| 1. |
- Berniak, Tomasz, et al.
(författare)
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Covalent bonding of N-hydroxyphthalimide on mesoporous silica for catalytic aerobic oxidation of p-xylene at atmospheric pressure
- 2024
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Ingår i: ChemPlusChem. - 2192-6506.
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Tidskriftsartikel (refereegranskat)abstract
- The surface of SBA-15 mesoporous silica was modified by N-hydroxyphthalimide (NHPI) moieties acting as immobilized active species for aerobic oxidation of alkylaromatic hydrocarbons. The incorporation was carried out by four original approaches: the grafting-from and grafting-onto techniques, using the presence of surface silanols enabling the formation of particularly stable O-Si-C bonds between the silica support and the organic modifier. The strategies involving the Heck coupling led to the formation of NHPI groups separated from the SiO2 surface by a vinyl linker, while one of the developed modification paths based on the grafting of an appropriate organosilane coupling agent resulted in the active phase devoid of this structural element. The successful course of the synthesis was verified by FTIR and H-1 NMR measurements. Furthermore, the formed materials were examined in terms of their chemical composition (elemental analysis, thermal analysis), structure of surface groups (C-13 NMR, XPS), porosity (low-temperature N-2 adsorption), and tested as catalysts in the aerobic oxidation of p-xylene at atmospheric pressure. The highest conversion and selectivity to p-toluic acid were achieved using the catalyst with enhanced availability of non-hydrolyzed NHPI groups in the pore system. The catalytic stability of the material was additionally confirmed in several subsequent reaction cycles.
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| 2. |
- Budnyak, Tetyana, et al.
(författare)
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LignoPhot : Conversion of hydrolysis lignin into the photoactive hybrid lignin/Bi4O5Br2/BiOBr composite for simultaneous dyes oxidation and Co2+ and Ni2+ recycling
- 2021
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 279
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Tidskriftsartikel (refereegranskat)abstract
- Valorization of lignin is still an open question and lignin has therefore remained an underutilized biomaterial. This situation is even more pronounced for hydrolysis lignin, which is characterized by a highly condensed and excessively cross-linked structure. We demonstrate the synthesis of photoactive lignin/Bi4O5Br2/BiOBr bio-inorganic composites consisting of a lignin substrate that is coated by semiconducting nanosheets. The XPS analysis reveals that growing these nanosheets on lignin instead on cellulose prevents the formation of Bi5+ ions at the surface region, yielding thus a modified hetero-junction Bi4O5Br2/BiOBr. The material contains 18.9% of Bi4O5Br2/BiOBr and is effective for the photocatalytic degradation of cationic methylene blue (MB) and zwitterionic rhodamine B (RhB) dyes under light irradiation. Lignin/Bi4O5Br2/BiOBr decreases the dye concentration from 80 mg L-1 to 12.3 mg L-1 for RhB (85%) and from 80 mg L-1 to 4.4 mg L-1 for MB (95%). Complementary to the dye degradation, the lignin as a main component of the composite, was found to be efficient and rapid biosorbent for nickel, lead, and cobalt ions. The low cost, stability and ability to simultaneously photo-oxidize organic dyes and adsorb metal ions, make the photoactive lignin/Bi4O5Br2/BiOBr composite a prospective material for textile wastewaters remediation and metal ions recycling.
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| 3. |
- Chen, Zheng, et al.
(författare)
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Graphitic nitrogen in carbon catalysts is important for the reduction of nitrite as revealed by naturally abundant N-15 NMR spectroscopy
- 2021
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; :20
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Tidskriftsartikel (refereegranskat)abstract
- Metal-free nitrogen-doped carbon is considered as a green functional material, but the structural determination of the atomic positions of nitrogen remains challenging. We recently demonstrated that directly-excited solid state N-15 NMR (ssNMR) spectroscopy is a powerful tool for the determination of such positions in N-doped carbon at natural N-15 isotope abundance. Here we report a green chemistry approach for the synthesis of N-doped carbon using cellulose as a precursor, and a study of the catalytic properties and atomic structures of the related catalyst. N-doped carbon (NH3) was obtained by the oxidation of cellulose with HNO3 followed by ammonolysis at 800 degrees C. It had a N content of 6.5 wt% and a surface area of 557 m(2) g(-1), and N-15 ssNMR spectroscopy provided evidence for graphitic nitrogen besides regular pyrrolic and pyridinic nitrogen. This structural determination allowed probing the role of graphitic nitrogen in electrocatalytic reactions, such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and nitrite reduction reaction. The N-doped carbon catalyst (NH3) showed higher electrocatalytic activities in the OER and HER under alkaline conditions and higher activity for nitrite reduction, as compared with a catalyst prepared by the carbonization of HNO3-treated cellulose in N-2. The electrocatalytic selectivity for nitrite reduction of the N-doped carbon catalyst (NH3) was directly related to the graphitic nitrogen functions. Complementary structural analyses by means of C-13 and H-1 ssNMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and low-temperature N-2 adsorption were performed and provided support to the findings. The results show that directly-excited N-15 ssNMR spectroscopy at natural N-15 abundance is generally capable of providing information on N-doped carbon materials if relaxation properties are favorable. It is expected that this approach can be applied to a wide range of solids with an intermediate concentration of N atoms.
