Carbon dots with tunable concentrations of trapped anti-oxidant as an efficient metal-free catalyst for electrochemical water oxidation (original) (raw)
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ACS Applied Materials & Interfaces
Achieving green and sustainable chemical processes by replacing organic solvents with water has always been one of the green chemistry goals and a challenging topic for chemists. However, the poor solubility of organic materials is a major limitation to achieving this goal, especially in alcohol oxidation. In this contribution, the development and design of amphiphilic catalysts via abundant, safe, cheaper, and more biocompatible sources have received notable attention. To this purpose, herein, our group successfully synthesized a new multifunctional amphiphilic carbon quantum dot (CQD) composed of 1-aminopropyl-3-methyl-imidazolium chloride ([APMim][Cl]), dodecylamine (DDA), and citric acid (CA)
Materials, 2020
Electrochemical water splitting is known as a potential approach for sustainable energy conversion; it produces H2 fuel by utilizing transition metal-based catalysts. We report a facile synthesis of FeCo2O4@carbon dots (CDs) nanoflowers supported on nickel foam through a hydrothermal technique in the absence of organic solvents and an inert environment. The synthesized material with a judicious choice of CDs shows superior performance in hydrogen and oxygen evolution reactions (HER and OER) compared to the FeCo2O4 electrode alone in alkaline media. For HER, the overpotential of 205 mV was able to produce current densities of up to 10 mA cm−2, whereas an overpotential of 393 mV was needed to obtain a current density of up to 50 mA cm−2 for OER. The synergistic effect between CDs and FeCo2O4 accounts for the excellent electrocatalytic activity, since CDs offer exposed active sites and subsequently promote the electrochemical reaction by enhancing the electron transfer processes. Hence...
Recent Developments in Synthesis and Photocatalytic Applications of Carbon Dots
Catalysts
The tunable photoluminescent and photocatalytic properties of carbon dots (CDs) via chemical surface modification have drawn increased attention to this emerging class of carbon nanomaterials. Herein, we summarize the advances in CD synthesis and modification, with a focus on surface functionalization, element doping, passivation, and nanocomposite formation with metal oxides, transition metal chalcogenides, or graphitic carbon nitrides. The effects of CD size and functionalization on photocatalytic properties are discussed, along with the photocatalytic applications of CDs in energy conversion, water splitting, hydrogen evolution, water treatment, and chemical degradation. In particular, the enzyme-mimetic and photodynamic applications of CDs for bio-related uses are thoroughly reviewed.
Carbon Nanodots as Electrocatalysts towards the Oxygen Reduction Reaction
Electroanalysis
Electrocatalysts perform a key role in increasing efficiency of the oxygen reduction reaction (ORR) and as a result, efforts have been made by the scientific community to develop novel and cheap materials that have the capability to low overpotentials and allow the reaction to occur via a 4 electron pathway, thereby mimicking as close as possible to traditionally utilised platinum. In that context, two different types of carbon nanodots (CNDs) with amide (CND-CONH2) and carboxylic (CND-COOH) surface groups, have herein been fabricated and shown to exhibit excellent electrocatalytic activity towards the ORR in acid and basic media (0.1 M H2SO4 and 0.1 M KOH). CND surface modified carbon screen-printed electrodes allow for a facile electrode modification and enabling the study of the CNDs electrocatalytic activity towards the ORR. CND-COOH modified SPEs are found to exhibit improved ORR peak current and reduced overpotential by 21.9% and 26.3%, respectively compared to bare/unmodified SPEs. Additionally, 424 µg cm-2 CND-COOH modified SPEs in oxygenated 0.1 M KOH are found to facilitate the ORR via a near optimal 4 (3.8) electron ORR pathway. The CNDs also exhibited excellent long-term stability and tolerance with no degradation being observed in the achievable current with the ORR current returning to the baseline level within 100 seconds of exposure to a 1.5 M solution of methanol. In summary, the CND-COOH could be utilised as a cathodic electrode for PEMFCs offering greater stability than a commercial Pt electrode.
Precursor-Dependent Photocatalytic Activity of Carbon Dots
Molecules
This work systematically compares both structural features and photocatalytic performance of a series of graphitic and amorphous carbon dots (CDs) prepared in a bottom-up manner from fructose, glucose, and citric acid. We demonstrate that the carbon source and synthetic procedures diversely affect the structural and optical properties of the CDs, which in turn unpredictably influence their photo electron transfer ability. The latter was evaluated by studying the photo-reduction of methyl viologen. Overall, citric acid-CDs were found to provide the best photocatalytic performance followed by fructose- and glucose-CDs. However, while the graphitization of glucose- and citric acid-CDs favored the photo-reaction, a reverse structure–activity dependence was observed for fructose-CDs due to the formation of a large graphitic-like supramolecular assembly. This study highlights the complexity to design in advance photo-active bio-based carbon nanomaterials.
Journal of the Chinese Chemical Society, 2016
Carbon quantum dot (CQD) nanoparticles are synthesized by one-step electrochemical method, cyclic voltammetry (CV), at different potentials using graphite rods and NaOH/EtOH as electrolyte. The electrochemically manufactured CQD is characterized by Transmission electron microscopy, Ultra violet absorption, X-ray diffraction and Fourier transform infrared spectrometry. The morphology and microstructure methods confirm the formation of high quality CQD. Finally, we design a new gas diffusion electrode (GDE) based on CQD pasted on carbon paper for the oxygen reduction reaction at cathode side as methanol tolerance in direct methanol fuel cell and compared it with standard Pt-C catalysts using cyclic voltammetry and linear sweep voltammetry. The ORR results in presence of methanol indicate that the GDE prepared from CQD exhibits methanol tolerance compared to the GDE prepared from Pt/C (Electrochem).
2021
Cutting-edge technologies are intensifying into new skylines and this remarkable progress has been successfully influenced by the tiny level engineering of carbon dots technology, their syn-thesis advancement and impressive applications in the field of allied sciences. The advances of science and its conjugation with interdisciplinary fields emerged in carbon dots making, their controlled characterization and applications into faster, cheaper as well as more reliable prod-ucts in various scientific domains. Thus, a new era in nanotechnology has developed into carbon dots technology. The understanding of the generation process, control on making processes and selected applications of carbon dots such as energy storage, environmental monitoring, catalysis, contaminates detections and complex environmental forensics, drug delivery, drug targeting and other biomedical applications etc. are among the most promising applications of carbon dots and thus a thrust area of research today. In ...
DEVELOPMENT OF METAL-FREE CARBON DOTS BASED ELECTROCATALYSTS FOR HYDROGEN EVOLUTION REACTION
2022
Hydrogen evolution reaction (HER) is of high priority at present. Existing research has involved the use of noble metals as catalysts for HER, thus putting an urgency to develop low-cost materials to replace them. Carbon dots (CDs) are a type of carbon nanomaterial with excellent potential for applications in catalysis. The main motivation for this research was to produce efficient metal-free carbon based electrocatalysts for HER. CDs were synthesized from oleic acid using bottom-up approach and functionalized with elements influencing their electrochemical kinetics. Optical, imaging, and electrochemical characterization was performed to understand the electrocatalytic performance. Mechanistic insights on the formation of CDs were inferred from the spectroscopic characterization. Likewise imaging data delivered a suitable link between morphology, and the catalytic performance. Electrochemical investigation demonstrated excellent electrocatalytic performance with an overpotential at 0.001 VRHE at a current density of-5 mA cm−2. The performance at this range marks a significant milestone and this thesis project paves way for a sustainable future of low-cost efficient metal-free catalysis.