| 1. |
- Budnyak, Tetyana M., et al.
(författare)
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Chitosan Deposited onto Fumed Silica Surface as Sustainable Hybrid Biosorbent for Acid Orange 8 Dye Capture : Effect of Temperature in Adsorption Equilibrium and Kinetics
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:28, s. 15312-15323
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Tidskriftsartikel (refereegranskat)abstract
- Chitosan was deposited on fumed silica without the addition of cross-linkers or activating agents. The chitosan surface layer has a high affinity toward organic molecules, e.g., Acid Orange 8 (AO8) dye, robust to a broad range of simulated conditions (variance with respect to temperature, time, and concentration of solute). Experimental equilibrium data were analyzed by the generalized Langmuir equation taking into consideration the energetic heterogeneity of the adsorption system. The effect of temperature on dye uptake and adsorption rate was studied. According to the calculated thermodynamic functions Delta G degrees, Delta H degrees, and Delta S degrees from the equilibrium data at different temperatures, the adsorption of AO8 onto chitosan-fumed silica composite is exothermic and spontaneous. The studies of temperature effect on adsorption equilibrium show that the maximum adsorption capacity (determined from the Langmuir-Freundlich equation) of synthesized composite toward AO8 is about one-third higher in the case of an isotherm measured at 5 degrees C than this value obtained for the isotherm measured at 45 degrees C. The quantitative binding of dye molecules to chitosan coating on the surface of silica was proved by H-1 MAS NMR. The deep kinetics study through the application of various theoretical models-the first-order equation, pseudo-first-order equation, second-order equation, pseudo-second-order equation, mixed first, second-order equation, and multiexponential equation-was applied for getting inside the mechanism of AO8 binding to the chitosan coating. Structural characteristics of chitosan-coated silica were obtained from the low-temperature adsorption/desorption isotherms of nitrogen and imaging by scanning electron microscopy. The effects of a synthetic route for polymer coating on thermal stability and the ability to degrade were studied by differential scanning calorimetry.
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| 2. |
- Budnyak, Tetyana M., et al.
(författare)
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Lignin-Inorganic Interfaces : Chemistry and Applications from Adsorbents to Catalysts and Energy Storage Materials
- 2020
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 13:17, s. 4344-4355
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Forskningsöversikt (refereegranskat)abstract
- Lignin is one the most fascinating natural polymers due to its complex aromatic‐aliphatic structure. Phenolic hydroxyl and carboxyl groups along with other functional groups provide technical lignins with reactivity and amphiphilic character. Many different lignins have been used as functional agents to facilitate the synthesis and stabilization of inorganic materials. Herein, the use of lignin in the synthesis and chemistry of inorganic materials in selected applications with relevance to sustainable energy and environmental fields is reviewed. In essence, the combination of lignin and inorganic materials creates an interface between soft and hard materials. In many cases it is either this interface or the external lignin surface that provides functionality to the hybrid and composite materials. This Minireview closes with an overview on future directions for this research field that bridges inorganic and lignin materials for a more sustainable future.
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| 3. |
- Budnyak, Tetyana M., et al.
(författare)
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Membrane-Filtered Kraft Lignin-Silica Hybrids as Bio-Based Sorbents for Cobalt(II) Ion Recycling
- 2020
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 5:19, s. 10847-10856
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Tidskriftsartikel (refereegranskat)abstract
- Efficient and sustainable recycling of cobalt(II) is of increasing importance to support technological development in energy storage and electric vehicle industries. A composite material based on membrane-filtered lignin deposited on nanoporous silica microparticles was found to be an effective and sustainable sorbent for cobalt(II) removal. This bio-based sorbent exhibited a high sorption capacity, fast kinetics toward cobalt(II) adsorption, and good reusability. The adsorption capacity was 18 mg Co(II) per gram of dry adsorbent at room temperature (22 degrees C) at near-neutral pH, three times higher than that of the summarized capacity of lignin or silica starting materials. The kinetics study showed that 90 min is sufficient for effective cobalt(II) extraction by the composite sorbent. The pseudo-second-order kinetics and Freundlich isotherm models fitted well with experimentally obtained data and confirmed heterogeneity of adsorption sites. The promising potential of the lignin-silica composites for industrial applications in the cobalt recovering process was confirmed by high values of desorption in mildly acidic solutions.
