Enhanced ammonia oxidation on BDD induced by inhibition of oxygen evolution reaction

Electrochemical oxidation of ammonia (NH₃ and NH₄ ⁺ ) on boron-doped diamond (BDD) electrode was studied using differential electrochemical mass-spectrometry (DEMS) and chronoamperometry. Electro-oxidation of ammonia induces inhibition of the oxygen evolution reaction (OER) due to adsorption of the ammonia oxidation products on the BDD surface. The inhibition of the OER enhances ammonia electro-oxidation, which becomes the main reaction. The amino radicals, formed during ammonia oxidation, trigger a reaction chain in which molecular oxygen dissolved in solution is involved in the ammonia electro-oxidation. Nitrogen, nitrous oxide, and nitrogen dioxide were detected as the ammonia oxidation products, with nitrogen being the main gaseous product of the oxidation.     

Hydroxyl radicals electrochemically generated in situ on a boron-doped diamond electrode

The hydroxyl radicals electrochemically generated in situ on a boron-doped diamond (BDD) electrode have been investigated for the first time in different electrolyte media, over the whole pH range between 1 and 11. A more extensive characterisation of BDD electrochemical properties is very important to understand the reactivity of organic compounds towards electrochemical oxidation on the BDD electrode, which is related to their interaction with adsorbed hydroxyl radicals due to water oxidation on the electrode surface. An oxidation peak corresponding to the transfer of one electron and one proton was observed in pH <9 electrolytes, associated with the water discharge process and electrochemical generation of hydroxyl radicals, which can interact and enhance the electro-oxidation of organic compounds. In pH >9 electrolytes the electrochemical generation of hydroxyl radicals was not observed; ammonia buffer electrolyte gave a pH-independent peak corresponding to the ammonia oxidation reaction. Additionally, for most pH values studied, a few small peaks associated with the electrochemical interaction between non-diamond carbon species on the doped diamond electrode surface and the electrolyte were also seen, which suggests that the doped diamond is relatively unreactive, but not completely inert, and the electrogenerated hydroxyl radicals play a role as mediator in the oxidation of organics.     

Synthetic boron-doped carbonado,a new electrode material: synthesis in C–metal–B growth systems aimed at the lowering of the synthesis temperature without loss of electrochemical activity

New electrode material—boron-doped synthetic carbonado (bulk polycrystalline diamond)—was synthesized at high pressures and high temperatures in the C–metal (Co, Ni, or Fe) –B growth systems. The metal borides were used as the growth medium-forming substances for graphite-to-diamond transformation at a temperature of ~?1300 °C and pressure of 8 GPa. For comparison, etalon carbonado-type electrode with nearly limiting concentration of boron in diamond was synthesized by subjecting the mixture of amorphous boron with graphite to much higher temperatures (2200–2500 °C) under the same pressure. Despite the lower content of boron in diamond synthesized in the presence of metal borides, these new boron-doped carbonado electrodes are not inferior to the etalon compact in their electrochemical activity, as judging by the onset potential of anodic chlorine evolution from KCl solution. The presence of metal-containing structural defects in boron-doped diamond matrix is supposed to be responsible for the somewhat enhanced catalytic activity of the electrodes. High-pressure synthesis of bulk metal-modified boron-doped diamond opens a new avenue in the development of superior functional electrode materials.     

碱性介质中 (氢) 氧化铜修饰电极电催化氧化蔗糖

 A stable copper (hydr)oxide-modified electrode was prepared in 0.5 mol/L NaOH solution by cyclic voltammetry in the range of -250 to 1 000 mV. It can be used for electrochemical studies in the range of -250 to 1 000 mV without interfering peaks because there is no oxidation of copper. During an anodic potential sweep, the electro-oxidation of saccharose on Cu occurred by the formation of Cu^III and this reaction also occurred in the early stages of the reversed cycle until it is stopped by the negative potentials. A mechanism based on the electro-chemical generation of Cu^III active sites and their subsequent consumption by saccharose was proposed, and the rate law and kinetic parameters were obtained. The charge transfer resistance from theoretical and impedance studies was used to verify the mechanism. Under chronoamperometry regimes, the reaction followed Cottrellian behavior. The transfer of up to 21 electrons was observed in further investigations of the electro-oxidation of saccharose on a (hydr)oxide Cu rotating disk electrode.     

