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• Reduction of Au(III) via a 2e−+1e− path on GC but via a direct 3e− path on pt. • Comproportionation/disproportionation equilibrium of the Au(III)-Au(I)-Au(0) system. • Standard potentials of the involved redox couples were estimated. The electrochemistry of the Au(III)-Au(I)-Au(0) system was studied in the choline chloride - oxalic acid dihydrate deep eutectic solvent at 60 °C. At glassy carbon electrodes, the 2 e− waves of the Au(III)/Au(I) and the 1 e− waves of the Au(I)/Au(0) are well separated in the cyclic voltammograms, whereas at platinum electrodes two anodic peaks but only one single 3 e− cathodic peak are observed. Electrochemical quartz crystal microbalance and zero-current chronopotentiometric experiments demonstrate the occurrence of a comproportionation reaction AuCl 4 − + 2 Au (0) + 2 C l − ⇌ 3 AuCl 2 − when gold is electrodeposited from an Au(III) solutions. The standard potentials of the Au(III)/Au(I), Au(I)/Au(0) and Au(III)/Au(0) couples were estimated, and even though E Au (III) / Au (I) 0 < E Au (I) / Au (0) 0 translates into an equilibrium constant of the reaction being unfavourable to the comproportionation (K c,comp < 1), it is shown that the reaction can be quantitatively displaced to the right under non-equilibrium conditions imposed by mass-transport. [ABSTRACT FROM AUTHOR]

Two-step aluminium anodizing is widely used to prepare oxide films with a highly-ordered porous structure through the whole thickness. It can be realized solely at relatively low values of current density in the kinetic anodizing regime that makes this process extremely time-consuming. Temperature is an important thermodynamic parameter which is able to accelerate chemical reactions and mass-transport and, thus, could be suggested as an effective tool to control the growth rate of anodic alumina. Here we report a systematic study of the porous anodic alumina films formation in 0.3 M oxalic acid electrolyte in a wide temperature range. The influence of electrolyte temperature on the kinetics of aluminium anodizing and on the morphology of the obtained anodic alumina films is addressed quantitatively. Current transients registered at various temperatures are used for the calculation of the apparent activation energy of the anodization process in both mild and hard anodizing regimes. In the case of thick oxide films and high electrolyte temperature, the increase in diffusion current contribution leads to switching the kinetically controlled anodizing to the mixed regime which results in destroying the hexagonal pore ordering. Based on the experimental findings, rational electrolyte temperatures and porous layer thicknesses for the first and second anodizing steps are proposed as a guide for express preparation of alumina films with well-ordered porous structure. Image 1 • Anodizing of Al in a wide range of electrolyte temperature is systematically studied. • Activation energy of Al anodizing in kinetic regime is higher than in diffusion regime. • Pore ordering degree in thin AAO films does not decrease with electrolyte temperature. • Diffusion controlled regime is not sufficient for self-ordering of porous structure. [ABSTRACT FROM AUTHOR]

• PANI nanosheets are prepared through a separation-free templating method. • Aniline–acid precipitates serve as the templates for producing PANI nanosheets. • The properties of the polyaniline can be tuned by controlling the aniline/APS ratio. • PANI nanosheets-based flexible SCs show superior low-temperature performance. The simple synthesis of two-dimensional (2D) polyaniline (PANI) structures remains a big challenge owing to the intrinsic growth of PANI chains into one-dimensional structures and the curling of the PANI chains into spherical particles. In this contribution, we report on the simple synthesis of PANI nanosheets by oxidizing aniline–acid precipitates with ammonium persulfate (APS) through a chemical oxidation polymerization method. The tested acids include methylene disulfonic acid, sulfuric acid, benzoic acid, oxalic acid, p -toluenesulfonic acid, hydrochloric acid, and acetic acid. The aniline–acid precipitates serve as separation-free templates for producing PANI nanosheets. The yield, oxidation level, electronic conductivity, conjugation length, and thickness of the PANI nanosheets can be tuned by controlling the molar ratio of aniline/APS. The electrochemical performance of PANI nanosheets-based symmetric supercapacitors was examined at the temperature ranging from room temperature to –60 °C. The PANI nanosheets with relatively high specific surface area rather than the oxidation level manifest superior electrochemical performance. Polyaniline nanosheets templated from aniline–acid precipitates do not experience a phenazine heterocycling mechanism and show superior electrochemical performance for flexible supercapacitor. [Display omitted] [ABSTRACT FROM AUTHOR]

Many theoretical and experimental studies have been focused on the physicochemical properties of dense ionic fluids such as ionic liquids (ILs). However, less attention has been given to interfacial properties involving deep eutectic solvents (DES). The impact of the DES composition, hydrogen bond donor (HBD) structure, temperature, and electrode nature material on the DES-electrode vertical interactions remain vague. The lack of knowledge imposes significant constraints in proposing a suitable Electrical Double Layer model (EDL) to describe the DES at electrified interfaces. Measuring differential capacitance-potential curves is a strategy to assess the EDL structure and understand how ions interact with the electrode surface, which knowledge is fundamental to designing and optimizing electrochemical systems for various applications (e.g. , energy storage devices). Accordingly, a set of choline chloride-based DESs was assessed containing distinct HBD at their eutectic composition (the polyalcohol's 1,2-ethanediol, 1,2-propylene glycol, 1,3-propylene glycol, and the amide urea) against glassy carbon (GC), gold (Au), and the platinum (Pt) electrode at different temperatures. The differential capacitance-potential curves were found to vary significantly in shape in the three different electrode surfaces studied, ranging from camel shape (Au electrode), U-shape (GC), and asymmetric bell shape (polycrystalline Pt). The carboxylic malonic and oxalic acids were also assessed for a proper comparison to understand better the role of the HBD's functional group in shaping the electrode-electrolyte structure against the trend found with diol isomers. A suitable EDL model must inevitably accommodate interfacial properties assessed at the capacitive region, namely the influence of the surface chemistry, potential dependence, DES structure molecules, and temperature in shaping the electrified interfacial anatomy. [ABSTRACT FROM AUTHOR]

