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Expanding voluntary social insurance coverage is one of the important goals of the social insurance system in Vietnam and many developing countries around the world. This study uses a combination of document research methods, traditional statistical analysis methods; synthesize, compare, contrast, and clarify the theoretical basis for the expansion of voluntary social insurance coverage, the legal provisions on voluntary social insurance policies and the current status of voluntary social insurance coverage in Vietnam. Based on the research results, the authors propose some recommendations to improve the policy and organize the implementation of social insurance, aiming to expand the coverage of voluntary social insurance. Recommendations include: financial incentives through participation and support from the Government, adding short-term benefits to the voluntary social insurance program, reforming administrative procedures and boosting investment application of information technology in the management of the social insurance system, and strengthening communication on voluntary social insurance.

The reliability of financial statements is important to many people such as investors, corporate shareholders, and auditors. A reliable financial report is free from problems of fraud and manipulation by corporate management. Using the methodology and meta-analysis, the research team found that the application of the M-score model in Vietnam is not yet popular. The number of research papers on the M-score model is small and there is no research using this model to assess the reliability of financial statements. Research results with actual data from the unaudited financial statements of a typical enterprise show that the application of the M-score model to assess the reliability or detect fraud of financial statements is an appropriate fit. However, the research team also found that the M-score model also has a high probability of incorrect identification of unreliable financial statements. Therefore, from the research results, we recommend that investors, shareholders, and stakeholders use a combination of the M-score model together with other technical analysis tools to be able to identify whether a financial statement is reliable.

In this study, the authors proposed a model to study the factors affecting compliance with the law on social insurance of non-state enterprises in Vietnam. The study uses a combination of document review methods, traditional statistical and analytical methods for secondary sources of agencies and organizations, and qualitative research methods (in-depth interviews with research subjects); the research team has screened and selected the main factors suitable to the research context, proposed a research model of factors affecting the level of compliance with the law on social insurance of non-state enterprises in Vietnam. The research model is built including six independent variables (the possibility of being inspected and examined by social insurance, penalties for violations of social insurance, social influence, corporate finance, corporate reputation, social insurance policies, and procedures) and a dependent variable (compliance with the law on social insurance of non-state enterprises). The results of this study are the basis and the premise for the next formal quantitative studies.

The article has provided the content and function of the Z-score model in predicting the possibility of bankruptcy through the actual financial situation of the enterprise. The study uses two research methods, namely the analytical method and the meta-analytic method. Through the methodology, the team obtained an overview of the study and identified gaps in which to conduct the research. Next, the research team aelected a sample of 9 garment manufacturing companies listed on the Vietnamese stock market. Combining the collection of secondary data from financial statements and the theory of the Z-score model, we have a basis to evaluate the financial situation of these 9 enterprises in 2022. 4 enterprises having in good financial condition, 4 enterprises with difficult financial situations and 1 enterprise with financial distress consistent with the actual situation of all 9 enterprises. The analysis results also show that the Z-score model is reliable and quite effective in assessing financial health and predicting the bankruptcy of enterprises.

In this study, the authors proposed a model to study the influencing factors and determine the level and direction of the factors affecting compliance with the law on social insurance of non-state enterprises in Vietnam. The research model is tested with a survey data set of research subjects in Hanoi and the provinces of the Red River Delta, Vietnam. Research results have confirmed the positive impact and level of impact of five factors affecting the compliance with the law on social insurance of non- state enterprises, arranged in order of decreasing importance as follows: the possibility of being inspected and examined by social insurance, corporate reputation, corporate finance, penalties for violations of social insurance and social influence. Based on the research results, the authors have proposed several solutions to improve the level of compliance with the law on social insurance of non-state enterprises.

In Vietnam, in recent years, the situation of employees stopping participating in social insurance and withdrawing one- time social insurance before retirement age tends to increase. The article uses the literature review method and the in-depth interview method to determine the factors related to receiving one-time social insurance for employees in Vietnam. The research results are used as a basis for building a research model, adjusting and supplementing the scale of factors affecting the intention to receive one- time social insurance of employees in Vietnam based on inheriting previous studies previously saved.

Applying the servqual model (Parasuraman et al., 1988), in this study, the authors proposed a model to assess customer satisfaction with the quality of public services at the insurance agency in Lao Cai province, Vietnam. The study used a combination of qualitative and quantitative research methods. The research model is tested with the survey data of customers participating in using public services at the social insurance agency of Lao Cai province. The results of the regression anal ysis show that the five factors affecting customer satisfaction with the quality of public services at the social insurance agency are arranged in order of decreasing importance as follows: responsiveness, service capacity, empathy, reliability, and tangible means.

