Direct alcohol fuel cells play a pivotal role in the synthesis of catalysts because of their low cost, high catalytic activity, and long durability in half-cell reactions, which include anode ...(alcohol oxidation) and cathode (oxygen reduction) reactions. However, platinum catalysts suffer from CO tolerance, which affects their stability. The present study focuses on ultrafine Pt nanoparticles stabilized by flowerlike MoS
/N-doped reduced graphene oxide (Pt@MoS
/NrGO) architecture, developed via a facile and cost-competitive approach that was performed through the hydrothermal method followed by the wet-reflux strategy. Fourier transform infrared spectra, X-ray diffraction patterns, Raman spectra, X-ray photoelectron spectra, field-emission scanning electron microscopy, and transmission electron microscopy verified the conversion to Pt@MoS
/NrGO. Pt@MoS
/NrGO was applied as a potential electrocatalyst toward the anode reaction (liquid fuel oxidation) and the cathode reaction (oxygen reduction). In the anode reaction, Pt@MoS
/NrGO showed superior activity toward electro-oxidation of methanol, ethylene glycol, and glycerol with mass activities of 448.0, 158.0, and 147.0 mA/mg
, respectively, approximately 4.14, 2.82, and 3.34 times that of a commercial Pt-C (20%) catalyst. The durability of the Pt@MoS
/NrGO catalyst was tested via 500 potential cycles, demonstrating less than 20% of catalytic activity loss for alcohol fuels. In the cathode reaction, oxygen reduction reaction results showed excellent catalytic activity with higher half-wave potential at 0.895 V versus a reversible hydrogen electrode for Pt@MoS
/NrGO. The durability of the Pt@MoS
/NrGO catalyst was tested via 30 000 potential cycles and showed only 15 mV reduction in the half-wave potential, whereas the Pt@NrGO and Pt-C catalysts experienced a much greater shift (Pt@NrGO, ∼23 mV; Pt-C, ∼20 mV).
Blitzlichtfische suchen nachts nach Nahrung und beleuchten dazu ihre Umgebung mit Hilfe von zwei Leuchtorganen unter den Augen. Darin befinden sich symbiontische Leuchtbakterien, die als Nebenprodukt ...einer Oxidation blau‐grünes Licht aussenden.
Blitzlichtfische suchen nachts nach Nahrung und beleuchten dazu ihre Umgebung mit Hilfe von zwei Leuchtorganen unter den Augen. Darin befinden sich symbiontische Leuchtbakterien, die als Nebenprodukt einer Oxidation blau‐grünes Licht aussenden.
Oxidation chemistry using enzymes is approaching maturity and practical applicability in organic synthesis. Oxidoreductases (enzymes catalysing redox reactions) enable chemists to perform highly ...selective and efficient transformations ranging from simple alcohol oxidations to stereoselective halogenations of non‐activated C−H bonds. For many of these reactions, no “classical” chemical counterpart is known. Hence oxidoreductases open up shorter synthesis routes based on a more direct access to the target products. The generally very mild reaction conditions may also reduce the environmental impact of biocatalytic reactions compared to classical counterparts. In this Review, we critically summarise the most important recent developments in the field of biocatalytic oxidation chemistry and identify the most pressing bottlenecks as well as promising solutions.
Oxidoreductases enable highly selective and efficient transformations, ranging from simple alcohol oxidations to stereoselective halogenations of non‐activated C−H bonds. This Review summarises the most important recent developments in the field of biocatalytic oxidation chemistry and identifies the most pressing bottlenecks as well as promising solutions.
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•The first study focusing on HO and O2− generation in the CaO2/Fe(II) system.•Reactive oxygen species and their generation pathways were proposed.•The strategy enhancing HO generation ...efficiency was developed.•A concept model using CaO2/Fe(II) oxidation technique was addressed.
Calcium peroxide (CaO2) is a stable hydrogen peroxide (H2O2) carrier, and the CaO2/Fe(II) system has been applied for treatment of various pollutants. It is commonly reported in the literature that hydroxyl radical (HO) and superoxide radical anions (O2−) are the two main reactive oxygen species (ROSs) generated in the CaO2/Fe(II) system. However, many of the reported results were deduced from degradation performance rather than specific testing of radical generation. Thus, the specific generation of ROSs and the influence of system conditions on ROSs yield are still unclear. To our knowledge, this is the first study specifically focusing on the generation of HO and O2− in the CaO2/Fe(II) system. Experimental conditions were optimized to investigate the production of HO and O2−. The results showed the influences of CaO2, Fe(II), and solution pH on HO and O2− generation, and the HO generation efficiency was reported for the first time. In addition, the ROSs generation pathways in the CaO2/Fe(II) system were elucidated. A strategy for enhancing HO yield is developed, based on the continuously dosing Fe(II). This proposed strategy has implications for the effective application of in situ chemical oxidation employing CaO2/Fe(II) for groundwater remediation.
In recent years, new advanced oxidation processes based on the electrochemical technology, the so-called electrochemical advanced oxidation processes (EAOPs), have been developed for the prevention ...and remediation of environmental pollution, especially focusing on water streams. These methods are based on the electrochemical generation of a very powerful oxidizing agent, such as the hydroxyl radical (•OH) in solution, which is then able to destroy organics up to their mineralization. EAOPs include heterogeneous processes like anodic oxidation and photoelectrocatalysis methods, in which •OH are generated at the anode surface either electrochemically or photochemically, and homogeneous processes like electro-Fenton, photoelectro-Fenton, and sonoelectrolysis, in which •OH are produced in the bulk solution. This paper presents a general overview of the application of EAOPs on the removal of aqueous organic pollutants, first reviewing the most recent works and then looking to the future. A global perspective on the fundamentals and experimental setups is offered, and laboratory-scale and pilot-scale experiments are examined and discussed.