Porous-anodic-alumina (PAA)-assisted anodizing in oxalic acid electrolytes combined with re-anodizing to a more anodic potential of a titanium layer on substrate, followed by chemical dissolution of the PAA overlayer result in TiO 2 nanocolumn arrays, which may however be chemically unstable and destroy during the PAA dissolution. Here we show that this is because the TiO 2 nanocolumns have easy-to-dissolve alumina-titania mixed-oxide ‘nanoroots’ penetrating the alumina barrier layer, where gas nano-bubbles and voids form respectively inside and between the titania roots, owing to the field-assisted crystallization of the bottom titanium oxide. The problem is solved by alloying nitrogen with titanium in the precursor film, with a compositional spread of nitrogen from 2 to 50 at%, to grow differently N-doped TiO 2 nanocolumn arrays via the PAA-assisted anodizing in oxalic acid at 40 V followed by re-anodizing up to 240 V. The stability of such arrays increases with increasing nitrogen content, reaching an ideal 100% level for the Ti–50 at%N alloy films. The effect is proved to be due to the incorporation of nitrogen into the columns and roots with formation of oxynitride, which increases their chemical resistance and effectively suppresses the field-assisted crystallization of titania, leading to the obstructed O 2 evolution, smaller bubbles and voids, less mixing of the two oxides in the roots, and thickening and merging the roots. A model is developed of the oxide growth and dissolution, explaining the instability of the pure TiO 2 nanocolumn arrays and defining the stabilizing effect of the nitrogen species. The doping with nitrogen may make the TiO 2 nanocolumn arrays highly appropriate for applications to photocatalysis and energy conversion. [ABSTRACT FROM AUTHOR]

• Operando capacity recovery method was proposed. • VO 2 + electroreduction in electrolysis cell is efficient and fast. • Chemical regeneration was carried out via VO 2 + reduction by oxalic acid. • VO2+ regeneration is fast and can be performed at room temperature. • The capacity recovery is efficient and stable under VRFB cycling conditions. Gradual capacity fade of vanadium redox flow batteries (VRFB) is one of the greatest challenges for further distribution of this technology, since capacity stability is crucial for industrial energy storages. It is suggested that the main reason for this issue is vanadium ions crossover, however recent studies show that appearance of chemical and electrochemical side reactions leading to increase of the electrolyte average oxidation state (AOS) should be considered as a greater contributor to capacity fade. It should be noted that increase of overall AOS is more challenging to eliminate compared to vanadium ions crossover. To date, a great variety of VRFB capacity fade mitigation methods have been proposed, but very little attention has been paid to development of methods for the battery capacity recovery. Despite several methods for AOS decreasing via partial posolyte reduction have been demonstrated, none of them were implemented for operando capacity recovery due to a number of ongoing issues. In this work, a novel method for operando VRFB capacity is proposed. It consists of partial electroreduction of posolyte in electrolysis cell utilizing chemically regenerative electrolyte. Regeneration of VO2+ by reducing agents is cost-effective, and separation of this process from the battery using electrolysis cell allows proceeding VRFB capacity recovery operando. This study is devoted to investigation of both chemical and electrochemical stages of the proposed method, and its optimization for rebalancing under cycling conditions. It is suggested that integration of the VRFB stack with the proposed rebalancing system allows to demonstrate high battery performance while maintaining nominal capacity indefinitely. [ABSTRACT FROM AUTHOR]

This paper presents research on modifying the surface of Ti-15Mo alloy using electropolishing and anodic passivation. The electropolishing process was carried out in solutions containing sulfuric acid, ethylene glycol, ammonium fluoride and oxalic acid. Whereas a voltage range from 20 to 100 V and a 1 M orthophosphoric acid solution were used during the anodic passivation. The influence of above mentioned processes parameters on the quality of the obtained oxide layer on Ti-15Mo alloy was investigated. The analysis of Ti-15Mo surface after modification was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), ellipsometry, and mechanical tests. Moreover, the corrosion resistance was investigated using a potentiostatic method in Ringer’s solution. It was found that electropolishing leads to an increase in the surface homogeneity and to the form of an oxide layer, which consisted of TiO 2 and MoO 3 . Whereas the oxide layers obtained during anodic passivation were characterized by different properties depending on the applied voltage. The anodic passivation at various voltages (20–100 V) increased the surface wettability (94.5°–87.6°) in comparison to the electropolished sample (97.5°). Moreover, the obtained oxide layer after anodization exhibited a high hardness. The electrolytic polishing and anodic passivation of Ti-15Mo also improved corrosion resistance of the alloy in contact with Ringer's solution. The sample anodized at 80 V presented the highest corrosion resistance by the smallest corrosion current density (1.4 nA cm −2 ) and the highest polarization resistance (37.4 MΩ cm 2 ). [ABSTRACT FROM AUTHOR]

Nanoporous tin oxide layers were obtained by one-step potentiostatic anodization carried out in 0.3 M H 2 C 2 O 4 followed by thermal annealing at temperatures in the range of 200–700 °C. The morphology and crystallinity of as obtained oxide layers were characterized by SEM, and XRD, respectively. It was confirmed, that after 10 min of anodic oxidation at the potential of 8 V, anodic tin oxide consists of a dense array of randomly distributed nanopores with an average diameter of about 50–60 nm. Moreover, such kind of porous structures is maintained during annealing at temperatures up to 500 °C. On the contrary, for higher annealing temperatures a transformation of nanoporous layers into particle-like structures was evident. A gradual increase of the crystallite size with increasing annealing temperature was also confirmed. Finally, photoelectrochemical properties of anodic tin oxide layers, annealed at temperatures in the range of 400–700 °C, were extensively investigated. The best photoelectrochemical performance with the maximum photocurrent densities of above 25 μA cm −2 and conversion efficiency of about 30% was observed for sample annealed at 500 °C. Higher annealing temperatures result in a gradual decrease in photocurrent densities that can be attributed to the change in the sample morphology and decrease in electrochemical reaction sites. Optical band gap energies were determined on the basis of UV–vis reflectance spectra and photocurrent measurements, and a gradual increase in the band gap energy with increasing annealing temperature was confirmed. [ABSTRACT FROM AUTHOR]

