Integrated system of electro-catalytic oxidation and microbial fuel cells for the treatment of recalcitrant wastewater

The emission of recalcitrant wastewater poses serious threats to the environment. In this study, an integrated approach combining electrocatalytic oxidation (EC) for pretreatment and microbial fuel cells (MFC) for thorough pollutant degradation is proposed to ensure efficient degradation of target substances, with low energy input and enhanced bioavailability of refractory organics. When phenol was used as the pollutant, an initial concentration of 2000 mg/L phenol solution underwent EC treatment under constant current-exponential attenuation power supply mode, resulting in a COD removal rate of 54.53%, and a phenol degradation rate of 99.83%. Intermediate products such as hydroquinone and para-diphenol were detected in the solution. After subsequent MFC treatment, only minor amounts of para-diphenol were left, and the degradation rate of phenol and its intermediate products reached 100%, with an output power density of 110.4 mW m-2. When coal chemical wastewater was used as the pollutant, further examination of the EC-MFC system performance showed a COD removal rate of 49.23% in the EC section, and a 76.21% COD removal rate in the MFC section, with an output power density of 181.5 mW m-2. Microbiological analysis revealed typical electrogenic bacteria (such as Pseudomonas and Geobacter), and specific degrading functional bacteria (such as Stenotrophomonas, Delftia, and Brevundimonas). The dominant microbial communities and their proportions adapted to environmental changes in response to the variation of carbon sources.

Selective electrocatalytic transformation of highly toxic phenols in wastewater to para-benzoquinone at ambient conditions

The selective transformation of organics from wastewater to value-added chemicals is considered an upcycling process beneficial for carbon neutrality. Herein, we present an innovative electrocatalytic oxidation (ECO) system aimed at achieving the selective conversion of phenols in wastewater to para-benzoquinone (p-BQ), a valuable chemical widely utilized in the manufacturing and chemical industries. Notably, 96.4% of phenol abatement and 78.9% of p-BQ yield are synchronously obtained over a preferred carbon cloth-supported ruthenium nanoparticles (Ru/C) anode. Such unprecedented results stem from the weak Ru-O bond between the Ru active sites and generated p-BQ, which facilitates the desorption of p-BQ from the anode surface. This property not only prevents the excessive oxidation of the generated p-BQ but also reinstates the Ru active sites essential for the rapid ECO of phenol. Furthermore, this ECO system operates at ambient conditions and obviates the need for potent chemical oxidants, establishing a sustainable avenue for p-BQ production. Importantly, the system efficacy can be adaptable in actual phenol-containing coking wastewater, highlighting its potential practical application prospect. As a proof of concept, we construct an electrified Ru/C membrane for ECO of phenol, attaining phenol removal of 95.8% coupled with p-BQ selectivity of 73.1%, which demonstrates the feasibility of the ECO system in a scalable flow-through operation mode. This work provides a promising ECO strategy for realizing both phenols removal and valuable organics recovery from phenolic wastewater.

Mechanistic investigation of the electricity and gallic acid synergistically accelerated Fe(III)/Fe(II) cycle for the degradation of carbamazepine

This study investigated the application of a natural plant polyphenol, gallic acid (GA) to form complex with iron to promote the redox cycle of Fe(III)/Fe(II) under neutral initial pH conditions in the electrochemical (EC) system for activation of peroxymonosulfate (PMS) to efficiently degrade carbamazepine (CBZ). Results demonstrated that the synergistic effects of GA and EC significantly improved the removal efficiency, and the EC/GA/Fe(III)/PMS system effectively removed 100% of CBZ within a wide initial pH range of 3.0-7.0. The optimum stoichiometric ratio of GA to Fe(III) was found as 2:1. Investigations including quenching experiment, chemical probe analysis, and electron paramagnetic resonance (EPR) analysis were conducted to identify the primary reaction radicals as •OH, SO4•-, along with the 1O2 and Fe(IV). In the EC/GA/Fe(III)/PMS system, the synergistic effect of GA and electrochemistry led to a remarkable enhancement in the generation of •OH. Furthermore, the complexation reduction mechanism of GA and Fe(III) was proposed based on experimental and instrumental analyses, which demonstrated that the semi-quinone products of GA were the main substances promoting the Fe(III)/Fe(II) cycle. Mass spectrometry results showed that CBZ generated 27 byproducts during degradation, with formic acid as the main product of GA. The degradation efficiency of the EC/GA/Fe(III)/PMS system remained stable and excellent, exhibiting remarkable performance in the presence of various inorganic anions, including Cl- and NO3-, as well as naturally occurring organic compounds such as fulvic acid (FA). Overall results indicated that the EC/GA/Fe(III)/PMS system can be applied to effectively treat practical wastewater treatment without requirement of pH adjustment.

Interfacial coupling effect promotes selective electrocatalytic oxidation of 5-hydroxymethylfurfural into the value-added products under neutral conditions

Owing to the sluggish reaction kinetics, it is a promising yet challenging task to achieve the adequate electricity-driven catalytic oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) in neutral conditions. Herein, we have prepared an elelctrocatalyst with interfacial coupling effect through in-situ growth of Cu phthalocyanine (CuPc) on Co3O4 spinel (Co3O4/CuPc), which constructs an effective electrocatalytic system of HMF oxidation with overall oxidation value-added products yield and total Faraday efficiency up to 80% and 70%, respectively. The interfacial coupling effect between CuPc and Co3O4 spinel improve catalytic activity by effectively boosting the interfacial charge transfer and reducing the formation energy of key *C6H3O4 in the catalytic pathway according to the in situ Raman spectroscopy and DFT simulation. This work illustrates the significance of interfacial coupling effect for developing highly efficient electrocatalysts applied for neutral system of biomass oxidation.

Flower-like 3D MoS2 microsphere/2D C3N4 nanosheet composite for highly sensitive electrochemical sensing of nitrite

Nitrite pollution poses a serious threat to human health and the environment. In this study, a reliable and selective electrochemical (EC) sensor was developed for the quantitative determination of nitrite by combining flower-like three-dimensional (3D) MoS2 microspheres with two-dimensional (2D) C3N4 nanosheets. Benefiting from the synergistic effects of MoS2 and C3N4, the 3D MoS2/2D C3N4 nanocomposite displayed numerous active sites, a 3D mesoporous structure, high conductivity and excellent catalytic activity. The 3D MoS2/2D C3N4-modified glassy carbon electrode (GCE) exhibited a superior electrocatalytic activity toward nitrite oxidation, with a wider linear detection range (0.1-1100 μM), a lower detection limit (LOD) (0.065 μM, S/N = 3), outstanding stability, remarkable reproducibility and strong selectivity. Furthermore, the nitrite EC sensor was successfully applied to detect actual food and environmental samples involving sausage, pickled vegetables, river water and tap water, thus demonstrating the potential of the prepared 3D MoS2/2D C3N4/GCE for food analysis and environmental monitoring.