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| 4. |
- Budnyak, Tetyana M., et al.
(författare)
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Tailored Hydrophobic/Hydrophilic Lignin Coatings on Mesoporous Silica for Sustainable Cobalt(II) Recycling
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:43, s. 16262-16273
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Tidskriftsartikel (refereegranskat)abstract
- Lignin is a renewable biopolymer, and its chemical functionalization renders it a prospective material for a plethora of applications. Within this respect, we present a method for lignin immobilization on the surface of mesoporous silica. Two types of lignins were used to prove the feasibility of the fabrication of either hydrophilic or hydrophobic biocoatings on silica. The procedure permits to immobilize 17 mg of lignosulfonate (LS) or 37 mg of kraft lignin (KL) per gram of silica. The bioinorganic composites display a synergistic effect in the adsorption of cobalt(II) ions from aqueous solutions because the adsorption efficiency outperforms the individual constituents. These results demonstrate that thin lignin overlayers, exhibiting polymer concentrations of 0.07 mg.m(-2) for LS-SiO2, and 0.14 mg.m(-2) for KL-SiO2, provide new functionality in comparison to bulk lignin and metal oxides. According to the Langmuir isotherm model, the adsorption capacity toward aqua complexes of Co(II) was found to be 75 and 59 mg.g(-1) for the LS- or KL-coated silica, respectively. The kinetic study revealed that lignin-SiO2 composites gained the features of inorganic sorbents because 1-1.5 h was sufficient for effective cobalt extraction. The adsorption on the bioinorganic composites proceeds with the pseudo-second-order kinetics model. The adsorption of Co(II) ions was confirmed by means of solid-state H-1 magic-angle spinning (MAS) NMR spectroscopy. The simplicity of the synthesis, low-cost and abundancy of substrates, high capacity, and fast kinetics make such lignin-coated silica a promising material for cobalt recovery.
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| 5. |
- Chen, Zheng, et al.
(författare)
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Increased photocurrent of CuWO4 photoanodes by modification with the oxide carbodiimide Sn2O(NCN)
- 2020
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:11, s. 3450-3456
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Tidskriftsartikel (refereegranskat)abstract
- Tin(ii) oxide carbodiimide is a novel prospective semiconductor material with a band gap of 2.1 eV and lies chemically between metal oxides and metal carbodiimides. We report on the photochemical properties of this oxide carbodiimide and apply the material to form a heterojunction with CuWO4 thin films for photoelectrochemical (PEC) water oxidation. Mott-Schottky experiments reveal that the title compound is an n-type semiconductor with a flat-band potential of -0.03 V and, as such, the position of the valence band edge would be suitable for photochemical water oxidation. Sn2O(NCN) increases the photocurrent of CuWO4 thin films from 32 mu A cm(-2) to 59 mu A cm(-2) at 1.23 V vs. reversible hydrogen electrode (RHE) in 0.1 M phosphate buffer (pH 7.0) under backlight AM 1.5G illumination. This upsurge in photocurrent originates in a synergistic effect between the oxide and oxide carbodiimide, because the heterojunction photoanode displays a higher current density than the sum of its individual components. Structural analysis by powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) reveals that Sn2O(NCN) forms a core-shell structure Sn2O(NCN)@SnPOx during the PEC water oxidation in phosphate buffer. The electrochemical activation is similar to the behavior of Mn(NCN) but different from Co(NCN).
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| 6. |
- Chen, Zheng, et al.