The aim of this work was to verify if the quality, regularity and spacing of nanoconcaves formed on the Al surface during the first step of anodization (pre-texturing) have a significant effect on the morphology of AAO layers grown during the second anodization continued at the same potential but in different electrolytes. High purity (99.999%) aluminum substrates were anodized at 25 V and 45 V in sulfuric acid and oxalic acid, respectively. After chemical etching of initially formed oxide in a mixture of chromic and phosphoric acid, the samples were re-anodized under the same potentials, but in different electrolytes (sulfuric, oxalic, phosphoric acids). It was confirmed that the regular nanoporous structure formed on the Al surface during the first anodizing step is initially replicated at the beginning of the second anodization, independently of the electrolyte used. However, these initially formed oxide layers exhibit significantly different pore diameters but the same pore spacing, which is determined by the cell spacing on the Al surface. When phosphoric acid is used as an electrolyte, the prolonged anodization resulted in the formation of typical serrated nanochannels. However, we successfully obtained the almost ideally-ordered porous anodic alumina layer with a thickness of about 700 nm, and the average diameter of nanochannels of ∼50 nm after the second anodization carried out for 20 min at 45 V in 0.3 M H 3 PO 4 , outside from the self-ordering regime for this electrolyte. [ABSTRACT FROM AUTHOR]

Three dimensional (3D) kesterite Cu 2 ZnSnS 4 (CZTS) is synthesized by a facile solvothermal method using oxalic acid (OA) as additive agent. The as-synthesized CZTS samples are further annealed at 400 °C in argon atmosphere to obtain the expected samples. The structure and morphology of the expected samples are characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) technique. The results show that the Cu 2 ZnSnS 4 takes on morphology of microspheres with ultrathin nanosheet constituents and has a stoichiometric composition. As a novel anode material for the lithium-ion batteries (LIBs), the as-prepared CZTS microstructures exhibit both high reversible capacity and good cycling performance at room temperature under a potential window from 3.0 to 0.01 V (vs. Li + /Li) at current density of 100 mAg −1 . The achieved initial discharge capacity is 1125 mAhg −1 and retained at 786 mAhg −1 after 100 cycles, which suggests that the kesterite CZTS can be a promising candidate as a novel anode material for the lithium-ion battery. [ABSTRACT FROM AUTHOR]

Binder-free NiO@MnO 2 core-shell structure was deposited on Ni foam used as electrode of supercapacitor. The rod-like NiO core was prepared by thermal decomposition of NiC 2 O 4 synthesized by corrosion of Ni foam with oxalic acid under hydrothermal conditions. Sphere-like MnO 2 shell was deposited on the surface of NiO core through hydrothermal treatment with KMnO 4 solution. The structure, composition, morphology evolution and surface chemical state of the NiO@MnO 2 electrode were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The obtained NiO and NiO@MnO 2 electrodes were directly used as electrodes of supercapacitor, and their electrochemical performances were tested with cyclic voltammograms, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The results show that the sphere-like MnO 2 shell leads to an impressive enhancement of the performance including the areal capacitance (AC) and cycling stability, particular in the AC. To be more specific, the NiO@MnO 2 exhibits a high AC of 3.584 F/cm 2 at a current density of 5 mA/cm 2 , which is much higher than that of NiO electrode whose AC is 1.483 F/cm 2 at the same current density, demonstrating the potential to use NiO@MnO 2 electrode for supercapacitor. At the same time, the related mechanisms for the superior performance were also discussed. [ABSTRACT FROM AUTHOR]

• A series of quinary oxalates (FeCoNiCuZn)(C 2 O 4)·2H 2 O were fabricated for the first time. • The prepared multi-metal oxalates exhibit large specific surface, diverse active site and good electronic coordination capabilities to provide great potential for efficient electrode materials. • This regulated solvent strategy enables the prepared 2D (FeCoNiCuZn)(C 2 O 4)·2H 2 O with superior activity and durable stability in both supercapacitors and OER performance. Design and fabrication of 2D multi-metal oxalate materials with desired electrochemical activities are highly needed in electrocatalysis and supercapacitors. Herein, assisted by the deep eutectic solvothermal (DES) method, multi-metal oxalate consisting of Fe, Co, Ni, Cu, and Zn with different morphology was the controlled synthesis. It was found that the structure and composition of DES can control the nucleation and growth of multi-metal oxalate. High molecular PEG and gradually slow-release oxalic acid are in favor of the formation of 2D structure, while the low molecular EG and abundant oxalic acid are positive for the formation of 3D nanoparticles. The properties of the obtained multi-metal oxalates are confirmed by multi-analysis, which involves the single Ni-oxalate phase, morphological evolution ranging from particles to nanosheets, and complex composition up to five metal elements including Fe, Co, Ni, Cu as well as Zn. Notably, the well-designed 2D (FeCoNiCuZn)(C 2 O 4)·2H 2 O nanosheets exhibit an ultralow overpotential of 334 mV at 100 mA cm−2 for OER as electrocatalyst with prolonged durability over 30 h at 10 mA cm−2 and a high specific capacity of 1337 C g−1 for aqueous supercapacitor. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we evaluated the effectiveness of the solar-powered electrokinetic process for the remediation of As-contaminated soil in order to reduce the electrical energy consumption on a pilot scale, and this study also investigated the influence of oxalic acid for the treatment of As bound to amorphous iron-oxide. The soil was collected from a former refinery plant located in Janghang, Chungnam, Republic of Korea. The experiments were designed two different power supply systems: a normal power supply and a solar-powered system, and operated the experiments for five weeks. The normal direct current (DC)-powered system removed 32% of the As, but the solar-powered system removed 27% of the As from the soil over the five weeks of electrokinetic operation. The energy expenditure of the solar-based system was just 50% of that of the DC-powered system. The results show that the solar-powered electrokinetic process can remove slightly smaller amounts of contaminants with much less electrical energy. Based on these results, the solar-based electrokinetic process could be applied in order to remediate As-contaminated soil. However, enhanced As removal should be achieved for actual application. [ABSTRACT FROM AUTHOR]