Electrocatalytic oxidation of gaseous toluene in an all-solid cell using a foam Ti/Sb-SnO2/β-PbO2 anode

Mineralization of benzene, toluene, and xylene (BTX) with high efficiency at room temperature is still a challenge for the purification of indoor air. In this work, a foam Ti/Sb-SnO2/β-PbO2 anode catalyst was prepared for electrocatalytically oxidizing gaseous toluene in an all-solid cell at ambient temperature. The complex Ti/Sb-SnO2/β-PbO2 anode, which was prepared by sequentially deposing Sb-SnO2 and β-PbO2 on a foam Ti substrate, shows high electrocatalytic oxidation efficiency of toluene (80%) at 7 hr of reaction and high CO2 selectivity (94.9%) under an optimized condition, i.e., a cell voltage of 2.0 V, relative humidity of 60% and a flow rate of 100 mL/min. The better catalytic performance can be ascribed to the high production rate of ⋅OH radicals from discharging adsorbed water and the inhibition of oxygen evolution on the surface of foam Ti/Sb-SnO2/β-PbO2 anode when compared with the foam Ti/Sb-SnO2 anode. Our results demonstrate that prepared complex electrodes can be potentially used for electrocatalytic removal of gaseous toluene at room temperature with a good performance.

Rapid synthesis of Palladium-Platinum-Nickel ultrathin porous nanosheets with high catalytic performance for alcohol electrooxidation

Bimetallic two-dimensional (2D) nanomaterials are widely used in electrocatalysis owing to their unique physicochemical properties, while trimetallic 2D materials of porous structures with large surface area are rarely reported. In this paper, a one-pot hydrothermal synthesis of ternary ultra-thin PdPtNi nanosheets is developed. By adjusting the volume ratio of the mixed solvents, PdPtNi with porous nanosheets (PNSs) and ultrathin nanosheets (UNSs) was prepared. The growth mechanism of PNSs was investigated through a series of control experiments. Notably, thanks to the high atom utilization efficiency and fast electron transfer, the PdPtNi PNSs have remarkable activity of methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). The mass activities of the well-tuned PdPtNi PNSs for MOR and EOR were 6.21 A mg-1 and 5.12 A mg-1, respectively, much higher than those of commercial Pt/C and Pd/C. In addition, after durability test, the PdPtNi PNSs exhibited desirable stability with the highest retained current density. Therefore, this work provides a significant guidance for designing and synthesizing a new 2D material with excellent catalytic performance toward direct fuel cells applications.

Preparation and characterization of PMT-TiO2-NTs@NiO-C/Sn-Sb composite electrodes by a two-step pulsed electrodeposition method for the degradation of crystalline violet

To overcome the limitations imposed by Sn-Sb electrodes, the titanium foam (PMT)-TiO₂-NTs@NiO-C/Sn-Sb composite electrodes with cubic crystal structure are synthesized by introducing NiO@C nanosheet arrays interlayer on the TiO₂-NTs/PMT matrix through hydrothermal and carbonization process. Then a two-step pulsed electrodeposition method is used to prepare the Sn-Sb coating. Benefiting from the advantages of stacked 2D layer-sheet structure, the obtained electrodes exhibit enhanced stability and conductivity. Synergy of inner and outer layers fabricated by different pulse times strongly influence the electrochemical catalytic properties of the PMT-TiO₂-NTs@NiO-C/Sn-Sb (Sn-Sb) electrode. Hence, the Sn-Sb (b0.5 h + w1 h) electrode is the optimal electrode to degrade the Crystalline Violet (CV). Next, the effect of the four experimental parameters (initial CV concentration, current density, pH value and supporting electrolyte concentration) on the degradation of CV by the electrode are investigated. The degradation of the CV is more sensitive to alkaline pH, and the rapid decolorization of CV when the pH is 10. Moreover, the possible electrocatalytic degradation pathway of CV is performed using HPLC-MS. Results from the tests show that the PMT-TiO₂-NTs/NiO@C/Sn-Sb (b0.5 h + w1 h) electrode is an interesting alternative material in industrial wastewater applications.

Electrochemical oxidation of chloramphenicol by modified Sm-PEG-PbO2 anodes: Performance and mechanism

Chloramphenicol (CAP) is used extensively in industry and daily life, but its abuse has seriously affected the environment and public health. In this paper, a new composite PbO₂ electrode was obtained through the modification Sm and polyethylene glycol (PEG), and an electrocatalytic oxidation technology of CAP degradation was investigated. The results showed that the catalytic degradation ability and industrial service life of the PEG-Sm-PbO₂ composite electrode were significantly enhanced. Co-doping inhibited the growth of grains, resulting in the formation of refined pyramidal grains on the surface of the electrode, which increased the number of active spots. The industrial service life of the modified electrode was improved by 87.0%. In addition, the degradation effect under different conditions and mechanism of CAP were also explored. The optimal conditions for CAP degradation were explored, at which time the CAP degradation rate reached 99.1%. The degradation process was in accordance with the primary reaction kinetics, and the apparent rate constant of CAP at the PEG-Sm-PbO₂ electrode was raised by 57.1% in comparison with the unmodified electrode, indicating that the modification facilitated the degradation of CAP in the electrode. Finally, two possible CAP degradation pathways were deduced. The results will provide technical support and a theoretical basis for the degradation of persistent organic pollutants.

Environmental and economic assessment of advanced oxidation for the treatment of unsymmetrical dimethylhydrazine wastewater from a life cycle perspective

As a high-performance liquid rocket fuel, unsymmetrical dimethylhydrazine (UDMH) will produce wastewater during transportation, storage and cleaning containers. The wastewater will have a bad impact on human health and ecological environment, and it must be properly handled. There are many reports about the technical feasibility of UDMH wastewater treatment. Less attention is paid to analyzing the impact on the environment during the treatment process. This paper quantifies the environmental impacts and economic benefits of four advanced oxidation processes for the treatment of UDMH wastewater based on life cycle assessment and life cycle costing methods. Taking the UDMH wastewater produced by an aerospace group of Tianjin, China as the research object, using Fenton method, UV-Fenton method, electro catalytic oxidation (EC) with ruthenium iridium titanium (Ti/TiO₂-RuO₂-IrO₂) as electrode and electro catalytic oxidation with boron-doped diamond (BDD) as electrode as treatment methods, on the basis of the laboratory test, the industrialized device is adopted. The resource consumption, energy consumption, pollutant discharge and cost were compared when the TOC removal rate was the same, and a better method of treating unsymmetrical dimethyl hydrazine wastewater was discussed. The results show that the impact on most types of environments is as follows: UV-Fenton < Fenton < EC (BDD) < EC (Ti/TiO₂-RuO₂-IrO₂), and the four advanced oxidation methods are all beneficial to reduce eutrophication. The life cycle cost of UV-Fenton is the lowest (US$1.53/m³). Combined with environmental and economic analysis, it can be seen that UV-Fenton is the best choice. Through sensitivity analysis, it can be seen that reducing chemical reagents and electricity consumption, and changing the way of generating electricity to renewable energy can significantly reduce the environmental and economic impact. The life cycle cost of EC(BDD) as the electrode is the highest (US$26.20/m³), but it can achieve a TOC removal rate of 97.75 %, so it is a better choice when only the removal rate is required regardless of cost.