The article has provided a theoretical basis for internal control, internal control system in general and internal control system in enterprises in Vietnam. This study also presents the background theories as a basis to explain the impact of factors on the effectiveness of the internal control system, which are: Theory of regulation; delegation theory; institutional theory, uncertainty theory of organizations, and psychosocial theory of organizations. Based on the theoretical basis system that has been built and the underlying theories, the research team has built a proposed research model on the factors affecting the effectiveness of the internal control system in the company. Vietnamese life insurers, including: control environment, risk assessment, control activities, information and communication, and supervision., {"references":["Alvin A. Arens & James K. Loebbecke, (2000). Audit. Hanoi: Statistical Publishing House. 2) Ministry of Finance, (2001). Decision No. 143/2001/QD-BTC dated 21/12/2001, Vietnam Auditing Standard No. 400. 3) Ministry of Finance, (2012). Circular No. 214/2012/TT–BTC dated December 6, 2012, Auditing Standard No. 315. 4) Ahmad, Kamilah & Mohamed Zabri, Shafie, (2015). Factors explaining the use of management accounting practices in Malaysian medium-sized firms. Journal of Small Business and Enterprise Development 22. 4 (2015): 762-781. 5) Allan J. Cigler and Burdett A.Loomis, (1995). Interest Group Politisc, Congressional Quarterly Presss: 89. 6) Anderson N, ( 1981). Foundations in Integration Theory. Academic Press. New York. 7) Angella Amudo, Eno L. Inanga, (2009). Evaluation of Internal Control Systems: A Case Study from Uganda, International Research Journal of Finance and Economics, 27:125-144. 8) Anthony, R.N; Dear, J. and Bedford, N.M, ( 1989). Management Control System, Irwin, Homewood, IL 9) Ashbaugh-Skaife, H., Collins, D. W., Kinney, W. R., & LaFond, R., (2008). The effect of SOX internal control deficiencies and their remediation on accrual quality. The Accounting Review, 83 (1): 217-250. Risk assessment Control operation Information and communication Monitor Efficiency of internal control system in business in Vietnam Control environment Constructing a Model for Assessment of Factors Affecting the Efficiency of Internal Control System in Businesses in Vietnam IJMRA, Volume 06 Issue 02 Febraury 2023 www.ijmra.in Page 735 10) DiNapoli, T. P, (2007). Standards for Internal Control In New York State Government. 11) Spinger.L.M, (2004). Revisions to OMB Circular A-123, Management's Responsibility for Internal Control. Available at http://www.whitehouse.gov/omb/index.html"]}

Health insurance is an important social policy with humanitarian meaning and profound community sharing, which is highly valued and promoted by the Vietnamese Government in the social security policy system. Therefore, it is necessary to study users’ satisfaction to medical examination and treatment services with health insurance cards. Based on the questionnaire surveys, the research team conducted Cronbach's Alpha analysis of each factor, assessed the scale reliability. Multivariate regression and ANOVA test showed that all four components: health services, human resources, medical examination and treatment costs, medical information and medical products positively affected users’ satisfaction to medical examination and treatment services with health insurance cards in Ninh Binh province, Vietnam. Based on the survey results and the information exchanged directly with people who came for medical examination and treatment, the research team drew out shortcomings in medical examination and treatment for users of health insurance card sin Ninh Binh province. Shortcomings in medical examination and treatment with health insurance cards were pointed out as an important basis for proposals to improve the medical examination and treatment quality for insured subjects including: Health insurance costs and response levels; Medical examination and treatment process with health insurance and doctor’s responsibility. Reasonable waiting time and hospital environment; Health insurance-based drug delivery.&nbsp

An energy-efficient Magneli phase Ti4O7 reactive electrochemical membrane (REM) was applied for the oxidation of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Approximately...

International audience; The mediated electrochemical reduction of NAD(P) + in aerated solution was investigated and exploited for NAD(P)H regeneration in view of biosensing application. Oxygen was locally removed from the electrode surface with an electrochemical oxygen filter made of platinum grids positioned close to the oxygen sensitive reactions. The working electrode was a bucky paper functionalized with [Cp*Rh(bpy)Cl] + by diazonium electrografting. The local oxygen removal was first evaluated, before to be applied to deoxygenation for NAD + and NADP + reduction. A porous silica gel layer encapsulating D-sorbitol dehydrogenase was finally deposited on the top of the modified bucky paper and the resulting bioelectrode was found sensitive to the presence of D-fructose.