The free-standing through-hole porous alumina membranes (PAMs) were fabricated by two-step self-organized anodization of aluminum in oxalic acid followed by the subsequent voltage pulse detachment performed in an environmental-friendly solution based on HClO 4 and C 2 H 5 OH. The effects of oxalic acid concentration used for anodic oxide synthesis and the chemical composition of the barrier oxide layer on the effective detachment of PAMs were studied. On the other hand, the voltage detachment conditions such as applied voltage, number of pulses, and temperature of electrolyte were tested as parameters which might affect the detachment of PAMs and their bottom side morphology. It was found that the voltage detachment process is affected by applied detachment voltage while the bottom surface morphology of detached PAMs is influenced by oxalic acid concentration used for anodization, the chemical composition of the barrier oxide layer, and the time gap between anodization and detachment (storage period). Furthermore, it was revealed that number of applied pulses and electrolyte temperature maintained during the detachment have a little effect on the morphology of PAM films. The most feasible and detailed mechanism of the voltage pulse detachment, considering the individual stages of the process, was proposed. At the beginning, the mechanism was related to an electric field assisted dissolution of oxide enhanced by its chemical dissolution induced by Joule's heating. These processes occur at the pore bottoms upon application of the voltage pulse and results in pore widening and thinning of the barrier layer. Then, after the electrical breakdown of the barrier layer, the intensive electropolishing of aluminum at the metal/oxide interface takes place. [ABSTRACT FROM AUTHOR]

Bromoform (BF) is a stable and carcinogenic contaminant in water. In this study, efficient debromination and decomposition of BF induced by contact glow discharge electrolysis (CGDE) in a sodium sulfate solution were investigated. Intermediate byproducts were determined by ionic chromatography and gas chromatography, respectively. Experimental results showed that alkaline conditions and additions of organic additives to the solution were favorable for both the removal and the debromination of BF. Oxalic acid, formic acid, dibromomethane and bromate ion were determined as the major intermediate byproducts. Final products were inorganic carbon and bromide ion. Hydrated electrons may be the most likely active species responsible for the initiation of the debromination, and hydroxyl radicals may be the ones for the oxidation of the intermediate byproducts. [ABSTRACT FROM AUTHOR]

Oxalic acid etching and hydrogen treatment were applied on Ti substrates of IrO 2 –Ta 2 O 5 coated anodes. The coatings were prepared by thermal decomposition of a mixture of H 2 IrCl 6 ·6H 2 O dissolved in hydrochloric acid and TaCl 5 dissolved in alcohol. Surface morphology, microstructure, matter phase, electrochemical properties and accelerated life of the anodes were observed and examined. Compared with the anode without its substrate treated, the anodes with the substrates oxalic acid etched and hydrogen treated at 300 °C, 400 °C, 500 °C and 600 °C respectively show better electro-catalytic performance and longer life. However, effects of two methods are different. Oxalic acid etching of the substrate, which could get better improvement at accelerated life, while hydrogen treatment of the substrates, which could get better improvement at the electro-catalytic performance. Especially, anode with 400 °C hydrogen treated substrate has the highest electro-catalytic activity. [ABSTRACT FROM AUTHOR]

Luminescence during a constant current electrolytic oxidation of tantalum in phosphoric acid and oxalic acid is investigated. Weak anodic luminescence (galvanoluminescence) of barrier oxide films during the electrolytic oxidation is correlated to the existence of surface imperfections. Galvanoluminescence is more intense for rougher tantalum samples, higher current density, and higher electrolyte temperature. Spectral characterization of galvanoluminescence showed that there are wide luminescence bands mostly in the visible and near infrared spectral region. Small sized sparks generated by dielectric breakdown cause rapidly increasing luminescence intensity. The luminescence spectrum under spark discharging has several intensive peaks caused by electronic transitions in oxygen and hydrogen atoms. [ABSTRACT FROM AUTHOR]

Well-defined LiNi 0.5 Mn 1.5 O 4 powder has been synthesized by ethylene glycol (EG)-assisted oxalic acid co-precipitation method. The structure and physicochemical properties of this as-prepared powder were investigated by powder X-ray diffraction (XRD), Raman spectra (RS), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge test in detail. XRD shows impurity phase of Li y Ni 1-y O due to the oxygen loss reaction at high temperatures. SEM indicates that LiNi 0.5 Mn 1.5 O 4 synthesized by EG-assisted method has a uniform and narrow size distribution under 1 μm. RS confirms that both samples have Fd-3 m space group. EIS and CV test exhibit that LiNi 0.5 Mn 1.5 O 4 electrode synthesized by EG-assisted method has lower potential polarization, smaller charge transfer resistance, higher reversibility and larger lithium ion diffusion coefficient than the one obtained by ammonium hydroxide co-precipitation method. Galvanostatic charge–discharge test reveals that LiNi 0.5 Mn 1.5 O 4 synthesized by EG-assisted method shows higher discharge capacity than that the one synthesized by ammonium hydroxide co-precipitation method at each rate. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of the electrical discharges parameters during spark anodization of metallic Zr under galvanostatic regime have been investigated by image analysis in phosphoric and oxalic acid electrolytes. The experiments were recorder using a high-speed video camera during the entire anodization with a resolution of 1.7ms for determination of discharge lifetime and a standard resolution of 33ms (real-time imaging) for determination of the average area and discharge population density. The discharge behavior was dependent of the current density, electrolyte composition and anodization time. During breakdown process, sparks discharges are progressively turned to micro-arcs, which can be seen by enlargement of discharge area, gradual increase of lifetime and reduction of discharge population density. A factorial design was used to estimate the effects of experimental conditions on the discharge behavior. The current density and electrolyte composition were the most important factors that affected the discharge population density. The anodization time and the electrolyte composition were the main factor that influenced the discharge area and lifetime. In comparison with the voltage vs. time curve, the results demonstrate important features of the process and the changes of the electrical discharges characteristics during the experiments. [Copyright &y& Elsevier]