Efficient removal of recalcitrant naphthenic acids with electro-cocatalytic activation of peroxymonosulfate by Fe(III)-nitrilotriacetic acid complex under neutral initial pH condition

This work investigated the activation of peroxymonosulfate by electrochemical (EC) system assisted with Fe(III)-nitrilotriacetic acid (NTA) complex for degradation of persistent naphthenic acids (NAs) under neutral initial pH conditions. As NAs are a complicated mixture, 1-adamantanecarboxylic acid (ACA) was selected as the model NA compound for degradation experiment. The addition of NTA is to chelate with Fe(III), gaining stability under neutral pH condition to facilitate the circulation of Fe(II)/Fe(III) by the electrochemical process to activate PMS. The EC/Fe(III)-NTA/PMS system was explored with applicable pH range of 3-9 and an optimized molar ratio 1: 2 for Fe: NTA. Results of quenching and chemical probe experiment together with results of electron paramagnetic resonance (EPR) analysis revealed the main reactive species of the system, including ^•OH, SO₄^•-, ¹O₂ and possibly Fe(IV). With the addition of NTA, the yields of ^•OH, SO₄^•-, ¹O₂ were enhanced. Results of mass spectrometry analysis and DFT calculations indicated the formation of 9 degradation byproducts of ACA via three primary degradation pathways such as hydroxyl substitution, carbonyl substitution, and decarboxylation. Furthermore, the EC/Fe(III)-NTA/PMS system could achieve excellent removal efficiency of ACA with different anions such as Cl^-, HCO₃^-, NO₃^- and H₂PO₄^- in the background. The practical applicability of the system was also verified with the high removal of commercial NAs mixture standard. Overall results have indicated the EC/Fe(III)-NTA/PMS system could be utilized for efficient reclamation of authentic oil and gas industrial wastewater under natural pH conditions.

Constant current-exponential attenuation mode: A non-traditional power supply mode for electrocatalytic oxidation

Low average current efficiency (ACE) and high energy consumption (EC) have seriously hindered the industrial development of electrocatalytic oxidation (ECO) technology. Timely adjustment of the current output according to the attenuation law of the organic pollutants concentration during the reaction process can help to solve the low electrical energy utilization problem at source. In this study, a non-traditional power supply mode with "constant current-exponential attenuation" (Mode CC-EA) was proposed and applied to intermittent ECO systems. The current is first output in a constant state and then attenuated exponentially according to the decreasing law of pollutants concentration, enabling efficient use of electrons at all stages of the reaction, resulting in increased degradation rates and ACE, and reduced EC. Acidic red G (ARG) was used as the target pollutant and the degradation effects of the traditional constant current mode (Mode CC), the direct exponential attenuation mode (Mode EA) and the Mode CC-EA were compared with different evaluation parameters. The results showed that the optimized Mode EA (n₄) and Mode CC-EA (70-n₁₁) degraded ARG with an ACE of 5.28 and 6.09%, respectively, which were 1.26 and 1.45 times higher than Mode CC (4.2%). At the same time, the EC were 0.36 and 0.27 kWh gCOD^-1, respectively, which were 12.2 and 34.2% lower than Mode CC (0.41 kWh gCOD^-1). The parameters of Mode CC-EA were further optimized and used for the degradation of three typical dye wastewaters, crystal violet (CV), methylene blue (MB) and methyl orange (MO), to investigate their general applicability. The results showed that the optimized Mode CC-EA achieved higher decolorization rates, chemical oxygen demand (COD) and total organic carbon (TOC) removal rates for the four wastewaters, including ARG, than Mode CC within 120 min for the same total input charge. The ACE of Mode CC-EA was on average 1.3 times higher than that of Mode CC, while the EC was on average 25.3% lower. Mode CC-EA achieves efficient use of electrical energy while ensuring the catalytic effect, which is of great application for the efficient treatment of dye wastewater and significance for the industrial development of ECO technology.

Three-dimensional structured electrode for electrocatalytic organic wastewater purification: Design, mechanism and role

Considering the growing need in decentralized water treatment, the application of electrocatalytic processes (EP) to achieve organic wastewater purification will be dominant in the near future due to high efficiency, small reactor assembly as well as the flexibility of operation and management. The catalytic performance of electrode materials determines the development of this technology. Among them, the unique three-dimensional (3D) structure electrode shows better performance than two-dimensional (2D) electrode in increasing mass transfer, enhancing adsorption and exposing more active sites. Hence, this review starts with the introduction of definition, classification, advantages and disadvantages of 3D electrode materials. Then a critical discussion on the design and construction of 3D electrode materials for organic wastewater purification application is provided. Next, the removal mechanism of organic pollutants on the surface of 3D electrode, the role of 3D structure, the design of reactor with 3D electrode, the conversion and toxicity of degradation products, electrode energy efficiency, stability and cost, are comprehensively reviewed. At last, current challenges and future perspectives for the development of 3D electrode materials are addressed. We deem that this review will provide a valuable insight into the design and application of 3D electrodes in environmental water purification.

Fabrication of a SnO2-Sb nano-pin array anode for efficient electrocatalytic oxidation of bisphenol A in wastewater

Electrocatalytic oxidation is a promising technology for eliminating bio-recalcitrant organic pollutants; however, the low efficiency and poor durability of the anodes hinder its practical application. Herein, a SnO₂-Sb nano-pin array (NPA) was fabricated on a RuO₂-based dimensionally stable anode (DSA) via a new hydrothermal-electrodeposition route to prepare a novel anode (SnO₂-Sb NPA). Compared with the conventional SnO₂-Sb/DSA and SnO₂-Sb/Ti anodes, the new SnO₂-Sb NPA anode possessed twice the electroactive surface area and a higher electron transfer efficiency for electrocatalytic reactions. The SnO₂-Sb NPA anode exhibited more than twice the rate constant of bisphenol A (BPA) degradation (0.026 min^-1) and a 120 times prolonged service life in comparison to the conventional SnO₂-Sb/Ti anode. Moreover, the SnO₂-Sb NPA anode performed well in removing BPA from actual wastewater. The mechanism of electrocatalytic degradation involves direct oxidation via electron transfer through the nano-pin surface and oxidation by in situ generated •OH radicals.

Characterization of electrodes modified with sludge-derived biochar and its performance of electrocatalytic oxidation of azo dyes

Pyrolysis of waste sludge in sewage treatment can achieve a substantial reduction in solid waste and obtain sludge-based biochars with multiple functions. However, the electrochemical properties of sludge-derived biochar as electrode modification material and the electrocatalytic ability of biochar-modified electrodes are still unclear. In this study, sludge-based biochars were prepared at various pyrolysis temperatures (400 °C, 500 °C, 600 °C, 700 °C, and 800 °C) and then were cast on glassy carbon electrodes to fabricate composite biochar-electrodes (GC400, GC500, GC600, GC700, and GC800). The results of elemental analysis and Raman spectra showed that sludge-based biochar prepared at higher temperatures exhibited higher aromaticity and degree of defect structures. And the results of cyclic voltammetry and electrochemical impedance spectra confirmed that biochar-modified electrodes prepared at higher temperatures (>600 °C) possessed better electrocatalytic activity and electrochemical stability, and their higher oxygen evolution potential than control test could improve the electrocatalytic efficiency. In the electrocatalytic oxidation of methyl orange, the removal rate with GC800 was the highest, reaching 94.49% within 240 min, and the removal rates with other composite electrodes were 90.61% (GC700) > 86.96% (GC600) > 80.32% (GC). The free radical quenching experiment revealed that the electrocatalytic degradation of methyl orange mainly depended on the indirect oxidation of hydroxyl radicals generated by electrocatalysis, accounting for 81.3% of the removal rate. The biochar-modified electrode not only greatly improved the electrocatalytic ability of the electrode for the degradation of azo dyes, but also achieved the recycling application of products after pyrolysis of sludge waste.

