to use this dual-function material for deeply removal of organic dyes in wastewater.

Superb removal capacity of hierarchically porous magnesium oxide for phosphate and methyl orange.

Here, we successfully developed a template-free way to fabricate hierarchically porous magnesium oxide (MgO) and carefully investigated the adsorption behavior for phosphate and methyl orange (MO). The average pore size and the percentage porosity decreased with the increase in the feeding ratio of Mg2+/NH3. Among the three samples, MgO-25 shows the highest surface area of 63m2g-1 determined by the mercury intrusion method, and MgO-50 exhibits the highest BET surface area of 121m2g-1. For all the MgO samples, the adsorption process follows the pseudo second-order and Langmuir isotherm for phosphate, while pseudo second-order and the Freundlich isotherm for MO. Among the investigated samples, MgO-25 shows the most maximum removal capacity of 478.5mgg-1 for phosphate and the highest removal capacity of 4483.9mgg-1 for MO. This study compromises a low-cost and convenient dual function material for excellent water remediation of multiple industries.

Efficient removal of methyl orange using Cu2O as a dual function catalyst

In this study, we synthesized Cu2O particles with rough surfaces by a facile solvothermal method as a dual-function material that can degrade contaminants not only under light irradiation but also in dark circumstance. Both the as-prepared Cu2O and commercial Cu2O exhibited excellent performance for the removal of methyl orange under visible light irradiation through a photocatalysis-based strategy. However, the former was found to show remarkable capability under dark circumstances by means of molecular oxygen activation, while the latter performed poor efficiently under the same condition. This significant difference of performances under dark circumstances was related to rich oxygen vacancies existed on the as-prepared Cu2O surfaces that are associated with the single-electron reduction of O2 to generate O2−, which play a dominant role in the generation of Cu+. In addition, Cu+ was identified to play key roles in the broken of azo bond. Then, the generated intermediates were mineralized by OH generated through molecular oxygen activation process. This study could not only deep the understanding of the MO removal mechanism by Cu2O but also show a novel direction of amphibious application for photocatalytic materials.

Heteropolyacids supported on macroporous materials POM@MOF-199@LZSM-5: Highly catalytic performance in oxidative desulfurization of fuel oil with oxygen

A highly active catalyst Keggin type POM-based inorganic-organic compound POM@MOF-199@LZSM-5(PMZ) has been prepared and applied in the catalytic oxidative desulfurization system. Structure and properties of catalyst were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and so on. The catalyst gave high desulfurization activity in the removal of DBT using O2 as the oxidant. Under the optimal conditions, the conversion rate reached 100% only in 120 min. The kinetic studies revealed that the oxidative desulfurization can present a pseudo first-order kinetic process and the apparent activation energy was 30.5 kJ/mol. The response surface method also used to optimize the process of oxidative desulfurization. There was little change for the oxidative desulfurization efficiency after 10 recycle times. This enhanced catalytic performance could be attributed to the more filled active species, POM, in the larger porous materials and the good protection measures of dual-function porous material supports.

Intercalated Chevrel Phase Mo6S8 as a Janus Material for Energy Generation and Storage

An approach to designing solar absorber materials based on an intercalation-induced metal-to-semiconductor transition has been proposed. Using a hybrid density functional calculation, Al-intercalated Chevrel phase Mo6S8 with end product Al4/3Mo6S8 is predicted to be a semiconductor with a 1.18 eV indirect band gap. Compared with GaAs and Si, Al4/3Mo6S8 shows significantly higher optical absorption over the solar spectrum as a result of the parallel bands across the band gap with direct transitions around 1.35 eV, nearly ideal for an absorber material in a solar cell. Chevrel phase Mo6S8 has recently been explored as a cathode material in rechargeable Al-ion batteries. Thus, Al4/3Mo6S8 is a potential dual-function (or Janus) material for both energy generation and storage. A possible device structure utilizing this unique property has been proposed.

A Ferroelectric Iron(II) Spin Crossover Material.

A dual-function material in which ferroelectricity and spin crossover coexist in the same temperature range has been obtained. Our synthetic strategy allows the construction of acentric crystal structures in a predictable way and is based on the high directionality of hydrogen bonds. The well-known iron(II) spin crossover complex [Fe(bpp)2 ]2+ (bpp=2,6-bis(pyrazol-3-yl)pyridine), a four-fold noncentrosymmetric H-bond donor, was combined with a disymmetric H-bond acceptor such as the isonicotinate (isonic) anion to afford [Fe(bpp)2 ](isonic)2 ⋅2 H2 O. This low-spin iron(II) compound crystallizes in the acentric nonpolar I4‾ space group and shows piezoelectricity and SHG properties. Upon dehydration, it undergoes a single-crystal to single-crystal structural rearrangement to a monoclinic polar Pc phase that is ferroelectric and exhibits spin crossover.

Investigation on CFRP as dual-functional material in chloride-contaminated solutions

This paper investigates the performance of carbon fibre reinforced polymer (CFRP) as a dual function material in combined impressed current cathodic protection and structural strengthening of reinforced concrete structures. Tests in solution showed that CFRP maintain stable electrical conductivity after 80 d accelerated anodic polarization. Results suggest that oxygen evolution occurring at low chloride ion concentration ([Cl−]) primarily damages the carbon fibre, while chlorine evolution occurring at high [Cl−] primarily damages the epoxy resin. The tensile strength of CFRP after anodic polarization decreases with increasing circulated charge, and, for a given circulated charge, it increases with increasing [Cl−].

The Role of Ruthenium in CO2 Capture and Catalytic Conversion to Fuel by Dual Function Materials (DFM)

Development of sustainable energy technologies and reduction of carbon dioxide in the atmosphere are the two effective strategies in dealing with current environmental issues. Herein we report a Dual Function Material (DFM) consisting of supported sodium carbonate in intimate contact with dispersed Ru as a promising catalytic solution for combining both approaches. The Ru-Na2CO3 DFM deposited on Al2O3 captures CO2 from a flue gas and catalytically converts it to synthetic natural gas (i.e., methane) using H2 generated from renewable sources. The Ru in the DFM, in combination with H2, catalytically hydrogenates both adsorbed CO2 and the bulk Na2CO3, forming methane. The depleted sites adsorb CO2 through a carbonate reformation process and in addition adsorb CO2 on its surface. This material functions well in O2- and H2O-containing flue gas where the favorable Ru redox property allows RuOx, formed during flue gas exposure, to be reduced during the hydrogenation cycle. As a combined CO2 capture and utilization scheme, this technology overcomes many of the limitations of the conventional liquid amine-based CO2 sorbent technology.