(författare)
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Tailoring the Surface Properties of Bi2O2NCN by in Situ Activation for Augmented Photoelectrochemical Water Oxidation on WO3 and CuWO4 Heterojunction Photoanodes
- 2020
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 59:18, s. 13589-13597
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Tidskriftsartikel (refereegranskat)abstract
- Bismuth(III) oxide-carbodiimide (Bi2O2NCN) has been recently discovered as a novel mixed-anion semiconductor, which is structurally related to bismuth oxides and oxysulfides. Given the structural versatility of these layered structures, we investigated the unexplored photochemical properties of the target compound for photoelectrochemical (PEC) water oxidation. Although Bi2O2NCN does not generate a noticeable photocurrent as a single photoabsorber, the fabrication of heterojunctions with the WO3 thin film electrode shows an upsurge of current density from 0.9 to 1.1 mA cm–2 at 1.23 V vs reversible hydrogen electrode (RHE) under 1 sun (AM 1.5G) illumination in phosphate electrolyte (pH 7.0). Mechanistic analysis and structural analysis using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (STEM EDX) indicate that Bi2O2NCN transforms during operating conditions in situ to a core–shell structure Bi2O2NCN/BiPO4. When compared to WO3/BiPO4, the in situ electrolyte-activated WO3/Bi2O2NCN photoanode shows a higher photocurrent density due to superior charge separation across the oxide/oxide-carbodiimide interface layer. Changing the electrolyte from phosphate to sulfate results in a lower photocurrent and shows that the electrolyte determines the surface chemistry and mediates the PEC activity of the metal oxide-carbodiimide. A similar trend could be observed for CuWO4 thin film photoanodes. These results show the potential of metal oxide-carbodiimides as relatively novel representatives of mixed-anion compounds and shed light on the importance of the control over the surface chemistry to enable the in situ activation.
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| 7. |
- de Bruin-Dickason, Caspar, et al.
(författare)
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Valorisation of used lithium-ion batteries into nanostructured catalysts for green hydrogen from boranes
- 2020
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Ingår i: Materials Advances. - : Royal Society of Chemistry (RSC). - 2633-5409. ; 1:7, s. 2279-2285
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Tidskriftsartikel (refereegranskat)abstract
- Cobalt-based Li-ion batteries are produced globally on a massive scale, but most are discarded to landfill at the end of their useful lifetime. In this work, an efficient cobalt catalyst for the hydrolysis of sodium borohydride to dihydrogen was prepared from lithium ion battery waste, providing a second life for valuable minerals. This material is composed of a mixed metal cobalt-aluminium oxide supported on graphene, as elucidated by a combined FTIR, Raman, SEM, scanning transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) and energy-dispersive X-ray spectroscopy (EDS) study. The obtained metal oxide material, which exhibits an average oxidation state for Co of 2.45, is a languid catalyst at room temperature, but rapid hydrogen production of up to 49 L(H-2) min(-1) g(-1)(Co) was observed in catalytic runs heated to 70 degrees C. This carbon-supported cobalt catalyst is competitive with designed cobalt nanostructured catalysts prepared from pure precursors. This work is illustrative of the opportunities which arise when e-waste is utilised as a mineral resource within the scope of a circular economy.
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| 8. |
- Guo, Hua, et al.
(författare)
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Trapping of different stages of BaTiO3 reduction with LiH
- 2020
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 10:58, s. 35356-35365
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the hydride reduction of tetragonal BaTiO3 using LiH. The reactions employed molar H : BaTiO3 ratios of 1.2, 3, and 10 and variable temperatures up to 700 °C. The air-stable reduced products were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy, thermogravimetric analysis (TGA), X-ray fluorescence (XRF), and 1H magic-angle spinning (MAS) NMR spectroscopy. Effective reduction, as indicated by the formation of dark blue to black colored, cubic-phased, products was observed at temperatures as low as 300 °C. The product obtained at 300 °C corresponded to oxyhydride BaTiO∼2.9H∼0.1, whereas reduction at higher temperatures resulted in simultaneous O defect formation, BaTiO2.9−xH0.1□x, and eventually – at temperatures above 450 °C – to samples void of hydridic H. Concomitantly, the particles of samples reduced at high temperatures (500–600 °C) display substantial surface alteration, which is interpreted as the formation of a TiOx(OH)y shell, and sintering. Diffuse reflectance UV-VIS spectroscopy shows broad absorption in the VIS-NIR region, which is indicative of the presence of n-type free charge carriers. The size of the intrinsic band gap (∼3.2 eV) appears only slightly altered. Mott–Schottky measurements confirm the n-type conductivity and reveal shifts of the conduction band edge in the LiH reduced samples. Thus LiH appears as a versatile reagent to produce various distinct forms of reduced BaTiO3 with tailored electronic properties.
