| 1. |
- A. da Cruz, Márcia G., et al.
(författare)
-
Solvent-free synthesis of photoluminescent carbon nanoparticles from lignin-derived monomers as feedstock
- 2023
-
Ingår i: Green Chemistry Letters and Reviews. - 1751-8253 .- 1751-7192. ; 16:1
-
Tidskriftsartikel (refereegranskat)abstract
- Photoluminescent carbon nanoparticles (CNPs), such as carbon dots (CDs), have attracted much attention owing to a unique set of properties, like high and tunable fluorescence. In this way, the use of carbon-rich lignin has been demonstrated to be a sustainable approach to producing a broad range of photoluminescent CNPs. However, the valorization of this complex polyphenol is limited when it comes to green and efficient ways of conversion. In addition, the existing solvothermal approaches using lignin often result in CDs with low photoluminescence, while flammable and/or toxic solvents are employed. Here, we depolymerized technical lignins, i.e. kraft and soda, through electroreductive cleavage in two different sustainable media: deep eutectic solvent and levulinic acid. After depolymerization, lignin-derived monomers were generated, with a predominance of aryl ether and phenolic groups, which were further combined with 1,2-Phenylenediamine to produce N-doped CNPs in a solvent-free approach. Photoluminescent CNPs with varied sizes were generated (5–50 nm), which presented a wide photoluminescence emission, from blue to red, depending on solvent polarity. These results demonstrate a feasible and sustainable route for the solvent-free synthesis of photoluminescent CNPs using lignin-derived monomers as carbon source, which may find applications in a wide range of fields.
|
|
| 2. |
- Chen, Jianhong, 1993-
(författare)
-
Biomass-derived nanoscopic catalysts for water treatment : Structure-property relationship investigation
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Green Chemistry has received widespread interest due to its capacity to meet environmental and economic objectives. The Twelve Principles were proposed to better perform Green Chemistry and have become the guideline for solving many environmental issues. Water contamination has become a major global challenge in the 21st century. Millions of people die from diseases caused by drinking contaminated water. Nitrate, metal ions and dye are the most frequent contaminants. Nitrate in drinking water, after ingestion, is reduced to nitrite by the gastrointestinal tract and threatens human health. Dye-polluted water is usually nonbiodegradable and poisonous: the main criticism is that it is harmful to human health and hampers the photosynthesis rate of aquatic life. Metal ions generally lead to biological and physiological complications when they bind to cellular macromolecules. Therefore, efficient and eco-friendly purification technology is pressing to provide solutions for water purification. This thesis is set out to investigate the electro-/photo- catalytical water purification techniques using different catalysts. Efficient nitrate electrochemical reduction was achieved by using NDC materials, and the active sites were determined with the help of a comprehensive solid-state NMR supported by theoretical calculation and DFT calculations. Furthermore, the photochemical dye degradation was performed using cellulose-based hybrid bio-inorganic catalysts. The intentional maintenance of the surface functional groups on cellulose-based materials can promote dye degradation performance and, most importantly, achieve simultaneous removal of heavy metal ions aside from photo dye degradation. Additionally, this thesis proposed two possible synthesis strategies to obtain electro-/photo- catalysts using cellulose-based materials as renewable resources. The Twelve Principles of Green Chemistry guided the optimization of the synthesis route and raw material selectivity. Notably, the low-temperature synthesis of hybrid photocatalysts maintained the surface functional groups and preserved the kinetic mechanism of contaminants' adsorption on bio-substrate. This research is likely to contribute to a deeper understanding of renewable materials with green synthesis methods for catalysts targeting water contamination treatment.
|
|
| 3. |
- Das, Biswanath, et al.