International audience; An electrochemical oxygen filter is described that removes efficiently dissolved oxygen from the surface of an electrochemical sensor. Simulations show that 99 % of oxygen can be removed in less than 60 s if an electrochemical filter made of a porous electrode is positioned at less than 200 µm from the sensor surface. For experimental demonstration, the metallic filter was made with either a stainless steel or a platinum grids separated from the sensor by a porous separator. It was combined with a sensor for analysis of paraquat, an herbicide widely used over the world. In aerated solutions, paraquat signal was not distinguished due to the strong interference of oxygen. When using the oxygen filter, paraquat was clearly detected with a better-defined response than the one obtained under N2 atmosphere that requires longer time before analysis.

International audience; A bioelectrode for electroenzymatic synthesis was prepared, combining a layer for NADH regeneration and a renewable layer for enzymatic substrate reduction. The covalent immobilization of a rhodium complex mediator ([Cp*Rh(bpy)Cl]+) on the surface of a bucky paper electrode was achieved by following an original protocol in two steps. A bipyridine ligand was first grafted on the electrode by electro‐reduction of bipyridyl diazonium cations generated from 4‐amino‐2,2′‐bipyridine, and the complex was then formed by reaction with [RhCp*Cl2]2. A turnover frequency of 1.3 s−1 was estimated for the electrocatalytic regeneration of NADH by this immobilized complex, with a Faraday efficiency of 83 %. The bucky paper electrode was then overcoated by a bio‐doped porous layer made of glassy fibers with immobilized D‐sorbitol dehydrogenase. This assembly allowed for the efficient separation of the enzyme and the rhodium catalyst, which is a prerequisite for effective bioelectrocatalysis with such bioelectrochemical system, while allowing effective mass transport of NAD+/NADH cofactor from one layer to the other. Thereby, it was possible to reuse the same mediator‐functionalized bucky paper with three different enzyme layers. The bioelectrode was applied to the electroenzymatic reduction of D‐fructose to D‐sorbitol. A turnover frequency of 0.19 s−1 for the rhodium complex was observed in the presence of 3 mM D‐fructose and a total turnover number higher than 12000 was estimated.

International audience; The future of fuel cells that convert the chemical energy to electricity relies mostly on the efficiency of oxygen reduction reaction (ORR) due to its sluggish kinetics. By 2effectively bypassing the use of organic surfactants, post-synthesis steps for the immobilization onto electrodes, the catalytic inks preparation using binders, and the common problem ofnanoparticles detachment from supports involved in traditional methodologies, we demonstrate a versatile electrodeposition method for growing anisotropic microstructures directly onto a threedimensional (3D) carbon felt electrode, using platinum nanoparticles as elementary building blocks. The as-synthesized materials were extensively characterized by integrating methods of physical (TGA, XRD, SEM, ICP, XPS) and electroanalytical (voltammetry, EIS) chemistry to examine the intricate relationship of material-to-performance and select the best-performing electrocatalyst to be applied in the model reaction of ORR for its practical integration into a microbial fuel cell (MFC). A tightly optimized procedure enables decorating an electrochemically activated carbon felt electrode by 40-60 nm ultrathin 3D-interconnected platinum nanoarrays leading to a hierarchical framework of ca. 500 nm. Half-cell reactions reveal that the highly rough metallic surface exhibits improved activity and stability towards ORR (Eonset ~1.1 V vs. RHE, p(HO2‒) < 0.1%) and hydrogen evolution reaction (HER, -10 mA cm−2 for only 75 mV overpotential). Owing to its unique features, the developed material showed distinguished performance as an air-breathing cathode in a garden compost MCF exhibiting better current and faster power generation than its equivalent classical double chamber. The enhanced performance of the material obtained herein is explained by the absence of any organic surfactant on the surface of the nanoarrays, the good metal-support interaction, the particular morphology of the nanoarrays, and the reduced aggregation/detachment of particles. It promises a radical improvement in current surface reactions and paves a new way towards electrodes with regulated surface roughness allowing for their successful application in heterogeneous catalysis