Abstract: Carbon coated triclinic LiVPO4F samples are synthesized by annealing the precursor obtained through a soft chemical route with mechanical activation assist. The V(+5) is reduced to V(+3) by oxalic acid dehydrate during ball milling process, and green slurry of amorphous Li–V–PO4–F is obtained. When the temperature rises to 550°C, the precursor starts crystallizing and good crystal of pure-phase LiVPO4F can be obtained at 550–650°C. But Li3V2(PO4)3 impurity is observed in samples fired at temperature above 700°C because of the volatilization of HF gas in the presence of moisture at high temperature. Charge–discharge tests show that the sample sintered at 700°C exhibits the best electrochemical performance, delivering the initial discharge capacity of 136 at 0.1C rate and 123mAhg−1 at 1C rate. Even at 5C rate, the discharge capacity remains 107mAhg−1 and keeps 95.3% after 100 cycles. EIS analysis shows that it possesses smaller impedance than other samples. The apparent chemical coefficient of lithium ions in the prepared sample is evaluated by cyclic voltammetry. [Copyright &y& Elsevier]

Abstract: In this study, a novel single-ion conducting polymer electrolyte, lithium polyvinyl alcohol oxalate borate (LiPVAOB), from the reaction of poly(vinyl alcohol) (PVA) with different molar ratio of boric acid, oxalic acid and lithium carbonate was prepared. The prepared materials were characterized by Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG), differential thermal analysis (DTA), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry. Ionic conductivity of these polymer electrolytes from adding an assistant (about 20wt.% propylene carbonate) is dependent on molar ratio of the reactants and can up to 6.11×10−6 Scm−1 at ambient temperature. Their electrochemical window can be stable up to 7V (vs. Li+/Li), which is of great attraction for high voltage lithium ion batteries with high energy density. [Copyright &y& Elsevier]

Abstract: In this paper, we have presented our recent investigation of luminescence during the anodization of zirconium in oxalic acid and 12-tungstosilicic acid water solutions. For the first time we have measured weak anodic luminescence (galvanoluminescence GL) during the anodization of zirconium and found strong influence of sample surface pretreatment, as well as of the current density, on luminescence intensity. Increased roughness of zirconium samples and higher anodization current density result in more intense GL. Spectral characterization of GL showed that there are wide GL bands present mostly in the range from 400nm to 825nm. As the anodization voltage approaches the breakdown voltage (about 380V in oxalic acid and 480V in 12-tungstosilicic acid), a large number of microdischarges appear superimposed on the GL. XRD and EDX measurements show that the main elements of the coating formed in oxalic acid are Zr and O, with ZrO2 as dominant crystalline phase. The main elements of the coating formed by PEO process in 12-tungstosilicic acid are Zr, O, and W. The coating is partly crystallized and mainly composed of ZrO2 and WO3. The elements present in PEO microdischares indicate that plasma is generated in microchannels filled with anodic gas with water vapor during the anodization of zirconium in 12-tungstosilicic acid. During PEO in oxalic acid additional zirconium plasma is generated in micro channels across the oxide layer. [Copyright &y& Elsevier]

Abstract: Several studies in the literature have investigated the electrochemical effects of oxalic acid and hydrazine on various materials in neutral (pH buffered to 7), basic or weakly acidic media (pH 6). The present work proposes electrochemical techniques that allow for the study of the electrochemical behavior, on a Pt electrode, of oxalic acid and hydrazinium nitrate to better understand their oxidation mechanisms in a nitric acid medium at a pH below 1; in addition, some experiments were carried out to define an electrochemical method that would allow for the simultaneous detection of these species when present within process effluent in very acidic solutions. Some physical data regarding oxalic acid and hydrazinium nitrate were also determined: anodic oxidation of hydrazinium nitrate and oxalic acid were observed at 0.2V and 0.7V (vs. Ag/AgCl), respectively. The diffusion coefficients of hydrazinium nitrate and oxalic acid were found to be 5.2×10−6 and 2.9×10−7 cm2 s−1, respectively. An experimental design approach demonstrated the influence of nitric acid concentrations on the diffusion coefficients of these species. [Copyright &y& Elsevier]

Abstract: The electrochemical oxidation of oxalic and oxamic acids on multiwalled carbon nanotubes (CNT) and on monometallic (Pd and Pt) and bimetallic (Pd–Cu, Pt–Cu) catalysts supported on multiwalled carbon nanotubes was investigated using cyclic voltammetry. The electrodes were prepared by dispersion of the catalytic material on Toray carbon (CT) using a Nafion/water solution. The kinetic parameters of the reactions were determined using cyclic voltammetry. Modification of Toray carbon electrode with carbon nanotubes enables the oxidation of oxalic and oxamic acids in the solvent stability region. The highest oxidation current densities were observed for the Pt–Cu/CNT/CT electrode in 0.1M NaCl. The oxidation potentials for both oxalic and oxamic acids in this case were lower than those observed with the CNT/CT electrode. The prepared electrocatalysts show good mechanical and chemical stability. [Copyright &y& Elsevier]