Mechanism and efficiency research of P- and N-codoped graphene for enhanced paracetamol electrocatalytic degradation

Electrocatalytic oxidation is an effective technology for treatment of refractory organic pollutants, and its performance strongly depends on anode materials. Among all anode materials, graphene (GN) owns the advantages of high stability and lack of secondary pollution. The catalytic performance of GN can be further improved through heteroatom doping. Here, P/N-codoped graphene (PN-GN) materials were optimized and used as an anode material for 4-acetamidophenol (APAP) electrocatalytic degradation. Result indicated that PN-GN had lower internal resistance, larger specific surface area, and higher electrochemical activity than single-doped graphene materials. The catalytic activity of GN was greatly improved by P/N codoping. When PN-GN (P8.4%-N7.6%-500 °C) was used as catalyst (current of 20 mA, initial pH of 7, reaction time of 60 min), the degradation efficiency of APAP reached 98.2% ± 1.8%, which was 17.9% ± 3.6% higher than P-codoped graphene (P-GN), 14.7% ± 4.6% higher than N-codoped graphene (N-GN), and 54.0% ± 5.2% higher than GN. After 180 min of reaction, the degradation efficiency of total organic carbon (TOC) was 78.5%. The reaction conditions were optimized and the degradation pathway of APAP was estimated to elucidate the catalytic mechanism. The main active substances generated in the system were identified as active chlorine and O₂^•-.

Waste coal cinder catalyst enhanced electrocatalytic oxidation and persulfate advanced oxidation for the degradation of sulfadiazine

Waste coal cinder, a kind of waste cinder discharged from coal combustion of thermal power plants, industrial and civil boilers, and other equipment, was rich in metal oxides with catalytic activity. In this work, waste coal cinder was used to enhance electrochemical coupling peroxymonosulfate (PMS) advanced oxidation degradation of sulfadiazine (SD). The surface morphology, elemental composition, and electrocatalytic activity of waste coal cinder were characterized by various characterization instruments. The results show that compared with simple electrocatalytic oxidation, electrocatalytic oxidation + waste coal cinder and electrocatalytic coupled persulfate oxidation, electrocatalytic oxidation + PMS advanced oxidation + waste coal cinder has the largest removal efficiency (99.95%) and mineralization rates (90.16%) of SD in 90 min, indicating that the introduction of waste coal cinder greatly increases the degradation efficiency. •OH and SO₄^-• were detected during the process of degradation. The optimal degradation process parameters were explored through different voltage, pH, plate spacing, aeration flow rate, potassium peroxymonosulfate sulfate complex salt dose, and Na₂SO₄ dosage. Cycling experiments show waste coal cinder has good structural stability. Through the analysis of triple quadrupole liquid chromatography-mass spectrometry (LC-MS), we put forward three possible ways of SD degradation. This research will provide a novel vision for water treatment.

A novel electrocatalytic system with high reactive chlorine species utilization capacity to degrade tetracycline in marine aquaculture wastewater

The problems of high salinity and coexistence of antibiotics in mariculture wastewater pose a great challenge to the traditional wastewater treatment technology. Herein, an electrocatalytic system based on cathodes to sustain reactive chlorine species (RCS) in a high chlorine environment was proposed. The results show that the content of RCS is affected by cathodes. The electrocatalytic system with FeNi/NF as cathode has the largest RCS retention capacity when compared with other cathode systems (carbon felt, nickel foam, copper foam, stainless steel, and nickel-iron foam). This is related to FeNi/NF's higher hydrogen production activity, which inhibits the reduction reaction of RCS. Furthermore, the degradation of tetracycline by the proposed FeNi/NF system maintained long-term effective performance across 20 cycles. Thus, the application of high chlorine resistance electrocatalysis system provides a possibility for practical electrocatalysis treatment of mariculture wastewater.

Singlet oxygen-dominated electrocatalytic oxidation treatment for the high-salinity quaternary ammonium compound wastewater with Ti/(RuxIry)O2 anode

The widespread application of quaternary ammonium compounds (QAC) has posed a serious hazard to the environment and human being, and high concentration of Cl^- in QAC wastewater may further increase the difficulty of pollutants elimination. In this study, such a QAC wastewater under high salinity conditions was chosen as the target, the prepared Ti/(Ru_xIr_y)O₂ anode exhibited favorable catalytic performance for the oxidation and mineralization of QAC under high salinity conditions. Increasing the Ru/Ir ratio of Ti-based electrode coating also slightly promoted the inner catalytic capacity. The combination of electron paramagnetic resonance (EPR) and quenching experiments indicates that ¹O₂ served as a main reactive specie in the Ti/(Ru_xIr_y)O₂ electrooxidation system. The increase of pH could decrease the removal efficiency of QAC for the reduced ¹O₂ yield, and the rise of Cl^- concentration could favor the QAC oxidation, and Cl^- was a better electrolyte to promote the oxidation of organic contaminants when compared to Na₂SO₄ or Na₂CO₃. Additionally, the conversion pathway of the model pollutant was tentatively investigated, the results demonstrated that there were almost no halogenated final products residual by electrocatalytic oxidation with Ti/(Ru_xIr_y)O₂ anode. This study not only elucidate the reaction mechanism of Ti/(Ru_xIr_y)O₂ anode electrocatalytic oxidation of high salinity QAC wastewater, but also may provide an efficacious and eco-friendly method for the treatment of high salinity QAC wastewater.

Multilayered TNAs/SnO2/PPy/β-PbO2 anode achieving boosted electrocatalytic oxidation of As(III)

Dealing with arsenic pollution has been of great concern owing to inherent toxicity of As(III) to environments and human health. Herein, a novel multilayered SnO₂/PPy/β-PbO₂ structure on TiO₂ nanotube arrays (TNAs/SnO₂/PPy/β-PbO₂) was synthesized by a multi-step electrodeposition process as an efficient electrocatalyst for As(III) oxidation in aqueous solution. Such TNAs/SnO₂/PPy/β-PbO₂ electrode exhibited a higher charge transfer, tolerable stability, and high oxygen evolution potential (OEP). The intriguing structure with a SnO₂, PPy, and β-PbO₂ active layers provided a larger electrochemical active area for electrocatalytic As(III) oxidation. The as-synthesized TNAs/SnO₂/PPy/β-PbO₂ anode achieved drastically enhanced As(Ⅲ) conversion efficiency of 90.72% compared to that of TNAs/β-PbO₂ at circa 45.4%. The active species involved in the electrocatalytic oxidation process included superoxide radical (•O₂^-), sulfuric acid root radicals (•SO₄^-), and hydroxyl radicals (•OH). This work offers a new strategy to construct a high-efficiency electrode to meet the requirements of favorable electrocatalytic oxidation properties, good stability, and high electrocatalytic activity for As(III) transformation to As(V).