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| 9. |
- Lu, Can, et al.
(författare)
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Nanostructured core-shell metal borides-oxides as highly efficient electrocatalysts for photoelectrochemical water oxidation
- 2020
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 12:5, s. 3121-3128
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen evolution reaction (OER) catalysts are critical components of photoanodes for photoelectrochemical (PEC) water oxidation. Herein, nanostructured metal boride MB (M = Co, Fe) electrocatalysts, which have been synthesized by a Sn/SnCl2 redox assisted solid-state method, were integrated with WO3 thin films to build heterojunction photoanodes. As-obtained MB modified WO3 photoanodes exhibit enhanced charge carrier transport, amended separation of photogenerated electrons and holes, prolonged hole lifetime and increased charge carrier density. Surface modification of CoB and FeB significantly enhances the photocurrent density of WO3 photoanodes from 0.53 to 0.83 and 0.85 mA cm(-2), respectively, in transient chronoamperometry (CA) at 1.23 V vs. RHE (V-RHE) under interrupted illumination in 0.1 M Na2SO4 electrolyte (pH 7), corresponding to an increase of 1.6 relative to pristine WO3. In contrast, the pristine MB thin film electrodes do not produce noticeable photocurrent during water oxidation. The metal boride catalysts transform in situ to a core-shell structure with a metal boride core and a metal oxide (MO, M = Co, Fe) surface layer. When coupled to WO3 thin films, the CoB@CoOx nanostructures exhibit a higher catalytic enhancement than corresponding pure cobalt borate (Co-B-i) and cobalt hydroxide (Co(OH)(x)) electrocatalysts. Our results emphasize the role of the semiconductor-electrocatalyst interface for photoelectrodes and their high dependency on materials combination.
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| 10. |
- Lu, Can, et al.
(författare)
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NiO/Poly(4-alkylthiazole) Hybrid Interface for Promoting Spatial Charge Separation in Photoelectrochemical Water Reduction
- 2020
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:26, s. 29173-29180
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Tidskriftsartikel (refereegranskat)abstract
- Conjugated polymers are emerging as alternatives to inorganic semiconductors for the photoelectrochemical water splitting. Herein, semi-transparent poly(4-alkylthiazole) layers with different trialkylsilyloxymethyl (R3SiOCH2-) side chains (PTzTNB, R = n-butyl; PTzTHX, R = n-hexyl) are applied to functionalize NiO thin films to build hybrid photocathodes. The hybrid interface allows for the effective spatial separation of the photoexcited carriers. Specifically, the PTzTHX-deposited composite photocathode increases the photocurrent density 6- and 2-fold at 0 V versus the reversible hydrogen electrode in comparison to the pristine NiO and PTzTHX photocathodes, respectively. This is also reflected in the substantial anodic shift of onset potential under simulated Air Mass 1.5 Global illumination, owing to the prolonged lifetime, augmented density, and alleviated recombination of photogenerated electrons. Additionally, coupling the inorganic and organic components also enhances the photoabsorption and amends the stability of the photocathode-driven system. This work demonstrates the feasibility of poly(4-alkylthiazole)s as an effective alternative to known inorganic semiconductor materials. We highlight the interface alignment for polymer-based photoelectrodes.
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| 11. |
- Ma, Zili, et al.
