Electrochemical Catalytic Oxidation Research Articles

Green preparation of self-supporting platinum nanoflower catalyst and its electrocatalytic oxidation performance of methanol

The three-dimensional (3D) self-supporting Pt nanoflower catalyst was prepared by using Pt organic compounds as precursors in a low-temperature molten salt system. The obtained Pt nanoflower nanoparticle can reach 400–500 nm with a face-centered cubic structure, which has the structural characteristics of a loose framework and more exposed active sites. The surfactant-free Pt nanoflower was directly used as methanol electrooxidation reaction (MOR) electrocatalysts without any pretreatment and activated carbon support. The results of electrochemical catalytic oxidation of methanol showed that the Pt nanoflower catalyst exhibit more enhanced electrocatalytic oxidation performance toward methanol compared with the commercial platinum black catalyst. The green and effective method can be developed and expected to enable mass production of fuel cell catalysts.

Nickel-Doped Carbon Dots as an Efficient and Stable Electrocatalyst for Urea Oxidation.

Urea is a typical contaminant present in wastewater which may cause severe environmental problems. Electrochemical catalytic oxidation of urea has emerged as an efficient approach to solve this problem. Nevertheless, the current nickel-based catalysts (e.g., nickel hydroxide/sulfides) feature a high metal content. It not only lowers the utilization efficiency of nickel but also causes secondary pollution to the environment. Here, nickel-doped carbon dots (Ni-CDs) with an excellent and stable catalytic activity for the electrocatalytic urea oxidation reaction (UOR) are reported. Specifically, carbon dots (CDs) with abundant functional groups are synthesized by a one-pot hydrothermal method and then Ni-CDs with a very low metal content (1.1 at%) are prepared. The Ni2+ sites by coordination with carboxylic groups on the CDs provide excellent electrocatalytic activity and excellent durability for the UOR, as demonstrated by an anodic current density of 100mA cm-2 at a potential of 1.38V (vs RHE) and similar experimental results in practical application. To the best of knowledge, this is the first report of CDs-based materials applied for the UOR, which opens an important new area of applicability for CDs as well as broadens the scope of the materials for electrochemical catalysis of urea.

Highly selective detection of adenine and guanine by NH2-MIL-53(Fe)/CS/MXene nanocomposites with excellent electrochemical performance.

Adenine (A) and guanine (G) are mainly found in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) and play a crucial role in genetic information transfer and protein synthesis. In this study, NH2-MIL-53(Fe)/CS/MXene nanocomposites were prepared for detecting guanine and adenine. With high specific surface area, excellent water dispersion, and numerous active sites, MXene (transition metal carbides, nitrides, and carbonitrides) provides a good platform for loading primitive metal-organic frameworks (MOFs). At the same time, the problem of poor conductivity and dispersion of MOFs is solved. The electrochemical catalytic oxidation of adenine and guanine of NH2-MIL-53 (Fe)/CS/MXene nanocomposites was carried out by differential pulse voltammetry (DPV). Operating voltage of DPV: 0.7-0.9 V (vs. Ag/AgCl) for G, 1.0-1.2 V (vs. Ag/AgCl) for A, 0.8 V (vs. Ag/AgCl), and 1.1 V (vs. Ag/AgCl) for G and A. The concentration ranges for detecting A and G were 3-118 μM and 2-120 μM with detection limits of 0.57 μM and 0.17 μM (S/N = 3), respectively. The nanocomposite was used for detecting G and A in herring sperm DNA, and the content of G and A was found to be about 9 and 11 μM; the RSD values were 3.4 and 1.3%, respectively.

Electrocatalytic oxidation of formaldehyde using electrospinning porous zein-based polyimide fibers

In this work, electrode coated with electrospinning porous polyimide fibers were prepared. The fiber is made by electrospinning zein from corn by-products and polyacrylic acid (PAA). The prepared porous fiber film was loaded with copper and prepared as working electrode material.The specific surface area of the porous fiber membrane is 304.6313 m2/g. The Polyimide (PI)-Cu nanoparticle electrochemical sensor was prepared by supporting non-noble metal Cu on the porous polyimide for the oxidation of formaldehyde. The prepared electrode can be used to catalyze the oxidation of formaldehyde, and the oxidation peak potential is around −0.41 V. Catalytic oxidation for 300 s at the oxidation peak potential can consume formaldehyde 0.758 × 10−6g, and the coulombic efficiency reaches 74.96%. Electrodes made of cheap metals can quickly remove formaldehyde in solution through electrochemical catalytic oxidation.