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| 4. |
- 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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| 5. |
- Chen, Zheng, et al.
(författare)
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Reaction pathways on N-substituted carbon catalysts during the electrochemical reduction of nitrate to ammonia
- 2022
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Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry. - 2044-4753 .- 2044-4761. ; 12:11, s. 3582-3593
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical reduction of nitrate into ammonia is one potential strategy to valorize pollutants needed to close the nitrogen cycle. The understanding of carbonaceous materials as metal-free representatives of electrocatalysts is of high importance to ensure sufficient activity and target selectivity. We report on the role of defects in cellulose-derived nitrogen-doped carbon (NDC) materials, produced by ammonolysis at different temperatures, to obtain efficient electrocatalysts for the nitrate reduction reaction (NO3RR). Carbon catalyst ammonolysis at 800 °C (NDC-800) yields the highest electrochemical performance, exhibiting 73.1% NH4+ selectivity and nearly 100% NO3− reduction efficiency with a prolonged NO3RR time (48 h) at −1.5 V vs. Ag/AgCl in a 0.1 M Na2SO4 electrolyte. We provide support to our findings by undertaking complementary structural analyses with scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, low-temperature N2 adsorption, and theoretical studies based on multi-scale/level calculations. Atomistic molecular dynamics simulations based on a reactive force field combined with quantum chemistry (QC) calculations on representative model systems suggest possible realistic scenarios of the material structure and reaction mechanisms of the NO3− reduction routes.
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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. |
- Gopakumar, Aswin, et al.
(författare)
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Lignin-Supported Heterogeneous Photocatalyst for the Direct Generation of H2O2 from Seawater
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:6, s. 2603-2613
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Tidskriftsartikel (refereegranskat)abstract
- The development of smart and sustainable photocatalysts is in high priority for the synthesis of H2O2 because the global demand for H2O2 is sharply rising. Currently, the global market share for H2O2 is around 4 billion US$ and is expected to grow by about 5.2 billion US$ by 2026. Traditional synthesis of H2O2 via the anthraquinone method is associated with the generation of substantial chemical waste as well as the requirement of a high energy input. In this respect, the oxidative transformation of pure water is a sustainable solution to meet the global demand. In fact, several photocatalysts have been developed to achieve this chemistry. However, 97% of the water on our planet is seawater, and it contains 3.0–5.0% of salts. The presence of salts in water deactivates the existing photocatalysts, and therefore, the existing photocatalysts have rarely shown reactivity toward seawater. Considering this, a sustainable heterogeneous photocatalyst, derived from hydrolysis lignin, has been developed, showing an excellent reactivity toward generating H2O2 directly from seawater under air. In fact, in the presence of this catalyst, we have been able to achieve 4085 μM of H2O2. Expediently, the catalyst has shown longer durability and can be recycled more than five times to generate H2O2 from seawater. Finally, full characterizations of this smart photocatalyst and a detailed mechanism have been proposed on the basis of the experimental evidence and multiscale/level calculations.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- Lu, Can, et al.