Fabrication of novel three-dimensional Fe3O4-based particles electrodes with enhanced electrocatalytic activity for Berberine removal

Reasonable design of three-dimensional (3D) catalytic particle electrodes (CPEs) is crucial for achieving efficient electrocatalytic oxidation of organic pollutants. Herein, the novel Fe₃O₄/SnO₂/GO (FO/SO/GO) particle electrode has been developed and serviced to the 3D electrocatalytic berberine hydrochloride oxidation system with DSA (RuO₂-IrO₂-SnO₂/Ti) electrode as anode and GDE (gas diffusion electrode) electrode as the cathode. Compared with 2D systems and other CPEs, FO/SO/GO electrode shows excellent electrocatalytic activity and remarkable stability for BH removal, that is, the removal rate of BH is 94.8% within 90 min, and the rate constant is 0.03095 min^-1. More importantly, after five cycles, the ternary composite still maintains a strong ability to oxidize pollutants. The structural characterization and electrochemical measurement further uncover that the electron transfer ability and electrocatalytic oxidation efficiency are highly dependent on the surface structure regulation of CPEs. Furthermore, the quenching experiments show that hydroxyl radicals are the main active species in the 3D electro-Fenton (EF) system, which can oxidize BH molecules adsorbed on the surface of GO to CO₂, H₂O, or other products. The results could potentially provide new insights for designing and fabricating more stable and efficient 3D CPEs electrocatalytic removal of organic pollutants in the future.

A facile electroless preparation of Cu, Sn and Sb oxides coated Ti electrode for electrocatalytic degradation of organic pollutants

Electrocatalytic degradation of organic pollutants is an encouraging technology for wastewater treatment. To achieve practical application, electrode plate with cost effective fabrication, high catalytic efficiency and long service life is urgently required. This work prepared a CuO-SnO₂-SbO_X electrode on Ti substrate, which is achieved by ultrasonic assisted deposition of Cu layer, followed by electroless deposition of SnSb layer and finalized by calcination at 500 °C. The obtained electrode (Ti/CuO-SnO₂-SbO_X) exhibited high catalytic degradation activity and a high oxygen evolution potential (OEP) of 2.13 V, which is 0.4 V greater than that of the widely recognized Ti/SnO₂-SbO_X electrode. The oxygen evolution reaction (OER) models of active oxygen intermediate adsorption was optimized by density functional theory (DFT) calculations. The results revealed that (1) the ΔG of the OER rate-determining step was raised to 2.30 eV after Cu doping on 101 plane; (2) binding energies of the optimized surface with reactive oxygen species (ROS) were substantially decreased. Furthermore, the as-prepared electrode has a high yield of hydroxyl radical generation as evidenced by terephthalic acid detection. The potential for hydroxyl radical generation was measured to be 1.8 V at pH = 12 and 2.6 V at pH = 2.The catalytic degradation rate of methylene blue (MB) follows pseudo first order reaction kinetics, and the reaction constant K value reached 0.02964 -k/min^-1, twice as much as that obtained from electrodeposition electrode (Ti/Cu/SnO₂-SbO_X). A degradation rate of 94.6% was achieved for MB in 100 min in the first run, and the value remained over 85% in the subsequent 10 runs. At the same conditions, the degradation rate of p-nitrophenol was over 90% in 100 min and complete mineralization was achieved in 4 h.

A new electrochemical method for simultaneous removal of Mn2+and NH4+-N in wastewater with Cu plate as cathode

In this study, a new electrochemical method was used to simultaneously efficient removal of Mn²⁺ and NH₄⁺-N in wastewater with Cu plate as cathode. The effects of various reaction parameters on the concentrations of Mn²⁺, NH₄⁺-N and by-products (NO₃^--N and NO₂^--N, free chlorine and residual chlorine), as well as the removal mechanism were investigated. The results showed that the removal efficiencies of Mn²⁺ and NH₄⁺-N were 99.1% and 92.9%, and the concentrations of NO₃^--N, NO₂^--N, free chlorine and residue chlorine were 0.73 mg/L, 0.15 mg/L, 0.13 mg/L and 0.63 mg/L reacting for 3 h at room temperature, respectively, when the current density was 10 mA/cm², the mass ratio of ClO^- and Cl^- was 1:1, the initial pH was 9. The concentrations of Mn²⁺, NH₄⁺-N and by-products in wastewater met the integrated wastewater discharge standard (GB8978-1996). In addition, spherical manganese oxide was deposited on the anode plate, and spherical manganese oxide collapsed over electrolysis time. Manganese was mainly removed in the form of MnO, Mn(OH)₂ and MnO₂. NH₄⁺-N was mainly oxidized to N₂. Economic evalution revealed that the treatment cost was 2.93 $/m³.

Electrocatalytic oxidation of PCP-Na by a novel nano-PbO2 anode: degradation mechanism and toxicity assessment

This study aims at investigating the electrocatalytic oxidation of sodium pentachlorophenate (PCP-Na) using a novel nano-PbO₂ powder anode. The nano-PbO₂ powder (marked as HL-PbO₂) was prepared by a simple hydrolysis process, and hydrothermal treatment was followed to improve the activity of HL-PbO₂. The HL-PbO₂ treated for 24 h by hydrothermal process (HL/HT-PbO₂-24) was confirmed to possess higher crystallinity, higher oxygen evolution potential, and more active sites, resulting in stronger OH radical generation capacity and higher electrochemical activity. Compared with conventional electrodeposited PbO₂ (ED-PbO₂) anode, the HL/HT-PbO₂-24 anode showed higher PCP-Na degradation rate. Under the same operating conditions, the mineralization current efficiency at HL/HT-PbO₂-24 was 2.7 times than that at ED-PbO₂. Five intermediates were detected in PCP-Na degradation solution and possible degradation mechanism of PCP-Na was discussed. In addition, the acute toxicity of PCP-Na degradation solution to zebrafish embryos and the oxidative stress induced in zebrafish embryos/larvae were studied to evaluate the ecological security of electrocatalytic oxidation of PCP-Na.

Electrocatalytic degradation of perfluoroocatane sulfonate (PFOS) on a 3D graphene-lead dioxide (3DG-PbO2) composite anode: Electrode characterization, degradation mechanism and toxicity

In this work, a three-dimension grapnene-PbO₂ (3DG-PbO₂) composite anode was prepared using coelectrodeposition technology for electrocatalytic oxidation of perfluorooctane sulfonate (PFOS). The effect of 3DG on the surface morphology, structure and electrocatalytic activity of PbO₂ electrode was investigated. The results indicated that the 3DG-PbO₂-0.08 anode (3DG concentration in electrodeposition solution was 0.08 g L^-1) possessed the best electrocatalytic activity due to its stronger ·OH radicals generation capacity, more active sites and smaller charge-transfer resistance. The degradation rate constant of PFOS on 3DG-PbO₂-0.08 anode was 2.33 times than that of pure PbO₂ anode. Additionally, the by-products formed in electrocatalytic degradation of PFOS were identified and a PFOS degradation pathway was proposed accordingly, which was dominated by the dissociation of -CF₂- groups via the attack of ·OH radicals. Finally, the toxicity evolution of degradation solution was examined to evaluate the ecological risk of electrocatalytic oxidation of PFOS by acute toxicity assays to zebrafish embryos.