(författare)
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Elucidation of the Active Sites for Monodisperse FePt and Pt Nanocrystal Catalysts for p-WSe2 Photocathodes
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:22, s. 11877-11885
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Tidskriftsartikel (refereegranskat)abstract
- The two-dimensional p-type semiconductor WSe2 is a promising candidate for photo-electrochemical (PEC) H-2 generation. Despite its high absorption coefficient, the PEC hydrogen evolution reaction (HER) efficiency is low and necessitates a catalyst to achieve higher photocurrents. Here, we investigate the monodisperse spherical alloy FePt and pure Pt nanocrystals (NCs) as catalysts for the PEC HER on p-WSe2 single-crystal photocathodes. After deposition of Pt or FePt, photocurrents of -0.27 and -4.0 mA cm(-2) at 0 V versus the reversible hydrogen electrode were achieved for the HER, which were 7.4 and 15 times higher compared to pristine WSe2 single crystals, respectively. Calculations at the density functional theory level show that the water adsorption and thus enhanced H2O dissociation are preferential on FePt in comparison to Pt. The edge sites of both Pt and FePt have a more negative adsorption energy than the (111) and (100) facets, indicating that the edges are the preferential sites for hydrogen production. The computational results show that the size of the Pt NC, within the range of Pt-55 (1.1 nm) and Pt-147 (1.6 nm), does not significantly influence the mechanism for the HER on the NCs.
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| 12. |
- Ma, Zili, et al.
(författare)
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Exploring the Origins of Improved Photocurrent by Acidic Treatment for Quaternary Tantalum-Based Oxynitride Photoanodes on the Example of CaTaO2N
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:1, s. 152-160
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Tidskriftsartikel (refereegranskat)abstract
- Quaternary tantalum-based oxynitrides ATa(O,N)(3),with electronic band gaps between 1.8 and 2.4 eV, are promising materials for photochemical water-splitting. The tailoring of their surface properties is a critical aspect to obtain efficient hole extraction. We report on the origin of improved photoelectrochemical (PEC) water oxidation by means of acidic treatment for this class of compounds on the example of cubic CaTaO2N particles. We address the effect of acidic treatment by using complementary physical characterization techniques, such as X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, H-1 and N-1 solid-state nuclear magnetic resonance (NMR) spectroscopy, electron microscopy, and electronic band structure calculations at the density functional theory level. In combination with PEC measurements, solid-state NMR indicates that the restructured surface displays a meaningfully higher concentration of terminating OH groups. Subsequent deposition of a nickel borate (NiBi;) catalyst on the acid-treated surface yields a higher percentual upsurge of photocurrent in comparison to pristine CaTaO2N. Our results highlight the application of solid-state NMR spectroscopy for understanding the semiconductor-catalyst interface in photochemical devices.
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| 13. |
- Ma, Zili, et al.
(författare)
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Semi-transparent quaternary oxynitride photoanodes on GaN underlayers
- 2020
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 56:86, s. 13193-13196
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Tidskriftsartikel (refereegranskat)abstract
- Conformal atomic layer deposition (ALD) technique is employed to make semi-transparent TaOxNy, providing the possibility to build semi-transparent oxy(nitride) heterojunction photoanodes on conductive substrates. A generalized approach was developed to manufacture semi-transparent quaternary metal oxynitrides on conductive substrates beyond semi-transparent binary Ta3N5 photoanodes aiming for wireless tandem photoelectrochemical (PEC) cells.
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| 14. |
- Ma, Zili, et al.
(författare)
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Structural evolution of CrN nanocube electrocatalysts during nitrogen reduction reaction
- 2020
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 12:37, s. 19276-19283
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Tidskriftsartikel (refereegranskat)abstract
- Metal nitrides have been suggested as prospective catalysts for the electrochemical nitrogen reduction reaction (NRR) in order to obtain ammonia at room temperature under ambient pressure. Herein, we report that templated chromium nitride porous microspheres built up by nanocubes (NCs) are an efficient noble-metal-free electrocatalyst for NRR. The CrN NCs catalyst exhibits both a high stability and NH(3)yield of 31.11 mu g h(-1)mg(cat.)(-1)with a Faradaic efficiency (FE) of 16.6% in 0.1 M HCl electrolyte. Complementary physical characterization techniques demonstrate partial oxidation of the pristine CrN NCs during reaction. Structural characterization by means of scanning transmission electron microscopy (STEM) combining electron energy loss spectrum (EELS) and energy dispersive X-ray spectroscopy (EDX) analysis reveals the NC structure to consist of an O-rich core and N-rich shell after NRR. This gradient distribution of nitrogen within the CrN NCs upon completed NRR is distinct to previously reported metal nitride NRR catalysts, because no significant loss of nitrogen occurs at the catalyst surface.