Abstract: This study investigated the anodization of tin in oxalic acid electrolyte at low applied voltages of U ≤5V. Under such conditions, the anodization product consists of micron-sized SnC2O4 crystalline particles and the morphology of the product changes during the anodization process in three distinctive stages. In the initial stage I, Sn dissolves into the electrolyte at high current density. This process is associated with the precipitation of highly oriented SnC2O4 crystals on the Sn surface. Stage II is a passivation process associated with the formation of a SnC2O4 surface layer with unique pyramidal microstructure via in situ conversion. Stage III is the localized creation of smaller SnC2O4 polyhedron crystals. The anodic reaction mechanisms for each stage are discussed in detail and a mathematical model is established to quantify the critical condition that induces the anodic passivation. [Copyright &y& Elsevier]

Abstract: The formation of porous anodic alumina in 0.4M oxalic acid is investigated over a range of current density and electrolyte temperature using sputtering-deposited substrates containing tungsten tracer layers. The findings reveal volume expansion factors and efficiencies of film growth that increase with the increase of the current density and decrease of the temperature. Pore generation by the flow of the anodic alumina in the barrier layer toward the pore walls is proposed to dominate at relatively high current densities (above ∼2mAcm−2), with tungsten tracer species being retained within films. Conversely, losses of tungsten species occur at lower current densities, possibly due to increased field-assisted ejection of Al3+ ions and/or field-assisted dissolution of the anodic alumina. [Copyright &y& Elsevier]

Abstract: Focused ion beam (FIB) patterning in combination with anodization has shown great promise in creating unique pore patterns. This work is aimed to understand the effect of the FIB patterned sites in guiding anodized pore development. Highly ordered porous anodic alumina has been created with the guidance of FIB created patterns on electropolished aluminum followed by oxalic acid anodization. Shallow concaves created by the FIB with only 1.5nm depth can effectively guide the growth of ordered nanopore patterns. With the guidance of the FIB pattern, the anodization rate is much faster and the nanopore growth direction bends at the boundary of the FIB patterned and un-patterned regions. FIB patterning also enlarges the anodization window; ordered nanopore arrays with 150nm interpore distances can be produced under an applied potential from 50V to 80V. The fundamental understanding of these unique processes is discussed. [Copyright &y& Elsevier]

Abstract: A facile hydrothermal method is developed to prepare rutile titania sub-microflowers consisting of nanorods with oxalic acid and TiOSO4 as reagents. The diameter of sub-microflowers and nanorods is found to be ca. 800 and 40nm, respectively. Also, the shape and size of building blocks in rutile titania sub-microflowers can be considerably controlled via adjusting the reaction time and reactant amounts. Rutile titania sub-microflowers composed of nanorods display higher discharge capacity and better rate cycle stability than other rutile titania nanostructures as lithium-ion battery anode material due to enhancing the Li-ion transfer rate for small size building blocks. [Copyright &y& Elsevier]

Abstract: The paper reports a systematic study concerning the role played by different organic compounds (glycolic acid, oxalic acid, glycerol) on the electrochemical oxidation process of aluminium in sulphuric acid solution. The result of the experiment as a whole provides a clear indication of the deep influence exerted by the three selected organic compounds on the aluminium oxide structure, leading to the formation of a more compact oxide layer. Electrochemical impedance spectroscopy results appear of particular interest; they are discussed in the light of a model proposed by Bojinov. The relevant parameters, half-jump distance a and cross-capture section S, are found consistently related to variations in the oxide structure (porosity). This gives a sounder basis to the physically correct nature of the assumptions underlying the Bojinov model, also suggesting that organic compounds are adsorbed at the aluminium oxide/aqueous solution interface. [Copyright &y& Elsevier]

Abstract: Electrosynthesis of polyaniline–molybdate (PANI–MoO4 2−) on mild steel was achieved in oxalic acid medium using cyclic voltammetry technique. Adherent and homogeneous PANI–MoO4 2− coating was obtained. The corrosion behavior of steel with PANI–MoO4 2− coatings in 1% NaCl solutions was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The coating was characterized by SEM, XPS, EDAX and FTIR. The self-healing ability of PANI–MoO4 2− coating was confirmed by SVET technique. It has been found that the PANI–MoO4 2− coating is able to offer higher corrosion protection in comparison to that of pure PANI coating due to inhibitive nature of molybdate ions. [Copyright &y& Elsevier]

Abstract: The mesoporous carbon ceramics SiO2/20wt% C (S BET =160m2 g−1) and SiO2/50wt% C (S BET =170m2 g−1), where C is graphite, were prepared by the sol–gel method. Scanning electron microscopy images and the respective element mapping showed that, within the magnification used, no phase segregation was detectable. The materials containing 20 and 50wt% of C presented electric conductivities of 9.2×10−5 and 0.49Scm−1, respectively. These materials were used as matrices to support cobalt phthalocyanine (CoPc), prepared in situ on their surfaces, to assure homogeneous dispersion of the electroactive complex in the pores of both matrices. The surface densities of cobalt phthalocyanine on both matrix surfaces were 0.014molcm−2 and 0.015molcm−2 for materials containing 20 and 50wt% of C, respectively. Pressed disk electrodes made with SiO2/50wt% C/CoPc and SiO2/20wt% C/CoPc were tested as sensors for oxalic acid. The electrode was chemically very stable and presented very high sensitivity for this analyte, with a limit of detection, LOD=5.8×10−7 molL−1. [Copyright &y& Elsevier]