International audience; We present the effect of thermal treatment of carbon felt by gas flow containing 1% of oxygen at high temperature on the direct electron transfer and electrocatalytic oxygen reduction currents by a bilirubin oxidase (BOD) film directly adsorbed in the presence of carbon nanotubes on to a porous carbon felt (PCF). The upgraded properties (surface area, pore volume and hydrophilicity) of the resulting porous carbon felt (PCF) in comparison to commercial carbon felt (raw CF), creates a suitable support for the entrapment of MWCNTs bearing negative charges at neutral pH and BOD enzymes, all the components being entrapped in chitosan layer reticulated with glutaraldehyde. Since functional MWCNTs are 2 usually used to facilitate DET, we introduce COOH@MWCNTs, bearing negative charges at neutral pH, in the enzyme layer to evaluate their impact on the electron transfer properties with BOD. The enzyme immobilization efficiency is examined by varying the amount of the components and the immobilization procedure. Linear sweep voltammetry (LSV) and chronoamperometry measurements are used to evaluate the electrochemical behavior of the enzymatic biocathodes. Based on the experimental results, we show that the optimized bioelectrode delivers a current density of 3.70 mA cm-2at 0.15 V vs Ag/AgCl and could retain above 55 % of its initial response after 4 months, proving its outstanding performance. This new bioelectrode allows for optimal DET-type bioelectrocatalytic activity toward O2 reduction and is a very promising candidate for the construction of 3-dimensional cathodes in (bio)-electrochemical devices needing high current output.

Catalytic electrodes were prepared via carbonization of MIL-53(Fe) on the surface of porous carbon felt electrodes (CF) for use in wastewater treatment by the heterogeneous electro-Fenton (EF) process. The best results were obtained when the carbon felt was pretreated with nitric acid, enhancing the affinity of the MIL-53(Fe) for the surface. Following a series of optimization experiments, carbonization conditions of 800 &deg, C for 5 h were used to form Fe-nanoporous carbon (MOFs@CF). The as-prepared electrodes were used as both cathode and heterogeneous catalyst in the EF process for the mineralization of exemplar dye Acid Orange 7 (AO7). Total organic carbon (TOC) removal of 46.1% was obtained within 8 h of electrolysis at around neutral pH (6.5) and the electrode retained over 80% of its original efficiency over five treatment cycles.

International audience; Commercial carbon felt (CF) substrates have been modified with iron-rich MFI zeolite nanoseeds prepared by a solvothermal microwave-assisted synthesis method. The as-prepared material (MFI@CF) was characterized by TGA, XRD, SEM, and used as both cathode and catalyst in heterogeneous electro-Fenton (EF) process for the abatement of a biorefractory model dye pollutant, Acid Orange 7 (AO7). The complete degradation of 200 mL AO7 (0.1 mM) was achieved after 40 min contact with the modified material instead of more than 120 min with the pristine one. The proposed catalytic system exhibited an attractive activity with the total organic carbon (TOC) removal reaching 26.6 % after 8 hours at pH 6.5. The present results prove a promising efficiency of iron-rich MFI@CF material for a "green" EF treatment of water 2 pollutants, avoiding the use of any non-recyclable soluble Fe 2+ salt classically required as EF catalyst.

International audience; The degradation pathway of Acid Orange 7 (AO7) by Electro-Fenton process using carbon felt cathode was investigated via HPLC-UV and LC-MS, IC, TOC analysis and bioassays (Vibrio Fischeri 81.9% Microtox® screening tests). The TOC removal of AO7 reached 96.2% after 8 h treatment with the optimal applied current density at −8.3 mA cm−2 and 0.2 mM catalyst concentration. The toxicity of treated solution increased rapidly to its highest value at the early stage of electrolysis (several minutes), corresponding to the formation of intermediate poisonous aromatic compounds such as 1,2-naphthaquinone (NAPQ) and 1,4-benzoquinone (BZQ). Then, the subsequent formation of aliphatic short-chain carboxylic acids like acetic acid, formic acid, before the complete mineralization, leaded to a non-toxic solution after 270 min for 500 mL of AO7 (1 mM). Moreover, a quantitative analysis of inorganic ions (i.e. ammonium, nitrate, sulfate) produced during the course of degradation could help to verify molar balance with regard to original nitrogen and sulfur elements. To conclude, a clear degradation pathway of AO7 was proposed, and could further be applied to other persistent pharmaceuticals in aquatic environment.