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| 15. |
- Nair, Santhosh S., et al.
(författare)
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Converting cellulose nanocrystals into photocatalysts by functionalisation with titanium dioxide nanorods and gold nanocrystals
- 2020
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 10:61, s. 37374-37381
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanocrystals (CNCs) are promising building blocks for water purification due to their high surface area, tuneability of surface charge and grafting of surface groups depending on the pollutants. In this report we have converted CNCs into photocatalysts, without altering the surface groups, byin situgrowth of TiO(2)nanorods (NRs) and functionalization with Au nanocrystals (NCs) for enhanced light absorption. The control of the density of the NRs assures that the CNC surface and functionalities are accessible for the pollutant, followed by the photocatalytic degradation on the light absorption layer under solar illumination. This seed-mediated NR synthesis can be applied to realize a series of CNC-inorganic NR photocatalysts. The low temperature (90 degrees C compared to commonly reported growth at 150 degrees C) of the NR growth provides the opportunity to use nanostructured biopolymers as functional substrates for preparation of photocatalysts using a bio-inspired design.
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| 16. |
- Onwumere, Joy, et al.
(författare)
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CelluPhot : Hybrid Cellulose-Bismuth Oxybromide Membrane for Pollutant Removal
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : NLM (Medline). - 1944-8244 .- 1944-8252. ; 12:38, s. 42891-42901
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Tidskriftsartikel (refereegranskat)abstract
- The simultaneous removal of organic and inorganic pollutants from wastewater is a complex challenge and requires usually several sequential processes. Here, we demonstrate the fabrication of a hybrid material that can fulfill both tasks: (i) the adsorption of metal ions due to the negative surface charge, and (ii) photocatalytic decomposition of organic compounds. The bioinorganic hybrid membrane consists of cellulose fibers to ensure mechanical stability and of Bi4O5Br2/BiOBr nanosheets. The composite is synthesized at low temperature of 115 °C directly on the cellulose membrane (CM) in order to maintain the carboxylic and hydroxyl groups on the surface that are responsible for the adsorption of metal ions. The composite can adsorb both Co(II) and Ni(II) ions and the kinetic study confirmed a good agreement of experimental data with the pseudo-second-order equation kinetic model. CM/Bi4O5Br2/BiOBr showed higher affinity to Co(II) ions than to Ni(II) ions from diluted aqueous solutions. The bioinorganic composite demonstrates a synergistic effect in the photocatalytic degradation of rhodamine B (RhB) by exceeding the removal efficiency of single components. The fabrication of the biologic-inorganic interface was confirmed by various analytical techniques including scanning electron microscopy (SEM), scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM EDX) mapping, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The presented approach for controlled formation of the bioinorganic interface between natural material (cellulose) and nanoscopic inorganic materials of tailored morphology (Bi-O-Br system) enables the significant enhancement of materials functionality.
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| 17. |
- Piątek, Jędrzej, et al.
(författare)
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Glycine-functionalized silica as sorbent for cobalt(II) and nickel(II) recovery
- 2020
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 530
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Tidskriftsartikel (refereegranskat)abstract
- We disclose that glycine functionalized silica particles (SiO2-Gly) are highly effective sorbents for the removal of Co(II) and Ni(II) ions from aqueous solution. SiO2-Gly can be prepared from commercial silica gel in a high yielding two step synthesis, and features a glycine concentration of 0.63 mmol.g(-1) (27 mmol.cm(-2)). This material can recover up to 2.81 mmol.g(-1) of Co(II) ions or 3.02 mmol.g(-1) of Ni(II) ions from aqueous solution, a capacity which is tenfold higher than unmodified silica and comparable to the best performing sorbents reported in the literature. These sorption capacities are superstoichiometric in relation to the concentration of glycine on the surface. Sorption of cobalt(II) was improved by addition of ammonia to leaching solutions to give rise to more readily absorbed cobalt amine complexes. Regeneration of sorbent was investigated by desorption of adsorbed metals under mildly acidic solutions, and efficient desorption was noted for both metals. To probe the mechanism of sorption, a thorough characterization campaign involving TGA, FTIR, nitrogen adsorption/desorption, SEM, solid state NMR, solid state UV-Vis-NIR, -COOH titration and pH(pzc) - pH drift methods was undertaken. Our mechanistic study indicated that adsorption was mediated by electrostatic interaction.