Study on electrochemical improvement of flotation reagents for carbon recovery from coal gangue

ABSTRACT A novel collector to improve the collecting capacity of the coal gangue and to reduce the consumption of the medicament was proposed in this paper, which the potassium permanganate is used as a catalyst to carry out electrochemical catalytic oxidation modification on the kerosene. The effects of electrolysis time, electrolytic current density, catalyst dosage, electrolyte concentration, different catalysts and electrodes on the oxidation of the kerosene were investigated, and the compositions and properties of before and after kerosene oxidation employing FTIR and GC-MS. Results showed that the oxidation effect is the best which the acid value of the product is 7.32mgKOH/g when the electrolysis time is 40 minutes, the amount of catalyst is 500 mg/L, and the electrolytic current density is 2000 A/m2. The flotation results showed that the amount of collector could be saved by 200 g/t dosage and the frother can be saved by 80 g/t dosage by using oxidized kerosene as a collector when combustible matter recovery was 20−25% higher than that of common kerosene and clean coal yield was 8−10% higher than that of common kerosene. The FTIR and GC-MS analysis of the product revealed that some carbonyl compounds and unsaturated hydrocarbons are formed in the product after electrochemical treatment of kerosene, which enhances the collection performance of kerosene. At the same time, alcohol, ether, and ester-creating in the product make the product has been specific foaming performance. This work provides a new reagent for coal gangue carbon recovery.

Electrochemical enhancement of high-efficiency wet removal of mercury from flue gas

Electrochemical wet absorption composite system has an excellent potential to remove Hg0 from flue gas. In this study, ruthenium iridium titanium platinum quaternary composite electrode is used as an anode and titanium electrode is used as the cathode, and KI/I2 absorption solution is introduced into the electrocatalysis system as an electrolyte to form KI/I2 electrochemical catalytic oxidation system. The removal rate of Hg0 in flue gas can be increased to 92.3%. The effects of electrolytic voltage, current, Pt content, I2 concentration, and the ratio of KI/I2 on the removal of Hg0 were discussed. The possible free radicals in the electrochemical cathode, anode, and solution were characterized and tested by XRD, SEM, UV-Vis (detection of H2O2, ·OH, O3), and FTIR (detection of IO3-). Combined with experimental data and theoretical derivation, the mechanism of Hg0 removal from flue gas by electrochemical catalytic oxidation alloy formation wet absorption combined process was studied. The results show that the combined process, which is a promising technology can not only improve the removal efficiency of Hg0, but also realize the resource recovery of Hg0 and I2, and provide a feasibility study for the subsequent regeneration of KI/I2 absorption solution.

Facilely Prepared Cl-Doped Graphene as an Efficient Anode for the Electrochemical Catalytic Degradation of Acetaminophen.

The application of electrochemical catalytic oxidation in wastewater treatment with powerful Cldoped graphene as an anode has been discussed as a novel approach to degrade acetaminophen effectively. The characteristics of Cl-doped graphene that were related to Cl loading content and microscopic morphology were analyzed by using several instruments, and the defects created by Cl doping were identified. Quenching experiments and electron paramagnetic resonance detection were proposed to clarify the mechanism underlying the production of active free radicals by Cldopedgraphene. The degradation results indicated that efficiency increased with the percentage of Cl atoms doped into the graphene. The best degradation efficiency of acetaminophen could reach 98% when Cl-GN-12 was used. In the process of electrocatalytic oxidation, O•-₂, and active chlorine, as the main active species, persistently attacked acetaminophen into open-ring intermediates, such as 4-chlororesorcinol, and finally into CO₂ and H²O.