Hierarchical three-dimensional (3D) porous architecture FeIIFeIII layered double hydroxide (LDH) multiwall was grown on carbon-felt (CF) substrate via solvothermal process. The as-deposited FeIIFeIII LDH/CF cathode was composed of highly oriented and well crystallized interconnected nanowalls with high electrical conductivity and excellent catalytic activity over a wide pH range (pH 3–9) for heterogeneous electro-Fenton (HEF) degradation of antibiotic sulfamethoxazole (SMT) in aqueous medium. Mineralization efficiencies (in terms of TOC removal) of ∼97%, 93% and 90% was achieved at pH 3, 6 and 9 respectively for FeIIFeIII cathode during HEF treatment of 0.2 mM SMT solution at applied current density of 7.5 mA cm−2 using Ti4O7 anode. Comparative electro-Fenton (EF-Fe2+) with 0.2 mM Fe2+ or electrooxidation with H2O2 production (EO-H2O2) studies using raw CF cathode at similar experimental conditions showed relatively lower mineralization with highest TOC removal efficiency of 77% and 64% obtained at pH 3 for EF-Fe2+ and EO-H2O2 respectively. Oxidative degradation of SMT in HEF system was by (i) Ti4O7( OH) generated at anode surface at all pH studied, (ii) surface catalyzed process and (iii) contribution from homogeneous catalyzed process at pH 3 due to leached iron ions. The prepared FeIIFeIII LDH/CF exhibited excellent catalytic stability with good reusability up to 10 cycles of 4 h treatment at pH 6. Initial SMT solution showed relatively high toxicity but total detoxification of the solution was attained after 8 h of treatment by HEF with FeIIFeIIILDH/CF cathode. HEF with FeIIFeIII LDH/CF cathode is an exciting technique for remediation of organic contaminated wastewater.

International audience

A new cathode for electro-Fenton process was set up by electrochemical deposition of reduced graphene oxide (rGO) on the surface of carbon felt (CF). The structure and properties of modified electrode was investigated. Among the different reduction methods used, the constant potential technique demonstrated significant advantages. The parameters affecting the conversion of GO to rGO, such as pH, applied potential and duration of the reduction process, were investigated. The rGO modified cathode presents enhanced electrochemical properties like an increase of the redox current and a decrease of the charge transfer resistance in presence of the redox probe [Fe(CN) 6 ] 3− /[Fe(CN) 6 ] 4− showing better kinetic properties compared to raw CF. This improvement enhanced significantly the production of hydrogen peroxide, a key parameter in electro-Fenton (EF) process, which was confirmed by linear scanning voltammetry (LSV) analysis. Therefore, the use of graphene modified cathode could decolorize efficiently Acid Orange 7, a model azo dye molecule, within only 5 min and almost completely mineralized (94.3%) it in 8 h treatment under optimal current density applied. The new cathode exhibited good stability as the mineralization ratio in 2 h that was still above 64% after 10 cycles’ degradation, showing that this rGO-CF is a powerful and promising electrode for improving the removal efficiency of dye pollutants using EF technology.

International audience; Carbonaceous materials are abundantly used for electrochemical applications and especially for energy and environmental purposes. In this review, the carbon felt (CF) basedelectrodes are discussed in a holistic manner. First of all, the study centers on the issues relevant to pristine CF materials such as manufacturing method and specific properties. The various methods and equations used to identify physical values of CF material are supplied. As main part of the review, the different modification methods for CF electrodes are described. The novel properties of fabricated materials are characterized by physical as well as electrochemical techniques. The strengths of each method are presented in the comparison with raw CFelectrodes. The energy applications of CF based-electrodes are figured out in various fields such as vanadium redox flow batteries (VRFB), microbial fuel cells (MFCs), biofuel cells (BFCs), capacitors, solar cells and lithium ion batteries. For environmental applications, we focus our study on the wastewater treatment containing biorefractory pollutants by electro-Fenton (EF)process. The degradation result by EF technology using CF materials is impressive when most of toxic contaminants are mineralized to non-toxic compounds at the end of the electrolysis. To decrease the cost treatment and upgrade the treatment efficiency, the EF system has been improved by using modified electrodes or new catalyst sources. The CF materials are also investigated to apply in bio-fuel cell-Fenton in which electrons were produced from fuel cell (FC)towards zero-energy depollution. Finally, the sketches about EF pilot open new gates for application of CF materials in industrial areas.