Removal and sensing of emerging pollutants released from (micro)plastic degradation: Strategies based on boron-doped diamond electrodes

The negative impacts of microplastics on the environment and human health cannot be unnoticed. Several classes of emerging pollutants with endocrine-disrupting properties such as bisphenol A and its analogs, phthalates, among others, have been reported to migrate out of plastics entering the aquatic environment. Thus, this review aims to draw attention to the significant potential of the boron-doped diamond electrode to contribute to the implementation of mitigation actions for microplastic pollutants. The latest studies in the two main fields of the use of the boron-doped diamond electrode, that is, treatment of wastewater by electrochemical oxidation and a as sensor for pollutants monitoring, are herein reviewed and their main findings highlighted.     

Platinum-macrocycle co-catalyst for electro-oxidation of formic acid

In this work, a new promoter, tetrasulfophthalocyanine (FeTSPc), one kind of environmental friendly material, was found to be very effective in both inhibiting self-poisoning and improving the intrinsic catalysis activity, consequently enhancing the electro-oxidation current during the electro-oxidation of formic acid. The cyclic voltammograms test showed that the formic acid oxidation peak current density has been increased about 10 times compared with that of the Pt electrode without FeTSPc. The electrochemical double potential step chronoamperometry measurements revealed that the apparent activity energy decreases from 20.64 kJ mol⁻¹ to 17.38 kJ mol⁻¹ after Pt electrode promoted by FeTSPc. The promoting effect of FeTSPc may be owed to the specific structure and abundant electrons of FeTSPc resulting in both the steric hindrance of the formation of poisoning species (CO) and intrinsic kinetic enhancement. In the single cell test, the performance of DFAFC increased from 80 mW cm⁻² mg⁻¹ (Pt) to 130 mW cm⁻² mg⁻¹ after the anode electrode adsorbed FeTSPc.     

Electrochemically induced mineralization of organics by molecular oxygen on boron-doped diamond electrode

The complete mineralization of organic pollutants present in wastewater is usually achieved via thermally activated oxygen/air. This process occurs at high temperatures and pressures (300 °C, 200 atm) and often gives small amount of acetic acid as a final product. In this work, we demonstrate using acetic acid as a model compound that organic molecules can be activated electrochemically such that they react at room temperature with oxygen, resulting in mineralization of even acetic acid present in 1 M HClO₄ supporting electrolyte. This electrochemically induced activation occurs during anodic polarization of boron-doped diamond electrodes (BDD) in air/oxygen-saturated solutions. The direct evidence for this process was found during electro-oxidation of acetic acid saturated with isotopically labelled ¹⁸O₂ resulting in evolution of C¹⁸O₂ and C¹⁶O¹⁸O. We suggest that the mechanism of activation on BDD is initiated by hydroxyl radicals formed on the electrode surface.     

三氧杂环己烷的电化学特性

研究了三氧杂环己烷在不同浓度、不同温度和不同酸度时于光滑铂电极上的电化学行为, 初步分析了三氧杂环己烷的反应机理.     

Electro-oxidation of dimethyl ether on platinum nanocubes with preferential {1 0 0} surfaces

Platinum nanocubes with preferential {1 0 0} surfaces are synthesized by colloidal method and characterized by TEM image and hydrogen adsorption/desorption process. The mean diameter of Pt nanocubes is ca. 10.5 nm. The hydrogen adsorption/desorption wave shows clearly the <1 0 0> preferential orientation. It is proved that dimethyl ether oxidation on Pt nanocubes exhibits similar features with bulk Pt single crystal electrode. The catalytic activity of Pt nanocubes for DME electro-oxidation is nearly 3× higher than that on commercial available Pt black catalyst. After potential step to 1.2 V, the surfaces of Pt nanocubes are reconstructed and the activity for DME electro-oxidation decreases.     

A review of electrochemical reduction processes to treat oxidized contaminants in water

The purpose of this review is to provide a short overview of electrochemical reduction processes for oxidized contaminants in water. The major parameters affecting the electroreduction mechanisms and the impact of electrode choice are discussed with reference to both inorganic and organic pollutants that are either regulated or emerging (e.g., nonmetal oxyanions, perfluoroalkyl and polyfluoroalkyl substances). To conclude, a discussion is presented on the future directions and challenges that must be addressed to develop these electrochemical reduction processes at a larger, commercialized scale.     

