| 1. |
- 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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| 2. |
- A. da Cruz, Márcia G., et al.
(författare)
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Electrochemical Depolymerization of Lignin in a Biomass-based Solvent
- 2022
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 15:15
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Tidskriftsartikel (refereegranskat)abstract
- Breaking down lignin into smaller units is the key to generate high value-added products. Nevertheless, dissolving this complex plant polyphenol in an environment-friendly way is often a challenge. Levulinic acid, which is formed during the hydrothermal processing of lignocellulosic biomass, has been shown to efficiently dissolve lignin. Herein, levulinic acid was evaluated as a medium for the reductive electrochemical depolymerization of the lignin macromolecule. Copper was chosen as the electrocatalyst due to the economic feasibility and low activity towards the hydrogen evolution reaction. After depolymerization, high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy revealed lignin-derived monomers and dimers. A predominance of aryl ether and phenolic groups was observed. Depolymerized lignin was further evaluated as an anti-corrosion coating, revealing enhancements on the electrochemical stability of the metal. Via a simple depolymerization process of biomass waste in a biomass-based solvent, a straightforward approach to produce high value-added compounds or tailored biobased materials was demonstrated.
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| 3. |
- Bilgic, Mehmet B., et al.
(författare)
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An unusual zig-zag 2D copper(i) coordination polymer as an outstanding catalyst for azide–alkyne “click” chemistry at room temperature
- 2022
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:46, s. 17543-17546
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Tidskriftsartikel (refereegranskat)abstract
- A straightforward method for the synthesis of a two-dimensional (2D) new copper(I) coordination polymer, namely Cu(bzpdc), containing the ligand benzophenone 4,4′-dicarboxylate, and its effective use as catalyst for the azide–alkyne click chemistry at room temperature is reported. Zig-zag formation caused by cuprophilic interactions resulted in an unprecedented crystal structure with a very high copper content (45.5% by weight). The catalyst was stable up until 300 °C and tolerant to various solvents, including water. Cu(bzpdc) showed excellent catalytic activity for click reactions of several organic azides and alkynes having different functional groups at room temperature and is comparable to its homogenous analogues. The recyclability of Cu(bzpdc) was also tested and proven to be effective.
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| 4. |
- Das, Biswanath, et al.
(författare)
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Cobalt Electrocatalyst on Fluorine Doped Carbon Cloth – a Robust and Partially Regenerable Anode for Water Oxidation
- 2022
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Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 14:18
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Tidskriftsartikel (refereegranskat)abstract
- The low stability of the electrocatalysts at water oxidation (WO) conditions and the use of expensive noble metals have obstructed large-scale H2 production from water. Herein, we report the electrocatalytic WO activity of a cobalt-containing, water-soluble molecular WO electrocatalyst [CoII(mcbp)(OH2)] (1) [mcbp2−=2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine] in homogeneous conditions (overpotential of 510 mV at pH 7 phosphate buffer) and after anchoring it on pyridine-modified fluorine-doped carbon cloth (PFCC). The formation of cobalt phosphate was identified only after 4 h continuous oxygen evolution in homogeneous conditions. Interestingly, a significant enhancement of the stability and WO activity (current density of 5.4 mA/cm2 at 1.75 V) was observed for 1 after anchoring onto PFCC, resulting in a turnover (TO) of >3.6×103 and average TOF of 0.05 s−1 at 1.55 V (pH 7) over 20 h. A total TO of >21×103 over 8 days was calculated. The electrode allowed regeneration of∼ 85 % of the WO activity electrochemically after 36 h of continuous oxygen evolution.
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| 5. |
- 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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| 6. |
- Jin, Cheng, et al.
(författare)
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Low-Cost mmWave Metallic Waveguide Based on Multilayer Integrated Vertical-EBG Structure and its Application to Slot Array Antenna Design
- 2022
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 70:3, s. 2205-2213
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Tidskriftsartikel (refereegranskat)abstract
- A novel methodology to create metallic waveguides with multilayer integrated vertical-electromagnetic bandgap (EBG) structure is proposed in this article, and the structure realizes low-cost millimeter-wave (mmWave) slot array antennas. A multilayer stack of easy-to-process thin metallic etching plates is introduced to design mmWave waveguide using compression fit instead of diffusion bonding and welding assembly process. The electromagnetic (EM) wave leakage from the gaps between the metallic plates is suppressed using the vertical-EBG structure and antiphasing feeding. The dispersion diagrams of the vertical-EBG unit cell are investigated to illustrate the suppression of leakage. Another leakage wave intercepting methodology is adopted by antiphase feeding to prevent leakage wave from the adjacent slot subarrays. Finally, two examples of 2 $\times $ 8 and 8 $\times $ 8 slot array antennas are presented to verify our design concept. The measured impedance bandwidths of the two antennas are 77.1-84.6 GHz (9.3%) and 78.6-84.9 GHz (7.7%). In addition, the 3 dB broadside gain bandwidths are 73.1-85.3 GHz (15.1%) and 76.8-84.4 GHz (9.4%). The results show the aperture efficiencies up to 56.4%.
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| 7. |
- 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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