Degradation characteristics of dissolved organic matter in nanofiltration concentrated landfill leachate during electrocatalytic oxidation

Nanofiltration concentrated landfill leachate (NCLL) is produced during the integration process of biodegradation and nanofiltration, containing a large amount of recalcitrant dissolved organic matter (DOM). In this work, electrocatalytic oxidation technology was employed to degrade DOM in NCLL and spectroscopic technology was applied to explore the structural changes. The results showed that under the optimal experimental condition (pH = 2.0, NaCl concentration = 0.7%, Fe₂(SO₄)₃ concentration = 0.8%, the retention time = 6 h), the removal rates of COD, TOC, and UV₂₅₄ were 99.0%, 57.4%, 99.3% respectively. Ultraviolet-Visible (UV-Vis) spectral analysis showed that aromatic CC can be effectively degraded by electrocatalytic oxidation, resulting in decreases of aromaticity and molecular weight in NCLL. Two fluorescent components (terrestrial humic-like substances and fulvic-like substances) were identified in NCLL by parallel factor analysis, which can be effectively removed by electrocatalytic oxidation with removal rates of 99.9% and 90.5%, respectively. In addition, through two-dimensional correlation spectroscopic analysis, the sequence of structural changes of the DOM in NCLL was confirmed: unsaturated double bonds → fulvic-like components/aromatic structures → terrestrial humic-like components. These spectral characterization techniques can provide a deep understanding of the degradation pathways of DOM and provide new insights for the treatment of NCLL.

Synthesis of MOF-derived Ni@C materials for the electrochemical detection of histamine

Histamine (HA) plays an important role in food safety supervision and is also involved in various physiological functions. Accurate and rapid detection of HA in real sample is count for much as this is the significant prerequisite for its effective monitoring. In this study, we fabricated an electrochemical sensor to detect HA via the pyrolysis of the hydrothermal Ni-MOF (metal-organic frameworks), in which the obtained Ni@C material was deployed as the sensing agent. Ni@C was comprehensively characterized in terms of its morphology, constitution, as well as its electrochemical behavior. The as-prepared sensor (Ni@C/GCE) features excellent electrocatalytic activities. It was also observed that the electrochemical property of the sensor was substantially improved because Ni@C afforded an enlarged active surface and accelerated electron transport. This sensor affords amperometric analysis in the linear range of 10^-3-100 μM HA with a 3.2 × 10^-4 μM low detection limit (S/N = 3). Many important features, including decent anti-interference, reproducibility, stability, and reliability, were also observed. Importantly, the sensor enabled the measurement of HA in real samples obtained from fish, thus demonstrating its practical potential as a HA analytical detector.

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.

Insights into the degradation and detoxication mechanisms of aqueous capecitabine in electrochemical oxidation process

Electrocatalytic oxidation and detoxication of capecitabine (CAP) in aqueous solution were investigated with Ti/SnO₂-Sb/Ce-PbO₂ anode. The relative contributions of generated free radicals showed an increase in the pseudo zero order tare constants in the following order: OH (9.4%) < SO₄^- (24.2%) < O₂^- (53.3%). The operating parameters and solution matrixes, i.e. applied current densities, initial CAP concentrations, initial Cl^- and NO₃^- concentrations, influencing the CAP degradation efficiency were evaluated. The kinetic rate constant of 0.1404 min^-1 was found within 7 min at current density of 10 mA cm^-2 and initial CAP concentration of 20 mg L^-1, while the mineralization efficiency of 59.5%, mineralization current efficiency of 2.06%, detoxication rate to Escherichia coli of 55.5% were achieved at reaction time 90 min. The major degradation pathways of CAP were oxidation, defluorination and bond cleavage, following with the formation of carboxylic acids, NO₃^-, NO₂^-, NH₄⁺ and F^-. Electrochemical oxidation process based on Ti/SnO₂-Sb/Ce-PbO₂ anode is proved to be effective for elimination, mineralization and detoxication of aqueous CAP.

Optimized terbium doped Ti/PbO2 dimensional stable anode as a strong tool for electrocatalytic degradation of imidacloprid waste water

The presence of pesticides in water has emerged as a momentous environmental issue over the past decades. Herein, a terbium doped Ti/PbO₂ (denoted as Ti/PbO₂-Tb) dimensionally stable Ti/PbO₂-Tb anode has been successfully prepared by one-step electrodeposition path for electrocatalytic degradation of imidacloprid (IMD) wastewater with high efficiency. Ti/PbO₂-Tb electrode presents higher oxygen evolution potential, lower charge transfer resistance, stronger stability, longer service lifetime and outstanding electrocatalytic activity than Ti/PbO₂ electrode. The optimum condition for IMD oxidation is obtained by analyzing the effects of some critical operating parameters including temperature, initial pH, current density and electrolyte concentration. It is proved that 70.05% of chemical oxygen demand and 76.07% of IMD are removed after 2.5 h of degradation under current density of 8 mA cm^-2, pH 9, temperature 30 °C and 7.0 g L^-1 NaCl electrolyte. In addition, the electrode displays commendable energy saving property as well as favorable reusability. The degradation mechanism of IMD is proposed by analyzing the intermediates identified by LC-MS. The present research provides a feasible strategy to degrade IMD wastewater by Ti/PbO₂-Tb electrode.

A nickel-cobalt bimetallic phosphide nanocage as an efficient electrocatalyst for nonenzymatic sensing of glucose

The authors describe Ni-Co bimetal phosphide (NiCoP) nanocages that exhibit enhanced electrocatalytic performance toward glucose oxidation. The nanocages offer an appealing architecture, large specific area, and good accessibility for the analyte glucose. When placed on a glassy carbon electrode, the sensor exhibits attractive figures of merit for sensing glucose in 0.1 M NaOH solution including (a) a wide linear range (0.005-7 mM), (b) a low determination limit (0.36 μM), (c) high sensitivity (6115 μA•μM^-1•cm^-2), (d) a relatively low working potential (0.50 V vs. Ag/AgCl), and (e) good selectivity, reproducibility, and stability. The sensor is successfully applied to the determination of glucose in human serum samples. Graphical abstractSchematic representation of a glassy carbon electrode modified with Ni-Co bimetal phosphide (NiCoP) nanocage. NiCoP nanocage exhibits excellent electrocatalytic activity toward glucose oxidation. NiCoP nanocage is applied in a sensitive non-enzymatic glucose sensor.

A non-enzymatic amperometric glucose sensor based on the use of graphene frameworks-promoted ultrafine platinum nanoparticles

Ultrafine platinum nanoparticles are grown on a 3D graphene framework (GF-Pt) via a hydrothermal method. The material, when placed on a glassy carbon electrode (GCE), displays enhanced electrocatalytic activity towards glucose oxidation. This is assumed to be the result of the numerous easily accessible active sites, an enlarged electrochemically active area, and the presence of multiple electron/ion transport channels. The modified GCE can be operated at a low potential (- 0.15 V vs. Ag/AgCl) has linear responses in the 0.1 μM - 0.01 mM and 0.01 mM - 20 mM glucose concentration range, and a 30 nM detection limit. It was applied to the rapid determination of glucose in human serum samples. Graphical abstract Schematic presentation of a glassy carbon electrode modified with ultrafine Pt nanoparticles grown on a graphene framework (GFs-Pt). GFs-Pt presents enhanced electrocatalytic activity towards glucose oxidation. GFs-Pt is used in a sensitive non-enzymatic amperometric glucose sensor.