Simultaneous growth of diamond and nanostructured graphite thin films by hot-filament chemical vapor deposition

Diamond and graphite films on silicon wafer were simultaneously synthesized at 850 °C without any additional catalyst. The synthesis was achieved in hot-filament chemical vapor deposition reactor by changing distance among filaments in traditional gas mixture. The inter-wire distance for diamond and graphite deposition was kept 5 and 15 mm, whereas kept constant from the substrate. The Raman spectroscopic analyses show that film deposited at 5 mm is good quality diamond and at 15 mm is nanostructured graphite and respective growths confirm by scanning auger electron microscopy. The scanning electron microscope results exhibit that black soot graphite is composed of needle-like nanostructures, whereas diamond with pyramidal featured structure. Transformation of diamond into graphite mainly attributes lacking in atomic hydrogen. The present study develops new trend in the field of carbon based coatings, where single substrate incorporate dual application can be utilized.     

全氟/多氟化合物分析方法的研究进展

随着全氟和多氟化合物（perfluoroalkyl and polyfluoroalkyl substances,PFASs）被列入《斯德哥尔摩公约》的持久性有机污染物名录,各国对于该类物质的关注逐步升高。该类物质在环境中的广泛检出,使得其环境行为研究不断扩展和加深。目前,针对不同类型PFASs的样品前处理方式与检测方法也在不断发展中,而从中选择最合适的前处理和分析方法是开展PFASs环境科学、管理和污染控制研究的前提。该文针对传统PFASs及其异构体、PFASs前体物和新型PFASs等的样品前处理方法、色谱-质谱分析方法进行归纳总结,认识其现状和问题,并在此基础上对其发展进行了展望。     

Electrochemical behavior of new electrode material: Compact of boron-doped synthetic diamond

Electrochemical properties of new electrode material—compact of boron-doped synthetic diamond—is studied for the first time. Cylindrical samples 3.5–4 mm in diameter and 2.5 mm in height were obtained by thermobaric processing of graphite–boron carbide mixtures in the diamond thermodynamic stability region (at the pressure of 8–9 GPa and temperature of ~2500 K). Their electrode behavior is studied using cyclic voltammetry and electrochemical impedance spectroscopy techniques. The cyclic voltammograms of the compact samples showed that their electrode characteristics are similar to those of traditional thin-film diamond electrodes obtained by the chemical vapor deposition (CVD) technique. In particular, they demonstrate rather wide potential window, low background current in indifferent electrolytes, and good reproducibility. It can be concluded that the diamond compacts practically are not inferior to the thin-film CVD-diamond electrodes and can serve as indicator electrodes, e.g., in electroanalysis. At the same time their compact form may be a convenience in the designing of electrolyzers and other electrochemical devices.     

New catalysts for borohydride electro-oxidation using Rh porphyrins

New borohydride electro-oxidation catalysts for direct borohydride fuel cells were developed. These catalysts use rhodium porphyrins on carbon black. The overpotential for borohydride electro-oxidation is much lower than that for a gold electrode. Hydrogen generation by the hydrolysis of borohydride is suppressed much more with rhodium porphyrin catalysts than with a platinum catalyst. Rh porphyrins oxidized borohydride below 0 V vs. a reversible hydrogen electrode. The measurement of hydrogen generation after electrolysis indicates that the apparent number of electrons transferred in rhodium octaethylporphyrin exceeds 7.     

Photocatalytically-assisted electrochemical degradation of <Emphasis Type="Italic">p</Emphasis>-aminophenol in aqueous solutions using zeolite-supported TiO<Subscript>2</Subscript> catalyst

This paper reports the results of an investigation into enhancement of the electrochemical oxidation of p-aminophenol (4-AP) in an aqueous solution with a boron-doped diamond (BDD) electrode, assisted by photocatalysis using a zeolite-supported TiO₂ (Z-TiO₂) catalyst. The BDD electrode was characterised in 0.1 M Na₂SO₄-supporting electrolyte and the presence of 4-AP by open-circuit potential behaviour (OCP) and cyclic voltammetry (CV). The electrode behaviour was investigated in the dark and following UV irradiation and in the absence/presence of the Z-TiO₂ catalyst. The electro-oxidation process was carried out using chronoamperometry (CA) and multiple-pulsed amperometry (MPA) at the selected potential under potentiostatic conditions. The electrochemical degradation process of 4-AP on the BDD electrode was improved by the application of a pulsed potential, which allowed both in-situ electrochemical cleaning of the electrode and indirect oxidation of 4-AP by oxygen evolution. The application of photocatalysis using Z-TiO₂ in the 4-AP electrochemical degradation exhibited an enhanced effect when the anodic potential was set at +1.25 V vs. Ag/AgCl in the water stability region, close to the oxygen evolution potential.     