Abstract: Ordered arrays of anodic alumina nanopores with uniform pore diameters have been fabricated by self-organized anodization of aluminum. However, gradient or alternating diameter nanopore arrays with designed interpore distances have not been possible. In this study, focused ion beam lithography is used to fabricate hexagonally arranged concaves with different diameters in designed arrangements on aluminum surfaces. The patterns are then used to guide the further growth of alumina nanopores in the subsequent oxalic acid anodization. Gradient and alternating nanopore arrangements have been attained by FIB patterning guided oxalic acid anodization. The fundamental understanding of the process is discussed. [Copyright &y& Elsevier]

Abstract: The carbon coated monoclinic Li3V2(PO4)3 (LVP/C) cathode materials are synthesized via a sol–gel method using oxalic acid as a chelating reagent and maltose as a carbon source. The effect of carbon content on the synthesis of LVP/C composites is investigated using X-ray diffraction, scanning electron microscopy, galvanostatic charge/discharge and DC resistance measurements. The results show that, among the LVP/C powders with different carbon content (5.7, 9.6, 11.6 and 15.3wt.%), the sample with 11.6wt.% carbon content gives rise to the corresponding (LVP/C) ∥Li half cell with a low DC resistance and superior electrochemical performance, especially with excellent rate capability. Its discharge capacity decreases by only 7.2% from 125mAhg−1 at 0.5C to 116mAhg−1 at 5C between 3.0 and 4.3V. The maltose-based sol–gel method is feasible for the preparation of LVP/C composites for high power lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: The nanopore arrays were fabricated by two-step self-organized anodization of aluminum carried out in 0.3M oxalic acid at the temperature of 20°C. This relatively high temperature shortens significantly the anodizing time and allows to fabricate quickly thick through-hole membranes without the additional operating cost of a cooling circuit. The structural features of anodic porous alumina such as pore diameter, interpore distance, porosity, pore density and pore circularity were investigated at various durations of pore opening/widening process carried out in 5% H3PO4. An excellent agreement of AAO structural features measured in FE-SEM images of the studied samples with results from software calculations was observed. The pore shape can be monitored qualitatively by fast Fourier transforms (FFTs) and quantitatively by calculation the percentage of pore circularity. Additionally, the regularity of the hexagonal arrangement of nanopores in through-hole AAO membranes was compared for various opening/widening time ranging from 40 to 100min. It was shown that three-dimensional (3D) representations of FE-SEM images and their surface-height distribution diagrams provide interesting information about the surface roughness evolution during the pore opening/widening process. A template-assisted fabrication of Ag and Sn nanowire arrays by electrochemical deposition into the pores of the prepared AAO templates was also successfully demonstrated. [Copyright &y& Elsevier]

Abstract: Rhodium phthalocyanin was shown to exhibit high catalytic activity toward oxalic acid oxidation in terms of the onset potential and current density. The onset potential for the oxidation of oxalic acid is much lower than those of the previous electrodes. The substrate specificity and the effect of anion were also examined. The results suggest that oxalic acid would first coordinate to the Rh center in the catalytic cycle. An amperometric sensor for oxalic acid was constructed using Rh phthalocyanin. This sensor worked at a low applied potential (0.75V vs. a reversible hydrogen electrode). The limit of detection of the sensor reached 1μM. [Copyright &y& Elsevier]

Abstract: Poly(N-ethylaniline) (PNEA) coatings were grown by cyclic voltammetry technique on copper from 0.1M N-ethylaniline (NEA) in 0.3M oxalic acid solution. The optimum conditions (e.g. upper potential limit, scan rate and cycle number) effect on corrosion performance of synthesized PNEA films were determined in order to obtain best protection results against corrosion. The electrodeposited coatings were characterized by cyclic voltammetry (CV), Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy and scanning electron microscopy (SEM). Redox parameters were found after electrochemical tests and results of stability tests of these films impart an electroactive behavior that is composed of both diffusion control and thin film behavior. In addition, corrosion performance of PNEA coatings were investigated in 0.1M H2SO4 by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) techniques. [Copyright &y& Elsevier]

Abstract: Aluminum covered with pore-sealed anodic oxide films was irradiated with a pulsed Nd–YAG laser to remove the oxide film at micro-areas. The specimen was re-anodized for long periods to examine the growth of porous anodic oxide films at the area where substrate had been exposed by measuring current variations and morphological changes in the oxide during the re-anodizing. The chemical dissolution resistance of the pore-sealed anodic oxide films in an oxalic acid solution was also examined by measuring time-variations in rest potentials during immersion. The resistance to chemical dissolution of the oxide film became higher with increasing pore-sealing time and showed higher values at lower solution temperatures. During potentiostatic re-anodizing at five 35-μm wide and 4-mm long lines for 72h after the film was removed the measured current was found to increase linearly with time. Semicircular columnar-shaped porous type anodic oxide was found to form during the re-anodizing at the laser-irradiated area, and was found to grow radially, thus resulting in an increase in the diameter. After long re-anodizing, the central and top parts of the oxide protruded along the longitudinal direction of the laser-irradiated area. The volume expansion during re-anodizing resulted in the formation of cracks, parallel to the lines, in the oxide film formed during the first anodizing. [Copyright &y& Elsevier]

Abstract: Aiming at a better understanding of ethylene glycol oxidation, the adsorption and oxidation of ethylene glycol and its incomplete C2 oxidation products glycol aldehyde, glyoxal, glycolic acid, glyoxylic acid and oxalic acid on carbon supported Pt catalysts were investigated by on-line differential electrochemical mass spectrometry (DEMS) under continuous electrolyte flow. This includes adsorption transients at different, constant potentials, oxidative removal (‘stripping’) of the resulting adsorbates, and potentiodynamic bulk oxidation/reduction of the respective molecules. The data show a pronounced influence of the different functional groups on the adsorption and oxidation characteristics, with hydroxyl and carboxylic functions resulting in lower adsorption rates and pronounced potential effects, while aldehyde functions lead to high adsorption rates at all potentials. The potential effects in the adsorption rate are mainly ascribed to surface blocking by Hupd species. For aldehydes and acids, CO2 formation occurs already at potentials below the onset of OHad formation, which is ascribed to the decomposition of the carboxylic group or of the diol groups of hydrated aldehydes. The contributions of different reaction pathways, including: (i) ‘direct’ oxidation to CO2, (ii) indirect oxidation to CO2 via formation and further oxidation of COad, and (iii) incomplete oxidation to more highly oxidized C2 species, with the possibility of their further reaction via re-adsorption and reaction along (i)–(iii), are discussed. [Copyright &y& Elsevier]