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| 18. |
- Qiao, Xianji, et al.
(författare)
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Metathetic synthesis of lead cyanamide as a p-type semiconductor
- 2020
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:40, s. 14061-14067
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Tidskriftsartikel (refereegranskat)abstract
- Lead cyanamide PbNCN was synthesized by solid-state metathesis between PbCl2 and Na2NCN in a 1 : 1 molar ratio, and its structure was confirmed from Rietveld refinement of X-ray data. Electronic-structure calculations of HSE06 density-functional type reveal PbNCN to be an indirect semiconductor with a band gap of 2.4 eV, in remarkable quantitative agreement with the measured value. Mott-Schottky experiments demonstrate PbNCN to be a p-type semiconductor with a flat-band potential of 2.3 eV vs. the reversible hydrogen electrode (RHE) which is commonly used to estimate the value of the valence band edge position. Moreover, thin films of powderous PbNCN were assembled into a photoelectrode for photoelectrochemical water splitting. On the example of p-type PbNCN, this study provides the first experimental evidence that MNCN compounds can be applied as photocathodes for reductive reactions in photoelectrochemical cells.
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| 19. |
- Subasi, Yaprak, et al.
(författare)
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Surface modified TiO2/reduced graphite oxide nanocomposite anodes for lithium ion batteries
- 2020
-
Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1432-8488 .- 1433-0768. ; 24:5, s. 1085-1093
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Tidskriftsartikel (refereegranskat)abstract
- Anatase TiO2 nanoparticles with an average crystallite size of ~ 20 nm are synthesized through a sol-gel method. A composite anode for Li-ion batteries is prepared with the synthesized TiO2 nanoparticles and reduced graphite oxide (RGO) as the conductive carbon source. After the preparation of TiO2/RGO nanocomposite, a novel surface modification is carried out by the employment of H2O2 to enhance the overall electrochemical performance of nanocomposite anode (TiO2/RGO-P composite). The physical and chemical characterizations of the surface modified TiO2/RGO-P composites are performed with X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) analyses. The electrochemical performance of TiO2/RGO-P composite electrodes is investigated via galvanostatic charge-discharge cycling tests in a potential window of 1.0-3.0 V. Compared to the plain TiO2/RGO composite anode, the TiO2/RGO-P composite anode has higher reversible capacities and better cycling performance due to the enhanced and stable formation of 3D channels of TiO2 nanoparticles with RGO stemming from the surface modification with H2O2. The TiO2/RGO-P composite anode delivers reversible discharge capacities around 291 mA h g(-1) at a rate of 100 mA g(-1), whereas the value stays at 214 and 143 mA h g(-1) for the plain TiO2/RGO composite and TiO2 nanoparticle without any RGO, respectively.
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| 20. |
- Szewczyk, Ireneusz, et al.