(författare)
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Semi Transparent Three-Dimensional Macroporous Quaternary Oxynitride Photoanodes for Photoelectrochemical Water Oxidation
- 2022
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 34:15, s. 6902-6911
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Tidskriftsartikel (refereegranskat)abstract
- Semi transparent three-dimensional macroporous (3DM) photoanodes based on quaternary oxynitrides have the potential to simultaneously realize superior light harvesting and efficient charge transfer in a tandem photoelectrochemical (PEC) cell. A 3DM CaTaO2N photoanode was prepared for the first time on a GaN/Al2O3 substrate via a chemical route, and it exhibits a high transmittance of > 60% in the wide solar spectrum and a photoresponse onset at -0.3 V versus the reversible hydrogen electrode (V-RHE) under simulated solar illumination. In particular, a plateau photocurrent density of 0.21 mA cm(-2) was achieved at a low potential of 0.4 V-RHE , which was 1.6-fold and more than 50-fold higher than a two-dimensional macroporous (2DM) CaTaO2N/GaN/Al2O3 photoanode and a conventional particle-based CaTaO2N/GaN/Al2O3 photoanode, respectively. The bicontinuous, interconnected pore structure within this 3DM film can improve charge carrier separation and collection by reducing the average diffusion distance for minority carriers toward the electrolyte. Optical measurements and simulations verified the enhanced sunlight harvesting in the 3DM photoanode, which was ascribed to the concentrated distribution of the electric field and multiple scattering. This study provides guidance for future synthesis of highly efficient semitransparent 3DM quaternary oxynitride-based photoanodes for a tandem PEC device.
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| 11. |
- Lu, Can, et al.
(författare)
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Sensibilization of p-NiO with ZnSe/CdS and CdS/ZnSe quantum dots for photoelectrochemical water reduction
- 2021
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 13:2, s. 869-877
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Tidskriftsartikel (refereegranskat)abstract
- Core/shell quantum dots (QDs) paired with semiconductor photocathodes for water reduction have rarely been implemented so far. We demonstrate the integration of ZnSe/CdS and CdS/ZnSe QDs with porous p-type NiO photocathodes for water reduction. The QDs demonstrate appreciable enhancement in water-reduction efficiency, as compared with the bare NiO. Despite their different structure, both QDs generate comparable photocurrent enhancement, yielding a 3.8- and 3.2-fold improvement for the ZnSe/CdS@NiO and CdS/ZnSe@NiO system, respectively. Unraveling the carrier kinetics at the interface of these hybrid photocathodes is therefore critical for the development of efficient photoelectrochemical (PEC) proton reduction. In addition to examining the carrier dynamics by the Mott–Schottky technique and electrochemical impedance spectroscopy (EIS), we performed theoretical modelling for the distribution density of the carriers with respect to electron and hole wave functions. The electrons are found to be delocalized through the whole shell and can directly actuate the PEC-related process in the ZnSe/CdS QDs. The holes as the more localized carriers in the core have to tunnel through the shell before injecting into the hole transport layer (NiO). Our results emphasize the role of interfacial effects in core/shell QDs-based multi-heterojunction photocathodes.
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| 12. |
- Ma, Zili, et al.
(författare)
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CeTiO2N oxynitride perovskite : paramagnetic N-14 MAS NMR without paramagnetic shifts
- 2021
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Ingår i: Zeitschrift für Naturforschung. B, A journal of chemical sciences. - : Walter de Gruyter GmbH. - 0932-0776 .- 1865-7117. ; 76:5, s. 275-280
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Tidskriftsartikel (refereegranskat)abstract
- N-14 magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of diamagnetic LaTiO2N perovskite oxynitride and its paramagnetic counterpart CeTiO2N are presented. The latter, to the best of our knowledge, constitutes the first high-resolution N-14 MAS NMR spectrum collected from a paramagnetic solid material. The unpaired 4f-electrons in CeTiO2N do not induce a paramagnetic N-14 NMR shift. This is remarkable given the direct Ce-N contacts in the structure for which ab initio calculations predict substantial Ce -> N-14 contact shift interaction. The same effect is revealed with N-14 MAS NMR for SrWO2N (unpaired 5d-electrons).
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| 13. |
- Ma, Zili, et al.
(författare)
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Combining Electrocatalysts and Biobased Adsorbents for Sustainable Denitrification
- 2021
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 9:10, s. 3651-3660
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Tidskriftsartikel (refereegranskat)abstract
- Efficient treatment of domestic and industrial wastewater is one of the major challenges of the 21st century. Among the inorganic pollutants, nitrogen species are significant contaminants and the management of the nitrogen cycle is one the most crucial parts of wastewater purification. Herein, we report an integrated method that minimizes the amount of chemicals used, can be empowered by renewable energy, uses renewables materials for ammonia recovery, and is scalable. Complete denitrification of wastewater was achieved by combining electrochemical and adsorption treatment for real wastewater samples from the Stockholm water pilot plant. About 98% of nitrate was selectively converted to ammonia over abundant copper electrocatalysts in the presence of Na2SO4-supporting electrolyte at -0.6 V vs reversible hydrogen electrode (RHE) within 3 h. The valorized nitrate in the form of ammonia could be recovered by means of cheap kraft lignin-SiO2 sorbents to achieve total denitrification. The presented method is economically feasible, scalable, and contributes to sustainable recycling within a circular economy.