Electrocatalytic degradation of acetaminophen by fluorine-doped graphene oxide: Efficiency and mechanism under constant current and pulse current supply

Doping graphene with fluorine atoms could increase the capacitance of graphene and promote the migration of ions and electrons, thereby increasing electrocatalytic activity. For energy conservation and environmental protection, fluorine-doped graphene oxide was made by an effective solvothermal method and then used as a cathode for acetaminophen (APAP) degradation under constant current and pulse current supply. Unexpectedly, the removal rate of APAP was the same under constant current and pulse current supply within 120 min. To clarify the underlying mechanism under constant current and pulse current supply, various active species generated during the reaction were analyzed. It was found that the different functional active species contributed to the efficiency under constant current and pulse current supply. O2•− and chloride reactive species were favorably generated during constant current supply and oxidized APAP, whereas •OH played a critical role in APAP oxidation without current supply. Two possible routes for APAP degradation are proposed under constant current and pulsed current supply. This research first uses the synergic effect of the electron storage capacity and the electrocatalytic capability of fluorine-doped graphene oxide for pollution degradation, and deepens the understanding of fluorine doping for the electrochemical catalytic oxidation of APAP.

Sustainable recovery of high-saline papermaking wastewater: Optimized separation for salts and organics via membrane-hybrid process

In this work, a novel zero liquid discharge technology combining of electrodialysis (ED), electrochemical catalytic oxidation (ECO), reserve osmosis (RO) and bipolar membrane electrodialysis (BMED) was developed for sustainable recovery of high-saline papermaking wastewater. The effect of membrane type, volume ratio, membrane fouling and voltage were investigated in ED process; subsequently parameter such as electrolyte conductivity was studied in ECO process. The FKB/FAB stack shows good separation performance for the salts and organics, allowing a relatively high COD rejection of 97.80%. Meanwhile, membrane fouling was investigated through a comparison between virgin and fouled membranes. To achieve a high-saline solution with low organics, a second-stage ED process was applied. The concentration factor was increased to 1.799 with a COD rejection of 96.54% at voltage of 12 V. Simultaneously, the ECO process exhibited superior COD removal of 94.99% at the electrolyte conductivity of 4 mS/cm. Through the application of BMED at Vf:Vb:Va (volume ratio of feed, base and acid solution) of 4:1:1, the final acid and base content could approach a high value of 12.30 wt% and 10.60 wt%, respectively. Therefore, this hybrid ED-ECO-RO-BMED combined process demonstrates a strongly technical applicability for sustainable resource recovery from high-saline papermaking wastewater.

Experimental Study on Electro Chemical Catalytic Oxidation Desulfurization of High Sulfur Coal Based on Computer

Coal and other fossil energy has a greater pollution, especially in the process of its combustion will bring a variety of environmental pollution problems, such as sulfur dioxide combustion, which produces more serious air pollution. Therefore, in order to reduce coal pollution, it is necessary to carry out desulfurization treatment before coal combustion. There are many shortcomings and problems in the traditional coal desulfurization methods, mainly in secondary pollution and harsh operating environment. As a mild desulfurization and purification technology, the research value of Electrochemical Catalytic Oxidation Desulfurization (ECOD) is highlighted. Based on this, this paper first analyses the process flow and desulfurization mechanism of high sulfur coal Electrocatalytic Oxidation Desulfurization (EOD) technology, and then studies the ECOD technology of high sulfur coal, and verifies the influencing factors of ECOD of high sulfur coal.