Analysis of F-53B,Gen-X,ADONA, and emerging fluoroalkylether substances in environmental and biomonitoring samples: A review

The persistent, bioaccumulative, and toxic properties of certain per- and polyfluoroalkyl substances (PFAS) raise concerns for environmental and human health. This has led to the gradual phase-out from production and commerce of some legacy PFAS. Fluoroalkylether compounds (ether-PFAS) are among the fluorinated alternative chemicals that are beginning to be reported in impacted and background environments. Extensive monitoring activities were conducted since 2015–2019 to bridge knowledge gaps on the environmental fate and effects of ether-PFAS including F-53B (6:2 chlorinated polyfluoroalkyl ether sulfonate [6:2 Cl-PFAES] and 8:2 Cl-PFAES), Gen-X (hexafluoropropylene oxide dimer acid [HFPO-DA]), and ADONA (dodecafluoro-3H-4,8-dioxanonanoate). In recent years, advances in nontarget screening using high-resolution mass spectrometry have revealed the identities of other infrequently monitored ether-PFAS. In this critical review, we provide an up-to-date inventory of the structures of ether-PFAS discovered in the recent literature. Their environmental occurrence, fate, and effects are discussed on a comparative perspective with some legacy PFAS such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). Information on the methods employed for the quantitative and semi-quantitative analysis of ether-PFAS is also provided, including sample preparation and mass spectrometry analysis, analytical performance, and limitations. In particular, the compiled database of MS/MS fragment ions (n = 111) can be useful in spectrum interpretation of novel ether-PFAS. The concluding remarks open on possible research avenues and the challenges that remain to be addressed.     

Electrochemical detection of DNA damage induced by in situ generated bisphenol A radicals through electro-oxidation

A glassy carbon electrode was modified with dsDNA and a nanocomposite composed of multi-walled carbon nanotubes and chitosan (MWNT-chit). The electrode was applied to the electrochemical detection of DNA damage as induced by in situ generated bisphenol A (BPA) radicals through electro-oxidation. The modified electrode was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The results indicate that MWNT-chit nanocomposite represents a viable platform for the immobilization of DNA that effectively promotes electron transfer between DNA and the electrode. The mode of interaction between DNA and BPA was investigated by differential pulse voltammetry and UV-vis spectrophotometry, indicating that the dominant interaction is intercalation. In order to explore the mechanism of damage caused by BPA radicals, the electro-oxidation of BPA at the modified glass electrode was investigated. Based on the signal for guanine without any other external indicator, DNA damage was investigated through the electro-oxidation of BPA.     

The impact of water concentration on the catalytic oxidation of ethanol on platinum electrode in concentrated phosphoric acid

The electro-oxidation of ethanol on platinum in phosphoric acid opens the door to promote the oxidation reaction at higher temperatures. However, the effect of the presence of water is not well understood. In this work, the electro-oxidation of ethanol on platinum was studied in concentrated phosphoric acid containing different concentrations of water at room temperature. The results show that effect of bulk water on the rate electro-oxidation is highest at 0.60 V and decreases for increasing potentials. This was suggested as due to the increasing formation of oxygenated species on the electrode surface with potential, which in turn is more efficient than the increase of water content in the electrolyte. Altogether, these results were interpreted as an evidence of a Langmuir–Hinshelwood step involving oxygenated species as one of the adsorbed partners.     

Electropolymerizing polyaniline on undoped 100 nm diamond powder and its electrochemical characteristics

Conductive polyaniline (PANI) was electropolymerized on undoped 100 nm diamond powders in sulphuric acid solution containing aniline to improve the conductivity and the electrochemistry of the nano- or submicro-scaled diamond particles. Cyclic voltammetry (CV) experiment was carried out at an upper potential of 1.1 V in initial sweeps and a potential range of ?0.2–0.9 V for the growth of PANI on a diamond powder electrode. Field emission-scanning electron microscope (FESEM) result reveals that the diamond particles were well coated by PANI films with globular or fibroid surface morphology. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were employed to investigate the electrochemical properties of the PANI/diamond composite electrode. It presents lower resistance and better capacitance than the pristine diamond powder.     

碳纳米管负载纳米铂修饰电极及电催化氧化H2O2的研究

采用化学气相沉积法在碳纳米管(CNT)上负载Pt纳米颗粒,并制备了CNT-Pt修饰玻碳电极(CNT-Pt/GCE).研究了该修饰电极在磷酸缓冲液中对H2O2的电催化氧化作用以及实验条件的影响.计算了H2O2在CNT-Pt/GCE上的电极反应速率常数.结果表明,CNT-Pt/GCE对H2O2的电化学氧化具有良好的催化作用,电极反应速率常数比铂电极高约2.65倍.初步探讨了电催化氧化机理,为酶电化学传感器的研制提供了一条新的途径.