(författare)
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Electrochemical Denitrification and Oxidative Dehydrogenation of Ethylbenzene over N-doped Mesoporous Carbon : Atomic Level Understanding of Catalytic Activity by N-15 NMR Spectroscopy
- 2020
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 32:17, s. 7263-7273
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Tidskriftsartikel (refereegranskat)abstract
- Spherical mesoporous carbon (with a particle size in the range of 40−75 μm) was synthesized by nanoreplication of a hard silica template using sucrose as the carbon precursor. The mesoporous carbon with BET surface areas higher than 1200 m2/g was doped with N by a treatment in an aqueous solution of nitric acid and/or in a flow of gaseous ammonia. The highest N content (3.2 wt % of N in bulk) was obtained when both modification methods were combined. Complementary physicochemical characterization techniques, including scanning electron microscopy (SEM), low-temperature N2 adsorption, powder X-ray diffraction (XRD), and Raman spectroscopy revealed the morphology, structure, and textural properties of the synthesized N-loaded carbon materials. For the identification of the detailed chemical structure on the surface of the carbons, 1H, 13C, and 15N solid-state nuclear magnetic resonance (NMR) measurements were performed, and the data were supported by chemical shift calculations with accurate quantum chemistry methods and X-ray photoelectron spectroscopic (XPS) analyses. All NMR experiments were performed at natural isotope abundance. The verified experimental data clearly showed that after the introduction of the N-containing moieties by the combined methods of treatment, a high concentration of pyridinic N at the edge, and pyrrolic N being external to the edge, was achieved for the mesoporous carbon. The distributed N surface species promoted the catalytic activity in the oxidative dehydrogenation of ethylbenzene to styrene but did not significantly influence the efficiency of the carbon materials in the electrochemical reduction of nitrate ions.
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| 21. |
- Thersleff, Thomas, et al.
(författare)
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Dissecting complex nanoparticle heterostructures via multimodal data fusion with aberration-corrected STEM spectroscopy
- 2020
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 219
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Tidskriftsartikel (refereegranskat)abstract
- With nanostructured materials such as catalytic heterostructures projected to play a critical role in applications ranging from water splitting to energy harvesting, tailoring their properties to specific tasks requires an increasingly comprehensive characterization of their local chemical and electronic landscape. Although aberration-corrected electron spectroscopy currently provides sufficient spatial resolution to study this space, an approach to concurrently dissect both the electronic structure and full composition of buried metal/oxide interfaces remains a considerable challenge. In this manuscript, we outline a statistical methodology to jointly analyze simultaneously-acquired STEM EELS and EDX datasets by fusing them along their shared spatial factors. We show how this procedure can be used to derive a rich descriptive model for estimating both transition metal valency and full chemical composition from encapsulated morphologies such as core-shell nanoparticles. We demonstrate this on a heterogeneous Co-P thin film catalyst, concluding that this system is best described as a multi-shell phosphide structure with a P-doped metallic Co core.
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| 22. |
- Yakymovych, Andriy, et al.
(författare)
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Nanocomposite SAC solders : the effect of adding CoPd nanoparticles on the morphology and the shear strength of the Sn–3.0Ag–0.5Cu/Cu solder joints
- 2020
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Ingår i: Applied Nanoscience. - : Springer Science and Business Media LLC. - 2190-5509 .- 2190-5517. ; 10, s. 4603-4607
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Tidskriftsartikel (refereegranskat)abstract
- The effect of bimetallic monodisperse CoPd nanoparticles on the microstructure and the shear strength of the Cu/ SAC305/Cu solder joint was investigated. The nanocomposite Sn–3.0Ag–0.5Cu (SAC305) solders with 0.1, 0.3, 0.5, and 1.0 wt% nanoCoPd were prepared through a paste mixing method. The employed bimetallic nanoparticles were produced via a modified oleylamine method. The microstructural analysis of as-solidified Cu/solder/Cu joints was performed by scanning electron microscopy. The results showed that initial additions of CoPd nanoparticles into the SAC305 solder promoted the growth of the interfacial planar-type Cu3Sn IMC layer; while the average thickness of the interfacial scallop-type Cu6Sn5 IMC layer slightly decreased. Further additions of the nanosized CoPd admixtures to the SAC305 solder paste lead to a significant increase of the average thickness of the Cu6Sn5 intermetallic compound layer up to 40%. The shear strength measurements were performed to investigate a relationship between the microstructure and mechanical properties of the investigated solder joints. The results indicated a decrease in the shear strength of the SAC305 solder joint by addition of 0.1 wt% CoPd NPs, while a difference in absolute values between solder joints with 0.3, 0.5, and 1.0 wt% nanoCoPd was practically insignificant.
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