International audience; A novel material was fabricated by deposition of graphitized Nitrogen-doped Porous Carbon layer (NPC) on commercial Carbon Felt (CF). The NPC was obtained via Atomic Layer Deposition of zinc oxide (ZnO) and its subsequent solvothermal conversion to Zeolitic Imidazolate Framework (ZIF-8) followed by its carbonization under controlled atmosphere. Bothphysical and electrochemical properties have been evaluated by Scanning Electron Microscopy, X-Ray Diffraction, Energy-Dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, nitrogen sorption, contact angle and cyclic voltammetry measurements. The parameters affecting the growth of NPC, such as the amount of ZnO/ZIF-8 material before calcination and thermal treatment temperature have been investigated in details. The versatility of the as-prepared NPC/CF material was assessed by studying: i) its adsorption ability and/or ii) its behavior as cathode in Electro-Fenton process (EF) for the elimination of a model refractory pollutant (acid orange 7 (AO7)). Once used as adsorbent, the NPC/CF proved good adsorption 2capacity with 97 % color removal of initial 0.02 mM dye concentration after 30min. Moreover, the application of such novel cathode could also reduce the cost for EF technology by using lower energy consumption at 0.54 kWh g−1 TOC. The apparent rate constant (kapp~0.8 min-1) obtained for NPC/CF was more than 7 times higher compared to pristine CF commercial electrode, thus leading to more than 90% TOC removal in 8 h. In addition, high reaction efficiency and system durability were attributed to continuous regeneration of the NPC/CF sorption capacity upon total mineralization of the pollutants accumulated at the electrode surface. Results confirmed that the new NPC/CF material behaves as a highly active electrode with attractive adsorption efficiency and at the same time it possess an excellent electrochemical activity in Electro-Fenton (EF) oxidation process for the removal of persistent water pollutants.

Hierarchical CoFe-layered double hydroxide (CoFe–LDH) was grown on carbon felt (CF) as a heterogeneous catalyst by in situ solvothermal growth. The CoFe–LDH/CF serves as a cathode as well as a Fe2+ (catalyst) source in the electro-Fenton (EF) process. A combined structural and electrochemical characterization revealed highly ordered and well crystallized CoFe–LDH anisotropically grown on a CF substrate with highly dense urchin-like structures that were highly stable at circumneutral pH. EF experiments with the CoFe–LDH/CF cathode showed excellent mineralization of Acid Orange II (AO7) over a wide pH range (2–7.1). The mineralization of AO7 with CoFe–LDH/CF was by both homogeneous and surface-catalyzed processes at low acidic pH, whereas only the surface-catalyzed process occurs at circumneutral pH due to the stability of the LDH as well as precipitation of the catalyst. Higher mineralization was achieved with CoFe–LDH/CF compared to homogeneous EF with raw CF using the Fe2+/Co2+ catalyst at all pH values studied and the TOC removal with the CoFe–LDH/CF cathode was at least 1.7 and 3.5 times higher than that with the homogeneous system with Fe2+/Co2+ at pH 5.83 and 7.1, respectively. The enhanced performance observed with CoFe–LDH/CF was ascribed to (i) the surface-catalyzed reaction occurring at the surface of the cathode which can expand the working pH window, avoiding the precipitation of iron sludge as pH increases, (ii) enhanced generation of H2O2 due to the improved electroactive surface area of the cathode and (iii) the co-catalyst effect of the Co2+ in the LDH that can promote regeneration and additional production of Fe2+ and the hydroxyl radical, respectively. The CoFe–LDH/CF cathode exhibited relatively good reusability as the TOC removal after 2 h was still above 60% after 7 cycles of degradation, indicating that the prepared CoFe–LDH/CF is a promising cathode for the removal of organic pollutants by EF technology.

International audience; The evolution of the degradation by-products of an acetaminophen (ACE) solution was monitored by HPLC-UV/MS and IC in parallel with its ecotoxicity (Vibrio fischeri 81.9%, Microtox® screening tests) during electro-Fenton (EF) oxidation performed on carbon felt. The aromatic compounds 2-hydroxy-4-(N-acetyl) aminophenol, 1,4-benzoquinone, benzaldehyde and benzoic acid were identified as toxic sub-products during the first stage of the electrochemical treatment, whereas aliphatic short-chain carboxylic acids (oxalic, maleic, oxamic, formic, acetic and fumaric acids) and inorganic ions (ammonium and nitrate) were well identified as non-toxic terminal sub-products. Electrogenerated hydroxyl radicals then converted the eco-toxic and bio-refractory property of initial ACE molecule (500 mL, 1 mM) and subsequent aromatic sub-products into non-toxic compounds after 2 h of EF treatment. The toxicity of every intermediate produced during the mineralization of ACE was quantified, and a relationship was established between the degradation pathway of ACE and the global toxicity evolution of the solution. After 8 h of treatment, a total organic carbon removal of 86.9% could be reached for 0.1 mM ACE at applied current of 500 mA with 0.2 mM of Fe2+ used as catalyst.