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| 14. |
- 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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| 15. |
- Ma, Zili, et al.
(författare)
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Quaternary Core-Shell Oxynitride Nanowire Photoanode Containing a Hole-Extraction Gradient for Photoelectrochemical Water Oxidation
- 2019
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11:21, s. 19077-19086
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Tidskriftsartikel (refereegranskat)abstract
- A nanowire photoanode SrTaO2N, a semiconductor suitable for overall water-splitting with a band gap of 2.3 eV, was coated with functional overlayers to yield a core-shell structure while maintaining its one-dimensional morphology. The nanowires were grown hydrothermally on tantalum, and the perovskite-related oxynitride structure was obtained by nitridation. Three functional overlayers have been deposited on the nanowires to enhance the efficiency of photoelectrochemical (PEC) water oxidation. The deposition of TiOx protects the oxynitride from photocorrosion and suppresses charge-carrier recombination at the surface. Ni(OH)(x) acts a hole-storage layer and decreases the dark-current contribution. This leads to a significantly improved extraction of photogenerated holes to the electrode-electrolyte surface. The photocurrents can be increased by the deposition of a cobalt phosphate (CoPi) layer as a cocatalyst. The heterojunction nanowire photoanode generates a current density of 0.27 mA cm(-2) at 1.23 V vs the reversible hydrogen electrode (RHE) under simulated sunlight (AM 1.5G). Simultaneously, the dark-current contribution, a common problem for oxynitride photoanodes grown on metallic substrates, is almost completely minimized. This is the first report of a quaternary oxynitride nanowire photoanode in core-shell geometry containing functional overlayers for synergetic hole extraction and an electrocatalyst.
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| 16. |
- 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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| 17. |
- Ma, Zili, et al.
(författare)
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Structural Properties of NdTiO2+xN1-x and Its Application as Photoanode
- 2021
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 60:2, s. 919-929
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Tidskriftsartikel (refereegranskat)abstract
- Mixed-anion inorganic compounds offer diverse functionalities as a function of the different physicochemical characteristics of the secondary anion. The quaternary metal oxynitrides, which originate from substituting oxygen anions (O2-) in a parent oxide by nitrogen (N3-), are encouraging candidates for photoelectrochemical (PEC) water splitting because of their suitable and adjustable narrow band gap and relative negative conduction band (CB) edge. Given the known photochemical activity of LaTiO2N, we investigated the paramagnetic counterpart NdTiO2+xN1-x. The electronic structure was explored both experimentally and theoretically at the density functional theory (DFT) level. A band gap (E-g) of 2.17 eV was determined by means of ultraviolet-visible (UV-vis) spectroscopy, and a relative negative flat band potential of -0.33 V vs reversible hydrogen electrode (RHE) was proposed via Mott-Schottky measurements. N-14 solid state nuclear magnetic resonance (NMR) signals from NdTiO2+xN1-x could not be detected, which indicates that NdTiO2+xN1-x is berthollide, in contrast to other structurally related metal oxynitrides. Although the bare particle-based photoanode did not exhibit a noticeable photocurrent, Nb2O5 and CoOx overlayers were deposited to extract holes and activate NdTiO2+xN1-x. Multiple electrochemical methods were employed to understand the key features required for this metal oxynitride to fabricate photoanodes.
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| 18. |
- 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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| 19. |
- 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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| 20. |
- Ren, Peng, et al.