Nano-graphene-platelet/Brilliant-green composite coated carbon paste electrode interface for electrocatalytic oxidation of flavanone Hesperidin

We have developed a nanodevice with the aid of adsorption strategy. The key factor being the extensive π-π interactions between sp2 carbons of nano-Graphene-platelets (nGp) and π-e- of cationic Brilliant green (Bg) at the electrode surface, that synergistically promoted Hesperidin (HES) oxidation. From our observations, electrochemical catalytic oxidation of HES significantly magnified on nGp-Bg/Modified carbon paste electrode (nGp-Bg/MCPE), under optimized experimental conditions, such as the volume of composite cast-coated, cationic active sites in the nGp-Bg film, and the pH of the buffer. Surface morphology was characterized using Field Emission Scanning Electron Microscopy (FESEM) and Electron Diffraction X-ray (EDX). Nyquist plots revealed the least charge transfer resistance at nGp-Bg/MCPE compared to other control electrodes. Further, at physiological pH, HES displayed an irreversible electrochemical charge transfer at nGp-Bg/MCPE. The cationic Bg moieties on nGp-Bg/MCPE portrayed a great affinity towards deprotonated HES and its accumulation on the electrode surface. Interactions between aromatic rings in nGp-Bg structure and HES molecules consequently enhanced total surface coverage concentration by 3.6-fold compared to control electrodes via adsorption-controlled-electron-transfer feature. We have demonstrated that the reaction capability of nGp-Bg/MCPE towards HES quantification via synergistic electrocatalytic effect, with the ability to lower the activation energy and hastened oxidation. Quantification of HES was performed using Differential Pulse Voltammetry (DPV). Gp-Bg/MCPE showed selective mediated oxidation current response with the lowest detection limit of 5.0 × 10−8 M in two linear ranges. We have successfully validated trace analysis of HES in fortified fruit juice samples, also extendable to various practical applications. Therefore, the present work has established simplicity in the principle of the novel approach in the development of an ultrasensitive voltammetric sensor for HES.

Magnetic field coupling microfluidic synthesis of Fe2Pt/C nanocatalysts for enhanced electrochemical catalytic oxidation of alcohol

The influence of magnetic field (MF) on electrochemical catalytic properties of carbon supported Fe2Pt nanocatalysts is investigated. Nanocatalysts are produced through an external MF coupled microfluidic process. X-ray diffraction (XRD) measurements show that Fe2Pt nanocrystals (NCs) with larger sizes are synthesized when an external MF of 1.4 T is applied. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) characterizations confirm that more Pt2+ reduces to Pt0 and NCs grow larger under magnetic fields (MFs) than those without MFs. The increased coercivity indicates that more surface unpaired electrons are present and the surface spin configuration changes under MFs. NCs synthesized under MFs show better catalytic performance in alcohol electrochemical catalytic oxidation reactions compared to samples synthesized without MFs. The mass activities significantly increase by 1.10 and 1.24 times and the specific activity increases up to 1.11 and 1.26 times for methanol and ethanol oxidation, respectively, compared to those without MFs.

Electrochemical synthesis of multilayered PEDOT/PEDOT-SH/Au nanocomposites for electrochemical sensing of nitrite

A multilayered film of poly(3,4-ethylenedioxythiophene)/poly(thiomethyl 3,4- ethylenedioxythiophene)/gold nanoparticle (PEDOT/PEDOT-SH/Au) nanocomposites was successfully synthesized on indium tin oxide (ITO) and glassy carbon electrode (GCE) via an electrochemical technique. The structure and morphology of the composite was characterized by FT-IR, UV-vis, EDS, XPS, and SEM analyses. The prepared multilayered PEDOT/PEDOT-SH/Au nanocomposite was used for the electrochemical catalytic oxidation of nitrite by amperometry. The results showed that the microstructures of PEDOT/PEDOT-SH/Au nanocomposites are not strongly dependent on the substrate. Fibrous PEDOT as hard template absorbed EDOT-SH on it to form porous PEDOT/PEDOT-SH. Porous structure had the advantages of large specific surface area and high porosity for nitrite ion adsorption. The thiol group in PEDOT/PEDOT-SH stabilized Au nanoparticles (NPs) effectively through Au-S bond and allowed Au NPs to have high dispersion and excellent electrocatalytic activity. The PEDOT/PEDOT-SH/Au composite prepared on GCE had a good performance in its electrochemical response to nitrite ions. PEDOT/PEDOT-SH/Au/GCE displayed a low oxidation potential (0.74V), a fast response time (< 3s), a low detection limit (0.051μM), two linear ranges (0.15-1mM and 1-16mM), good sensitivity (0.301μAμM-1cm-2 and 0.133μAμM-1cm-2) with good reproducibility, stability, and selectivity. Graphical abstract Schematic representation of the preparation process of the nitrite ion electrochemical sensor.