In electro-Fenton process, carbon-based materials, particularly 3D carbon felt, are the best choices for the cathodic electrodes because of several advantages such as low cost, excellent electrolytic efficiency, high surface area, and porosity. In this chapter, various aspects of this material are discussed in detail. This chapter is divided into three main sections, including (1) characterization of carbon felt (CF), (2) modification of CF, and (3) application of CF in electro-Fenton (EF) process to remove biorefractory pollutants. First of all, the typical characteristics of CF such as morphology, porosity, and conductivity are discussed. Next, in the modification section, we introduce different methods to improve the performance of CF. We especially focus on the surface area and electrochemical activity toward electrodes applications. Finally, both modified and non-modified CF is used as cathode materials for EF systems like homogeneous, heterogeneous, hybrid, or pilot-scale types.

International audience; Metal hollow fibre membranes offer excellent chemical and mechanical stability and are promising platforms for the removal of harsh contaminants from solutions. Stainless steel (SS) membranes are however prone to oxidation and advanced decoration routes are required to passivate the surface of such materials. Here, SS membranes were modified with nanoscale coatings of graphene to promote electrochemical reactions and prevent premature corrosion of the bare metal reinforcement upon electro-Fenton (EF) reaction. Samples decorated with graphene oxide or reduced graphene oxide were compared to bare SS membranes to assess the impact of graphitization on the electrochemical performance of the membranes. Membranes properties were characterized using both cyclic and linear scanning voltammetry. The results evidenced that electron transfer kinetics were significantly enhanced on the reduced graphene oxide, compared to raw material. In addition, the removal efficiency of a pharmaceutical pollutant, paracetamol, was evaluated in electro-Fenton batch experiments, on the three membrane electrodes. The best mineralization current efficiency at 37% was found when using reduced graphene oxide membrane cathode at optimal applied potential of -0.5 V vs. SCE (Saturated Calomel Electrode). Finally, the coupling of electro-Fenton and filtration processes was carried out on a pilot-scale unit. Various electrochemical and hydrodynamic parameters that affect mineralization efficiency were studied. By coupling filtration and electrochemical processes, the mineralization current efficiency value was increased remarkably by 165% and remained stable for three consecutive cycles. This strategy opens up opportunities to generate low cost catalytic membrane reactors with high flux and selectivity from the materials reactivity as opposed to sieving, with potential for harsh chemicals mineralization.

International audience; A model azo dye pollutant, Acid Orange 7 (AO7), was removed efficiently from an aqueous medium by a smart eco-friendly Fuel Cell-Fenton (FC-Fenton) system without any external power supply. In this approach, AO7 was degraded by an electro-Fenton process at a designed cathode (Carbon Felt (CF)/porous Carbon (pC)) supplied by direct clean electrical energy from abiotic glucose oxidation at a CF/gold anode (CF@Au). The highly active cathode was fabricated by an attractive route combining Atomic Layer Deposition (ALD) of ZnO on commercial carbon felts (CFs) followed by subsequent solvothermal conversion of the metal oxide to a metal organic framework (here ZIF-8). The as-prepared composite material was further calcined at high temperature under a controlled atmosphere. A pC-based support with high specific surface area and nitrogen as a dopant was thus obtained, enhancing both conductivity and electrocatalytic properties toward H2O2 production from oxygen reduction. Degradation kinetics of AO7 (0.1 mM initial concentration) at the CF@pC cathode was monitored by UV-vis spectrophotometry and High-Performance Liquid Chromatography (HPLC) to prove the efficiency of the composite material for the degradation of such a bio-refractory model molecule. Benefitting from the H2O2 production rate (9.2 mg L−1 h−1) by the pC layer, AO7 (35.0 mg L−1) was degraded by the electro-Fenton process in acidic medium (pH = 3) with removal efficiency reaching 90% in 10 h. The durability of the system was extended for more than 2 months with an average power output of 170 mW m−2, confirming this abiotic FC-Fenton system as a promising, green, future technology for both environmental and energy-related areas, including membrane-coupled reactor systems.