(författare)
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An Atomically Dispersed Mn-Photocatalyst for Generating Hydrogen Peroxide from Seawater via the Water Oxidation Reaction (WOR)
- 2023
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Ingår i: Journal of the American Chemical Society. - 0002-7863 .- 1520-5126. ; 145:30, s. 16584-16596
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have fabricatedan aryl amino-substitutedgraphiticcarbon nitride (g-C3N4) catalyst with atomicallydispersed Mn capable of generating hydrogen peroxide (H2O2) directly from seawater. This new catalyst exhibitedexcellent reactivity, obtaining up to 2230 & mu;M H2O2 in 7 h from alkaline water and up to 1800 & mu;Mfrom seawater under identical conditions. More importantly, the catalystwas quickly recovered for subsequent reuse without appreciable lossin performance. Interestingly, unlike the usual two-electron oxygenreduction reaction pathway, the generation of H2O2 was through a less common two-electron water oxidation reaction(WOR) process in which both the direct and indirect WOR processesoccurred; namely, photoinduced h(+) directly oxidized H2O to H2O2 via a one-step 2e(-) WOR, and photoinduced h(+) first oxidized a hydroxide (OH-) ion to generate a hydroxy radical ((OH)-O-& BULL;), and H2O2 was formed indirectly by thecombination of two (OH)-O-& BULL;. We have characterized thematerial, at the catalytic sites, at the atomic level using electronparamagnetic resonance, X-ray absorption near edge structure, extendedX-ray absorption fine structure, high-resolution transmission electronmicroscopy, X-ray photoelectron spectroscopy, magic-angle spinningsolid-state NMR spectroscopy, and multiscale molecular modeling, combiningclassical reactive molecular dynamics simulations and quantum chemistrycalculations.
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| 21. |
- Rodrigues, Bruno Vinicius Manzolli, et al.
(författare)
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Selective electrochemical recoveries of Cu and Mn from end-of-life Li-ion batteries
- 2023
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Ingår i: Resources, Conservation and Recycling. - 0921-3449 .- 1879-0658. ; 197
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-ion batteries (LIBs) are a tremendous achievement in the current energy storage landscape. However, there is an increasing demand for their implementation due to a variety of applications, such as mobile devices and a growing market of electric vehicles. Hence, the recycling of end-of-life batteries is one of the ways to satisfy the need for manufacturing new ones; however, this is challenging due to the lack of sustainable and efficient methods on a large scale. Electrochemical methods are widely used in the production of metals and alloys, therefore constituting a promising way for the recovery of critical metals present in cathode materials in LIBs. In this work, cathode materials have been collected from used LIBs from different sources and leached altogether with sulphuric acid and hydrogen peroxide. The resulting solution was treated electrochemically by applying a constant potential of-0.5 V for 20 h, which promoted the selective separation of copper and manganese at the cathode and anode sides, respectively. Complete and selective recoveries of Cu and Mn were proved by ICP-OES methods, while the purity of the obtained products was assessed by XRD, oS and SEM-EDS analysis. This investigation presents a great potential for the implementation of an electrochemical treatment to recover valuable metals in pure and ready to reuse form from spent LIBs, which can be easily scaled-up as an alternative to current non-green recovery processes.
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| 22. |
- Rokicińska, Anna, et al.
(författare)
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Impact of Mn addition on catalytic performance of Cu/SiBEA materials in total oxidation of aromatic volatile organic compounds
- 2021
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 546
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Tidskriftsartikel (refereegranskat)abstract
- Dealuminated BEA zeolite (SiBEA) was chosen as a support of metal oxide(s) phase for catalytic combustion of volatile organic compounds (VOCs). Copper and/or manganese oxide(s) were deposited at various Cu/Mn molar ratios. Factors influencing the catalytic activity were found by chosen physicochemical methods, including XRD, XRF, low-temperature N-2 adsorption, FT-IR, UV-Vis-DRS, STEM-EDX, XPS and H-2-TPR. Depending on the chemical composition, CuO, (CuxMn3-x)(1-delta)O-4, Cu-doped Mn3O4 or Mn2O3 was formed as the dominant phase. The active phase particles were located mainly in the interparticle voids of the zeolite support. SiBEA gained Lewis acid sites after the introduction of the metal oxide phase, especially in the case of CuO deposition. The presence of copper in the catalytic system resulted in enhanced reducibility of the active phase, and in a consequence in high catalytic activity in the total oxidation of aromatic VOCs, which proceeds according to the Mars-van Krevelen mechanism. After the introduction of Mn, the co-existence of different valence forms was found due to the redox equilibrium: Cu2+ + Mn3+ = Cu+ + Mn4+. Definitely, the addition of Mn to Cu/SiBEA increased the number of available surface vacancies and had a beneficial effect on the catalytic performance.
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| 23. |
- 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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