| 1. |
- Chen, Zheng, et al.
(author)
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Increased photocurrent of CuWO4 photoanodes by modification with the oxide carbodiimide Sn2O(NCN)
- 2020
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In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:11, s. 3450-3456
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Journal article (peer-reviewed)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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| 2. |
- Chen, Zheng, et al.
(author)
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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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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 59:18, s. 13589-13597
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Journal article (peer-reviewed)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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| 3. |
- Ma, Zili, et al.
(author)
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Structural evolution of CrN nanocube electrocatalysts during nitrogen reduction reaction
- 2020
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In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 12:37, s. 19276-19283
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Journal article (peer-reviewed)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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| 4. |
- Nair, Santhosh S., et al.
(author)
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Converting cellulose nanocrystals into photocatalysts by functionalisation with titanium dioxide nanorods and gold nanocrystals
- 2020
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 10:61, s. 37374-37381
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Journal article (peer-reviewed)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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| 5. |
- Onwumere, Joy, et al.
(author)
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CelluPhot : Hybrid Cellulose-Bismuth Oxybromide Membrane for Pollutant Removal
- 2020
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In: ACS Applied Materials and Interfaces. - : NLM (Medline). - 1944-8244 .- 1944-8252. ; 12:38, s. 42891-42901
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Journal article (peer-reviewed)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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| 6. |
- Piątek, Jędrzej, et al.
(author)
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Glycine-functionalized silica as sorbent for cobalt(II) and nickel(II) recovery
- 2020
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In: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 530
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Journal article (peer-reviewed)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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| 7. |
- Szewczyk, Ireneusz, et al.
(author)
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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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In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 32:17, s. 7263-7273
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Journal article (peer-reviewed)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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