Removal of Gaseous Elemental Mercury in a Diffusion Electrochemical Reactor Based on a Three-Dimensional Electrode.

A novel three dimensional electrochemical reactor with nickel foam and carbon paper used as the anode and stainless steel mesh used as the cathodewas studied in this research. Oxidation mercury removal is performed in a self-made diffusion reactor. The influence of the electrolysis voltage, pH, gas flow, and other factors on mercury removal is discussed, as well as the mechanism of anodization mercury removal is explored. The experimental results show that nickel foam has a significant effect on the removal of Hg0, and 80–85% removal can be achieved under optimal conditions. Meanwhile, nickel foam has stable performance at high temperatures (60 °C) and in strong alkaline electrolytes, which also play an effective role in anodized oxidation. Although carbon paper is more stable than nickel foam and less affected by experimental factors, it is sensitive to reaction temperature and can only work in the neutral electrolyte at low temperatures. In contrast, electrochemical catalytic oxidation technology using the nickel foam is more promising for Hg0 removal.

Electrochemical pretreatment of coal gasification wastewater with Bi-doped PbO2 electrode: Preparation of anode, efficiency and mechanism

Coal gasification wastewater (CGW) contains a large amount of toxic pollutants, which seriously affects the subsequent biochemical treatment. In order to investigate the efficiency of electrocatalytic oxidation on pretreatment of CGW, lead dioxide electrodes doped with PEG and Bi were successfully prepared. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were comprehensively used to characterize the lead dioxide electrode and the electrochemical performance was also tested by linear sweep voltammetry curve, cyclic voltammetry curve and AC impedance. Biodegradability and toxicity of CGW were evaluated by dehydrogenase activity and acute toxicity, respectively. Results showed that the doping of PEG and Bi significantly improved the electrochemical performance and catalytic oxidation performance of lead dioxide electrodes. The degradation rate of phenol by Sn–Sb/PbO2 (PEG + Bi) electrode were 1.57 times of that by pure lead dioxide electrode. The removal of TOC and total phenols were 53.2% and 82.7%, respectively at 120 min under 40 mA cm−2 by Sn–Sb/PbO2 (PEG + Bi) electrode. The changes of biodegradability, biological toxicity and by-products were analyzed. Furthermore, 3,5-dimethylphenol was used as characteristic pollutant to study the degradation mechanism of phenolic pollutants in electrocatalytic system. According to the intermediate products detected by GC-MS, possible degradation pathways in electrocatalytic system were proposed.

Sulfur doped-graphene for enhanced acetaminophen degradation via electro-catalytic activation: Efficiency and mechanism

Although graphene exhibited excellent performance, its capability of electrochemical catalytic oxidation would significantly improve by modification via sulfur (S)-doping. However, due to the complicated doping species of heteroatoms, the detailed mechanism was still remained open for discussion. Thus, this first-attempt study tended to decipher such mechanism behind the direct and indirect oxidation by analyzing S species in S-graphene. The density functional theory (DFT) was adopted for reactive center calculation and confirmation of secondary active species, to discuss the degradation pathway. As the experimental and calculation results, the thiophene structure S was more favorable for electron acceptation in direct oxidation. Chloride reactive species, as the most effective secondary functionalities (rather than •OH), were favorably generated on the edge doped S position than thiophene structured S in defects, to further trigger the indirect oxidation. However, the extensive contents of reactive functionalities could act as trap for self-annihilation of chloride reactive species, resulting in poor electrocatalytic degradation of the pollutants. This study deepened the understanding of heteroatoms doping for electrochemical catalytic oxidation.