(författare)
-
Bifunctional and regenerable molecular electrode for water electrolysis at neutral pH
- 2023
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 11:25, s. 13331-13340
-
Tidskriftsartikel (refereegranskat)abstract
- The instability of molecular electrodes under oxidative/reductive conditions and insufficient understanding of the metal oxide-based systems have slowed down the progress of H2-based fuels. Efficient regeneration of the electrode's performance after prolonged use is another bottleneck of this research. This work represents the first example of a bifunctional and electrochemically regenerable molecular electrode which can be used for the unperturbed production of H2 from water. Pyridyl linkers with flexible arms (–CH2–CH2–) on modified fluorine-doped carbon cloth (FCC) were used to anchor a highly active ruthenium electrocatalyst [RuII(mcbp)(H2O)2] (1) [mcbp2− = 2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine]. The pyridine unit of the linker replaces one of the water molecules of 1, which resulted in RuPFCC (ruthenium electrocatalyst anchored on –CH2–CH2–pyridine modified FCC), a high-performing electrode for oxygen evolution reaction [OER, overpotential of ∼215 mV] as well as hydrogen evolution reaction (HER, overpotential of ∼330 mV) at pH 7. A current density of ∼8 mA cm−2 at 2.06 V (vs. RHE) and ∼−6 mA cm−2 at −0.84 V (vs. RHE) with only 0.04 wt% loading of ruthenium was obtained. OER turnover of >7.4 × 103 at 1.81 V in 48 h and HER turnover of >3.6 × 103 at −0.79 V in 3 h were calculated. The activity of the OER anode after 48 h use could be electrochemically regenerated to ∼98% of its original activity while it serves as a HE cathode (evolving hydrogen) for 8 h. This electrode design can also be used for developing ultra-stable molecular electrodes with exciting electrochemical regeneration features, for other proton-dependent electrochemical processes.
|
|
| 4. |
- Kaya, Kerem, et al.
(författare)
-
Enhanced Solar CO2 Photoreduction to Formic Acid by Platinum Immobilization on Bipyridine Covalent Triazine Framework with Defects
- 2023
-
Ingår i: Advanced Sustainable Systems. - 2366-7486. ; 7:8
-
Tidskriftsartikel (refereegranskat)abstract
- The immobilization and structural analysis of platinum nanoparticles on a nitrogen-rich, bipyridine-containing covalent triazine framework (bpyCTF) having structural defects are disclosed by taking advantage of 15N solid-state nuclear magnetic resonance measurements at natural 15N isotope abundance and X-ray photoelectron spectroscopic analyses. The photocatalyst (Pt@bpyCTF) with structural defects reduces CO2 to formic acid (FA) at a rate of 152 µmol h−1g−1 and a selectivity higher than 95% over CO and H2 in water under simulated solar light. The presence of amine defects and the immobilization of Pt cause improvement in the photocurrent density and CO2 capture capacity (≈8% by weight) despite the moderate surface area (0.54 cm3 g−1)of the photocatalyst. Theoretical models and density functional theory calculations are employed to investigate the possible CO2 reduction reaction (CO2RR) mechanisms. Considering the exceptional CO2 capture capacity and high FA production using only CO2-bubbled water, this work highlights the great potential of nitrogen-rich CTFs for photocatalyzed CO2RRs under green conditions.
|
|
| 5. |
- Lindenbeck, Lucie, et al.
(författare)
-
MoS2 nanoflower-decorated lignin nanoparticles for superior lubricant properties
- 2023
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; :20
-
Tidskriftsartikel (refereegranskat)abstract
- Lignin has been, for a long time, treated as a low-value waste product. To change this scenario, high-value applications have been recently pursued, e.g., the preparation of hybrid materials with inorganic components. Although hybrid inorganic-based materials can benefit from the reactive lignin phenolic groups at the interface, often responsible for optimizing specific properties, this is still an underexplored field. Here, we present a novel and green material based on the combination of hydroxymethylated lignin nanoparticles (HLNPs) with molybdenum disulfide (MoS2) nanoflowers grown via a hydrothermal route. By bringing together the lubricant performance of MoS2 and the structural stability of biomass-based nanoparticles, a MoS2-HLNPs hybrid is presented as a bio-derived additive for superior tribological performances. While FT-IR analysis confirmed the structural stability of lignin after the hydrothermal growth of MoS2, TEM and SEM micrographs revealed a homogeneous distribution of MoS2 nanoflowers (average size of 400 nm) on the HLNPs (average size of 100 nm). Regarding the tribological tests, considering a pure oil as reference, only HLNPs as bio-derived additives led to a reduction in the wear volume of 18%. However, the hybrid of MoS2-HLNPs led to a considerably higher reduction (71%), pointing out its superior performance. These results open a new window of opportunity for a versatile and yet underexplored field that can pave the way for a new class of biobased lubricants.
|
|