International audience; In this study, homogeneously dispersed gold particles growth onto carbon felt were fabricated by electrodeposition method followed by a thermal treatment at 1000 °C under nitrogen. The thermal treatment induced the dewetting of gold and the formation of well-crystallized gold particles that exhibited large surface area. The structural properties of the resulted Au@CF material were evaluated by SEM, XRD and TGA. We studied the electrocatalytic properties of this new gold material through the abiotic glucose oxidation in alkaline medium and the enzymatic dioxygen electroreduction by the enzyme bilirubin oxidase. Finally, we showed the potentiality of the resulting Au@CF material to build a 3-dimensional glucose hybrid biofuel cell by assemblying an abiotic anode with an enzymatic cathode. The system exhibited high electrochemical performance with an open circuit voltage of 0.71 V and a maximum power density of 310 μW cm−2 at 352 mV (by taking into account the projected surface area), in spite of a low gold loading (0.2 wt%). The advance presented in this work is the efficiency of the synthesis technique to get a new free-standing material for electrocatalysis based on gold particles with high reactive surface area for electron transfer and macropores for diffusion transport

International audience; Porous carbon cathode (PCF) was fabricated by thermal treatment at high temperature under a nitrogen gas flow mixed with 1% of oxygen. Scanning electron microscopy results revealed a homogenous porosity covered the carbon fibres. This property improved significantly the hydrophilicity that supported the oxygen reduction reaction (ORR) in electro-Fenton process as confirmed by contact angle measurements. In addition, an increase of 700 times of the surface area is observed after the thermal treatment. The crystalline average size of the new material was also ameliorated during thermal treatment as observed by X-ray diffraction pattern (XRD) due to the selective etching of amorphous carbon. Porous cathode exhibited also better electrochemical performances than raw carbon felt cathode as proved by cyclic voltammograms (CVs) because of the higher electroactive surface area. According to the Randles-Sevcik formula, the electroactive surface area of PCF was 10 times higher than raw CF. The concentration of H2O2 on PCF and raw CF was 24.6, 7.9 mg L-1 respectively after 80 min. The porous cathode was applied for removal of paracetamol (PCM) in acidic aqueous medium using an electro-Fenton process. Mineralization of PCM was followed by total organic carbon (TOC) measurements and an improvement of 31% was observed compared to the non-modified cathode after 2 h of electrolysis. The porous carbon cathode kept its stability after 10 cycles.

Reduced Graphene Oxide (rGO) was coated on Carbon Felt (CF) in order to design a novel cathode applied in the Electro-Fenton (EF) reaction for decontamination of wastewater polluted with Persistent Organic Pollutants (POPs). The new cathode was fabricated by an electrophoretic deposition of Graphene Oxide (GO) followed by its electrochemical reduction at a current density of −1.5 mA cm−2 for 10 min. The modified electrode and GO were characterized by SEM, AFM, XRD and XPS, showing the presence of rGO after optimization of the electrochemical conditions of synthesis. Electrode modification has improved the CF electrochemical properties as proved by the decrease of the charge-transfer resistance (Rct) determined by electrochemical impedance spectroscopy (EIS) and the increase of the CV response (2.5 times) of the FeIII/FeII couple used as a redox probe. Degradation of Acid Orange 7 (AO7), a model pollutant molecule, was monitored by UV-Vis spectrophotometry at the selected single wavelength λ = 485 nm. The results show that the degradation kinetics were 2 times higher on the graphene modified cathode compared to raw carbon felt proving the efficiency of this modification process.

Oxide polypyrrole (PPy) composite films have been studied as protective coatings for iron. PPy films. containing strong oxidative species like oxide, have been obtained in order to maintain the polymer in its oxidized state which corresponds to the iror passive domain. Oxide particles in suspension in pyrrole/tetraoxalate solution have been embedded in PPy film during its electrodeposition. The films have been characterized by electrochemical quartz crystal microbalance, scanning electron microscopy, t-ansmission electron microscopy, and tested in 3% NaCI corrosive medium. A significant improvement of the protection efficiency was obtained with PPy/iron oxide composite films and especially with PPy/Fe 3 O 4 composite films.