Cobalt nanoparticles embedded in N-doped carbon on carbon cloth as free-standing electrodes for electrochemically-assisted catalytic oxidation of phenol and overall water splitting

Nowadays, environmental pollution and energy depletion are two important problems. In this work, we report the synthesis of cobalt nanoparticles (Co NPs) embedded in nitrogen doped carbon (NC) on carbon cloth (CC) by a two-step method to obtain Co@NC/CC and the application for both electrochemical assisted catalytic oxidation of phenol and electrochemical water splitting. An ultra-high activity could be obtained for the electrochemical catalytic oxidation of phenol, with the rate constant at 1.340 min−1, much larger than the catalytic oxidation process (0.21 min−1). Moreover, Co@NC/CC exhibits remarkable activities in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Especially, a very early HER overpotential of 118 mV is achieved at 10 mA cm−2 in 1 M KOH. The synergistic effect between Co and NC and the intimate interface are proposed to be the main cause of the enhanced activity. The free-standing and multi-functional Co@NC/CC electrode contains no noble metal, and should have great potential both in wastewater remediation and water splitting.

Nanoporous gold induced vertically standing 2D NiCo bimetal-organic framework nanosheets for non-enzymatic glucose biosensing

Designing new efficient electrocatalysts is of considerable importance for the non-enzymatic electrochemical glucose biosensors development. Herein, novel vertical two-dimensional (2D) NiCo bimetal-organic framework (NiCo-MOF) parallelogrammic nanosheets array is successfully prepared on the surface of nanoporous gold by a bottom-up strategy. Nanopores are essential for directing the vertical growth of 2D-MOF nanosheets and preventing them from stacking to form NiCo-MOF arrays. This vertical allignment feature of nanosheets exposes more accessible active sites and facilates fast mass and charge transport for electrochemical reactions. The strong electron interaction among N, Co, and Ni enhances the electrochemical catalytic oxidation of glucose. 2D NiCo-MOF nanosheets array electrode exhibits high performance for glucose detection with a broad linear ranges of 1 μM to 8 mM, a rapid response time of less than 1 s, a high sensitivity of 0.6844 mA·mM−1 cm−2, and a low detection limit of 0.29 μM. This novel vertical aligned NiCo-MOF nanosheets array is also one kind of promising candidates for multifunctional applications in other fields of energy or catalysis.

In-situ reaction-growth of PtNiX nanocrystals on supports for enhanced electrochemical catalytic oxidation of ethanol via continuous flow microfluidic process

An in-situ composite methodology was first proposed to prepare carbon supported PtNix (X = 1, 3, 1/3) via online reaction, nucleation and growth of nanocrystals (NCs) on carbon support along the microfluidic channel. Uniform dispersed ultra-small PtNiX NCs (1 nm–3 nm) with high surface exposed Pt atoms and enhanced nanocrystal-carbon interface interaction can be constructed. The annealed nanocomposites with a Pt/Ni ratio of 1/3 exhibit a mass catalytic activity of 7.6 times higher than the commercial Pt/C nanocatalysts in the ethanol oxidation reaction. The chronoamperometry measurement indicates that their mass activity still retains 3.6 times of the commercial Pt/C nanocatalysts at 4000 s. Moreover, PtNi3/C nanocatalysts have the highest tolerance to CO poisoning according to CO stripping measurements.

External oxidant-free cross-coupling: electrochemically induced aromatic C-H phosphonation of azoles with dialkyl-H-phosphonates under silver catalysis.

A convenient external oxidant-free method of phosphorylation of azole derivatives (benzo-1,3-azoles, 3-methylindole, 4-methyl-2-acetylthiazole) by using dialkyl-H-phosphonates through the catalytic oxidation of their mixture under electrochemical mild conditions (room temperature, normal pressure) in the presence of silver salts or oxide (1%) is proposed. This method allows us to obtain the desired azole dialkylphosphonates with good yield (up to 75%). The transformations of silver and phosphorus precursors and intermediates using cyclic voltammetry, ESR, and NMR spectroscopy were investigated, and a radical process mechanism was proposed. It has been found that AgP(O)(OEt)2 is oxidized earlier than other components of the reaction mixture with the elimination of a radical. The ESR spectrum of this radical's adduct was obtained in the presence of the radical trap PBN. Ag2+ is out of the catalytic cycle.