Electrochemical degradation of oxytetracycline by Ti-Sn-Sb/γ-Al2O3 three-dimensional electrodes

In this work, Ti-Sn-Sb/γ-Al₂O₃ particle electrodes were prepared and employed for the degradation of oxytetracycline (OTC) by three-dimensional electrocatalytic technology. Factors associated with the preparation of Ti-Sn-Sb/γ-Al₂O₃ particle electrodes were investigated. The effects of initial concentration, conductivity, pH value, aeration intensity, current density, plate spacing, and particle electrode dosage on OTC removal were studied. The removal rate of OTC and total organic carbon were achieved approximately 92.0% and 41.0% under the optimal operating condition, respectively. In addition, Ti-Sn-Sb/γ-Al₂O₃ particle electrode was analyzed by Fourier Transform Infrared spectroscopy (FT-IR), scanning electron microscope (SEM), energy dispersive spectrum analysis (EDX), X-Ray Fluorescence Spectrometer (XRF), and X Ray Diffraction analysis (XRD), which indicated that a significant amount of TiO₂, SnO₂, and Sb₂O₃ were formed on the surface of Ti-Sn-Sb/γ-Al₂O₃ particle electrode. It was also observed that the primary function of Ti-Sn-Sb/γ-Al₂O₃ particle electrode in the three-dimensional electrode electrolysis process is the strong oxidizing function of ·OH for degrading OTC. Consequently, the analysis of degradation products of oxytetracycline (OTC) demonstrates. In addition, the results and conclusions of this study provide a methodological basis and engineering practice basis for removing the low concentration of antibiotics in water.

Amperometric sensing of hydrazine by using single gold nanopore electrodes filled with Prussian Blue and coated with polypyrrole and carbon dots

A nanoprobe for hydrazine sensing is described that is making use of a single gold nanopore electrode (SAuNPEs) that was modified by electro-deposition of Prussian Blue (PB) and then coated with a thin membrane of polypyrrole and carbon dots in order to enhance stability and catalytic activity. Best operated at a low potential of 0.3 V vs. Ag/AgCl, the nanosensor display good electrocatalytic activity towards the oxidation of hydrazine, with a linear response in the 0.5-80 μM hydrazine concentration range and a 0.18 μM detection limit (at S/N = 3). The method was applied to the determination of hydrazine in human urine. Graphical abstract Schematic presentation of the electrocatalytic oxidation of hydrazine using a single gold nanopore electrode that was modified by electro-deposition of Prussian Blue and then coated with a thin membrane of polypyrrole and carbon dots.

Electrocatalytic oxidative treatment of real textile wastewater in continuous reactor: Degradation pathway and disposability study

Electrocatalytic treatment of real textile wastewater was investigated in continuous electrochemical reactor using dimensionally stable Ti/RuO₂ anode. Effects of various parameters such as: elapsed time, current, pH, retention time on the COD removal, color removal and specific energy consumed were evaluated. Central Composite Design under RSM was used for experimental design, data analysis, optimization, interaction analysis between the various electrochemical parameters and steady state time analysis. GC-MS and UV spectrophotometric analysis of the untreated and treated wastewater were conducted to identify the oxidized and transformed/degraded compounds during the oxidation process, and a suitable degradation mechanism was proposed. Treated wastewater may contain toxic chlorinated compounds due to mediated oxidation by various hydrolyzed chlorine species. Therefore, disposability of treated wastewater was assessed by conducting toxicity bioassay test. The optimal set of operating parameters were found to be elapsed time = 124 min, current = 1.37 A, pH = 5.54 and retention time = 157.6 min to simultaneously achieve COD removal, color removal and specific energy consumed as 86.22%, 94.74% and 0.012 kW h, respectively. GC-MS analysis showed presence of chlorinated compounds in the treated wastewater. The toxicity bioassay test resulted acute toxicity with 100% mortality rate within one minute and one hour exposure with untreated and treated textile wastewater, respectively.

Amperometric nonenzymatic sensing of glucose at very low working potential by using a nanoporous PdAuNi ternary alloy

The authors present a nonenzymatic sensor for glucose that has an exceedingly low working potential which makes the sensor highly selective over other electroactive species. The sensor is based on the use of a glassy carbon electrode (GCE) that was modified with a nanoporous PdAuNi alloy (np-PdAuNi). The PdAuNi alloy nanostructure displays enhanced electrocatalytic activity for glucose oxidation (compared to PdNi alloys). The modified GCE enables amperometric sensing of glucose at a typical working electrode potential of 0.0 V vs. SCE in solutions of pH 13 containing 0.1 M NaCl. Response is linear in the 5 to 100 μM concentration range, with a 1.7 μM detection limit (at an S/N ratio of 3). For higher concentrations deviations from linearity were found. The method is selective and reproducible. The modified electrode was applied to the determination of glucose in human serum. Graphical Abstract Nanoporous PdAuNi alloy with three-dimensional bicontinuous nanosponge architecture was successfully prepared via chemical dealloying. The electrochemical nonenzymatic glucose sensor shows a low working potential, wide linear range, good sensitivity, low detection limit and excellent selectivity.

A novel electrochemical sensor based on Cu@Ni/MWCNTs nanocomposite for simultaneous determination of guanine and adenine

A novel electrochemical sensing platform based on combination of multi-walled carbon nanotubes and copper-nickel hybrid nanoparticles (Cu@Ni/MWCNTs) was developed for simultaneous detection of guanine (G) and adenine (A). The Ni/MWCNTs and Cu@Ni/MWCNTs nanocomposites were characterized by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). The electrochemical behaviors of G and A on the modified electrode were explored by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffer with pH 3.0. Under the optimal conditions, electrical signals were linear over the concentration ranges from 5.0 to 180μM and 8.0 to 150μM for simultaneous determination G and A with the detection limit as low as 0.35μM and 0.56μM (S/N = 3), respectively. Furthermore, linear concentration ranges in individual determination are 1.0-180μM and 2.0-150μM with detection limits of 0.17μM and 0.33μM (S/N = 3) for G and A, respectively. The sensor was successfully used to quantify G and A in real samples. The Cu@Ni/MWCNTs composite presented here can serve as a promising candidate for developing electrochemical sensor devices and plays an important role in widespread fields.