Dyes are used in various industries as coloring agents. The discharge of dyes, specifically synthetic dyes, in wastewater represents a serious environmental problem and causes public health concerns. ...The implementation of regulations for wastewater discharge has forced research towards either the development of new processes or the improvement of available techniques to attain efficient degradation of dyes. Catalytic oxidation is one of the advanced oxidation processes (AOPs), based on the active radicals produced during the reaction in the presence of a catalyst. This paper reviews the problems of dyes and hydroxyl radical-based oxidation processes, including Fenton's process, non-iron metal catalysts, and the application of thin metal catalyst-coated tubular reactors in detail. In addition, the sulfate radical-based catalytic oxidation technique has also been described. This study also includes the effects of various operating parameters such as pH, temperature, the concentration of the oxidant, the initial concentration of dyes, and reaction time on the catalytic decomposition of dyes. Moreover, this paper analyzes the recent studies on catalytic oxidation processes. From the present study, it can be concluded that catalytic oxidation processes are very active and environmentally friendly methods for dye removal.
•Some newly identified microorganisms for BNR with novel metabolism are reviewed.•Their metabolic pathways and enzymatic reactions in nitrogen cycle are demonstrated.•Their unique advantages over ...canonical nitrifiers/denitrifiers in BNR are revealed.•Their recent development and/or implementation in BNR is discussed and outlook.•The key implications of coupling these microbial communities for BNR are identified.
Biological nitrogen removal (BNR) is a critical process in wastewater treatment. Recently, there have new microbial communities been discovered to be capable of performing BNR with novel metabolic pathways. This review presents the up-to-date status on these microorganisms, including ammonia oxidizing archaea (AOA), complete ammonia oxidation (COMAMMOX) bacteria, anaerobic ammonium oxidation coupled to iron reduction (FEAMMOX) bacteria, anaerobic ammonium oxidation (ANAMMOX) bacteria and denitrifying anaerobic methane oxidation (DAMO) microorganism. Their metabolic pathways and enzymatic reactions in nitrogen cycle are demonstrated. Generally, these novel microbial communities have advantages over canonical nitrifiers or denitrifiers, such as higher substrate affinities, better physicochemical tolerances and/or less greenhouse gas emission. Also, their recent development and/or implementation in BNR is discussed and outlook. Finally, the key implications of coupling these microbial communities for BNR are identified. Overall, this review illustrates novel microbial communities that could provide new possibilities for high-performance and energy-saving nitrogen removal from wastewater.
Electrochemical Hydroboration of Alkynes Aelterman, Maude; Sayes, Morgane; Jubault, Philippe ...
Chemistry : a European journal,
June 4, 2021, Volume:
27, Issue:
32
Journal Article
Peer reviewed
Open access
Herein we reported the electrochemical hydroboration of alkynes by using B2Pin2 as the boron source. This unprecedented reaction manifold was applied to a broad range of alkynes, giving the ...hydroboration products in good to excellent yields without the need of a metal catalyst or a hydride source. This transformation relied on the possible electrochemical oxidation of an in situ formed borate. This anodic oxidation performed in an undivided cell allowed the formation of a putative boryl radical, which reacted on the alkyne.
The electrochemical hydroboration of alkynes by using B2Pin2 as the boron source is reported. This reaction manifold was applied to a broad range of alkynes, giving the hydroboration products in good to excellent yields without the need of a metal catalyst or a hydride source. In addition, the mechanism of this transformation was study.
The electrochemical oxidation of the biorefinery product 5‐(hydroxymethyl)furfural (HMF) to 2,5‐furandicarboxylic acid (FDCA), an important platform chemical for the polymer industry, is receiving ...increasing interest. FDCA‐based polymers such as polyethylene 2,5‐furandicarboxylate (PEF) are sustainable candidates for replacing polyethylene terephthalate (PET). Herein, we report the highly efficient electrocatalytic oxidation of HMF to FDCA, using Ni foam modified with high‐surface‐area nickel boride (NixB) as the electrode. Constant potential electrolysis in combination with HPLC revealed a high faradaic efficiency of close to 100 % towards the production of FDCA with a yield of 98.5 %. Operando electrochemistry coupled to ATR‐IR spectroscopy indicated that HMF is oxidized preferentially via 5‐hydroxymethyl‐2‐furancarboxylic acid rather than via 2,5‐diformylfuran, which is in agreement with HPLC results. This study not only reports a low‐cost active electrocatalyst material for the electrochemical oxidation of HMF to FDCA, but additionally provides insight into the reaction pathway.
Adding value through electrocatalysis: The electrocatalytic oxidation of the biorefinery product 5‐(hydroxymethyl)furfural (HMF) to the prospective platform chemical 2,5‐furandicarboxylic acid (FDCA) over nickel boride (NixB) modified nickel foam in an electrochemical flow reactor proceeds with a very high FDCA yield of 98.5 % at a faradaic efficiency of 100 %. NixB appears to be a very promising catalyst for electrochemical HMF oxidation.
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