New synthesis of poly ortho-methoxyaniline nanostructures and its application to construct modified multi-wall carbon nanotube/graphite paste electrode for simultaneous determination of uric acid and folic acid

Uric acid (UA) and folic acid (FA) are compounds of biomedical interest. In humans, about 70% of daily uric acid disposal occurs via the kidneys, and in 5–25% of humans, impaired renal (kidney) excretion leads to hyperuricemia. Folate is another form folic acid of which is known as, is one of the B vitamins. It is used as a supplement by women to prevent neural tube defects developing during pregnancy. Polyortho-methoxyaniline nanostructures (POMANS) was synthesized with a new two phase (organic-water) synthesis method. The POMANS was characterized using transmission electron microscopy (TEM) and Fourier transform IR (FTIR). This polymer was used to construct a modified multi-wall carbon nanotube, graphite paste electrode (POMANS-MWCNT/GPE). Linear sweep voltammograms (LSV), cyclic voltammetry (CV) and chronoamperometry were used to investigate the suitability of polyortho-methoxyaniline with multi-wall carbon nanotubes paste electrode as a modifier for the electrocatalytic oxidation of UA and FA in aqueous solutions with various pHs. The results showed that POMANS-MWCNT/GPE had high anodic peak currents for the electrooxidation of UA and FA in pH 6.0.Under the optimized conditions, The catalytic peak currents obtained, was linearly dependent on the UA and FA concentrations in the range of 0.6–52 and 0.5–68 μM with two segments and the detection limits 0.157 and 0.113 μM for UA and FA were, respectively. Finally, the proposed method was also examined as a sensitive, simple and inexpensive electrochemical sensor for the simultaneous determination of UA and FA in real samples such as urine and serum.

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For the first time, POMANS was synthesized with a new method of two-phase organic & water.

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POMANS-MWCNT/GPE was used for simultaneous determination of UA and FA at optimum pH 6.0.

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Parameters n and α were also determined for UA and FA.

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Electrochemical simultaneous determination of UA and FA with modified electrode real samples.

Au-Pt bimetallic nanoparticles supported on functionalized nitrogen-doped graphene for sensitive detection of nitrite

In this work, we report a novel Au-Pt bimetallic nanoparticles (Au-PtNPs) decorated on the surface of nitrogen-doped graphene (NG) functionalized with 1, 3, 6, 8-pyrene tetra sulfonic acid sodium salt (PyTS) by direct electrodeposition method. The results of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and electrochemical impendence spectrum (EIS) reveal that the Au-PtNPs were successfully anchored on the surface of NG sheets with a diameter of 20-40nm. Further, the prepared Au-PtNPs/PyTS-NG nanocomposite exhibits superior catalytic activity for the oxidation of nitrite. Under optimal experimental conditions, an amperometric sensor with a linear range of 0.5-1621μM and a detection limit of 0.19μM (S/N=3) for the detection of nitrite was set up and applied to real samples.

Non-enzymatic detection of glucose using poly(azure A)-nickel modified glassy carbon electrode

A simple, sensitive and selective non-enzymatic glucose sensor was constructed in this paper. The poly(azure A)-nickel modified glassy carbon electrode was successfully fabricated by the electropolymerization of azure A and the adsorption of Ni(2+). The Ni modified electrode, which was characterized by scanning electron microscope, cyclic voltammetry, electrochemical impedance spectra and X-ray photoelectron spectroscopy measurements, respectively, displayed well-defined current responses of the Ni(III)/Ni(II) couple and showed a good activity for electrocatalytic oxidation of glucose in alkaline medium. Under the optimized conditions, the developed sensor exhibited a broad linear calibration range of 5 μM-12mM for quantification of glucose and a low detection limit of 0.64μM (3σ). The excellent analytical performance including simple structure, fast response time, good anti-interference ability, satisfying stability and reliable reproducibility were also found from the proposed amperometric sensor. The results were satisfactory for the determination of glucose in human serum samples as comparison to those from a local hospital.

Three-dimensional roselike α-Ni(OH)₂ assembled from nanosheet building blocks for non-enzymatic glucose detection

Glucose detection plays very important roles in diagnostics and management of diabetes. The search for novel catalytic materials with appropriate architectures is the key step in the fabrication of highly sensitive glucose sensors. In this work, α-Ni(OH)2 roselike structures (Ni(OH)2-RS) assembled from nanosheet building blocks were successfully synthesized by a hydrothermal method through the hydrolysis of nickel chloride in the mixed solvents of water and ethanol with the assistance of polyethylene glycol (PEG). The structure and morphology of the roselike α-Ni(OH)2 were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and N2 adsorption-desorption isotherm measurement. TEM and FE-SEM images showed that the synthesized Ni(OH)2 was roselike and the size of the leaf-shaped nanosheet was about 5 nm in thickness, which leads to larger active surface areas and faster electron transfer for the detection of glucose. Compared with the bare GCE and bulk Ni(OH)2/GCE, the Ni(OH)2-RS/GCE had higher catalytic activity toward the oxidation of glucose. Under the optimal conditions, the Ni(OH)2-RS/GCE offers a variety of merits, such as a wide linear response window for glucose concentrations ranging from 0.87 μM to 10.53 mM, short response time (3s), a lower detection limit of 0.08 μM (S/N=3), as well as long term stability and repeatability.

Facile preparation of Ni(OH)2-MnO2 hybrid material and its application in the electrocatalytic oxidation of hydrazine

A surfactant-free synthetic methodology is reported for the preparation of Ni(OH)2-MnO2 hybrid nanostructures. For comparative study, MnO2 and Ni(OH)2 were also synthesized. Materials were characterized by X-ray diffraction, nitrogen sorption, scanning electron microscopy, and transmission electron microscopy. Ni(OH)2-MnO2 modified electrode is fabricated for the determination of hydrazine. The electrochemical oxidation of hydrazine was investigated using cyclic, linear sweep voltammetries, and chronoamperometry methods. The Ni(OH)2-MnO2 modified electrode showed hydrazine oxidation with decrease in the over voltage and increase in the oxidation peak current, when compared to MnO2, Ni(OH)2, and bare GCE. pH was optimized to obtain the best peak potential and current sensitivity. Chronoamperometry was used to estimate the diffusion coefficient of hydrazine. The kinetic parameters such as overall number of electrons involved in the catalytic oxidation of hydrazine and the rate constant (k) for the oxidation of hydrazine at Ni(OH)2-MnO2 modified electrode were determined. The Ni(OH)2-MnO2 modified electrode exhibited good sensitivity, stability, and reproducibility in hydrazine sensing.

Determination of Dopamine in the Presence of Ascorbic Acid by Nafion and Single-Walled Carbon Nanotube Film Modified on Carbon Fiber Microelectrode

Carbon fiber microelectrode (CFME) modified by Nafion and single-walled carbon nanotubes (SWNTs) was studied by voltammetric methods in phosphate buffer saline (PBS) solution at pH 7.4. The Nafion-SWNTs/CFME modified microelectrode exhibited strongly enhanced voltammetric sensitivity and selectivity towards dopamine (DA) determination in the presence of ascorbic acid (AA). Nafion-SWNTs film accelerated the electron transfer reaction of DA, but Nafion film as a negatively charged polymer restrained the electrochemical response of AA. Voltammetric techniques separated the anodic peaks of DA and AA, and the interference from AA was effectively excluded from DA determination. Linear calibration plots were obtained in the DA concentration range of 10 nM - 10 μM and the detection limit of the anodic current was determined to be 5 nM at a signal-to-noise ratio of 3. The study results demonstrate that DA can be determined without any interference from AA at the modified microelectrode, thereby increasing the sensitivity, selectivity, and reproducibility and stability.