Abstract: Anodic aluminum oxide (AAO) membranes with a highly ordered nanopore arrangement typically serve as ideal templates for the formation of various nanostructured materials. A typical procedure of the template preparation is based on a two-step self-organized anodization of aluminum carried out at the temperature of about 1–3°C. In the current study, AAO templates were fabricated in 0.3M oxalic acid under the anodizing potential range of 30–65V at a relatively high electrolyte temperature ranging from 20 to 30°C. Due to a high rate of porous oxide growth, about 5–10-fold higher than in low-temperature anodizing, the process of the template fabrication can be shorten significantly. Similarly to the low-temperature anodization, the best hexagonal pore arrangement is observed for samples anodized at 40V. With a prolonged duration of the first anodizing step the order degree of triangular nanoporous lattice, observed after the second anodization, improves considerably. The effects of the anodizing potential and the process duration on the structural features of porous anodic alumina such as: pore diameter (D p), interpore distance (D c), porosity (P), pore density (n) and anodizing ratio (B U) were investigated in details at various temperatures. The obtained results were compared with theoretical predictions and data reported in the literature. [Copyright &y& Elsevier]

Abstract: The electrochemical behavior of pure Ti and Ti-6Al-4V alloy was investigated in oxalic acid solution using various electrochemical techniques, i.e. open circuit potential (OCP), potentiodynamic polarization, electrochemical impedance measurements (EIS) and surface examination via scanning electron microscope (SEM) technique. The influence of concentration and temperature on the electrochemical behavior of TI and its alloy were also studied. The results of polarization measurements showed that corrosion current density (i corr) increases with increasing either temperature or oxalic acid concentration for both samples. Moreover, the value of i corr for Ti was found to be lower than that for Ti–6Al–4V alloy, where the corrosion resistance for titanium was always higher. The effect of additives as SO4 2− and Cl− ions was studied; results indicated that the oxide film resistance (R ox) value decreases with increasing the concentration of SO4 2− ion. However, for Cl− ion, the value of R ox decreases with increasing Cl− ion concentration up to 1mM before it starts to increase at higher concentrations. EIS and polarization results are in good agreement with each other. The obtained results were confirmed by surface examination. [Copyright &y& Elsevier]

Abstract: The growth of nanoporous alumina on concave or convex aluminium surfaces has been investigated. The number of pores during anodic oxidation increases or decreases almost linearly with the thickness of the oxide which is due to bifurcation or termination of single pores during alumina growth. The anodic oxidation has been constantly conducted in oxalic acid at 40V. Therefore the average interpore distance has not changed during alumina growth. In earlier papers it has been shown that a bifurcation of pores is the result of the change of voltage and the electrolyte. In this work we have demonstrated that a termination or a bifurcation of pores is also possible by structuring the aluminium to a curved surface with concave or convex properties before oxidation. Those results do not depend on the substrate characteristics or on the alumina preparation techniques. [Copyright &y& Elsevier]

Abstract: In recent years, the possibility of using anodized aluminium as a template to obtain nanowires and nanotubes via electrodeposition has been firmly established. The main problem with this method is the high electrical resistance generated by the barrier layer that isolates the metallic base from the electrodeposition bath. An easy way to decrease this resistance is to perform an additional step before deposition: a barrier layer thinning (BLT) process . Different BLT procedures have been described and although some of them work well, the process is not yet well understood. Here, we present an optimized stepped galvanostatic BLT process and discuss how BLT is achieved. As opposed to the common belief that BLT takes place via dendritic porous growth at the bottom of the porous anodic alumina (PAA), we show that during thinning, a controllable branched-shaped porous structure is generated. Finally, we also analyze the use of stepped techniques to obtain alumina templates with narrower pores than expected in an oxalic acid bath. [Copyright &y& Elsevier]

Abstract: A cobalt phthalocyanine bulk-modified carbon ceramic composite has been prepared by using sol–gel processing, and characterized by BET surface area, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. A water-soluble 3-n-propylpyridinium chloride silsesquioxane (SiPyCl), an ion exchanger polymer, was employed to attach cobalt(II) tetrasulfophthalocyanine (CoTsPc) and prevent its leakage, as well as, to ensure adequate dispersion in the sol–gel network. The modified electrode built in a rigid disk-format displayed good electrocatalytic behavior towards the oxidation of oxalic acid at 0.84V (SCE), as evidenced by the enhancement of the anodic current peak intensity when the concentration of oxalic acid was increased. A linear response was found in the range of 1.6×10−5 to 1.5×10−3 moll−1 with a detection limit of 7.1×10−6 moll−1. [Copyright &y& Elsevier]

Abstract: The electrochemical incineration of oxalic acid (OA) at Ti/IrO2–Ta2O5 (DSA-O2) anode was investigated to find the influence of the operative parameters on the performances of the process. Polarization curves and chronoamperometric measurements indicate the probable occurrence of a direct electrochemical oxidation of OA at the surface of the DSA anode. In incineration electrolyses, the performances of the process in terms of OA conversion and current efficiency dramatically depend on the adopted operative conditions. Interestingly, very high OA removal and current efficiency were obtained when the process was performed at relatively high temperatures (50°C) or in the presence of NaCl. The experimental results are in good agreement with the previsions of a simple theoretical model previously developed. [Copyright &y& Elsevier]

Abstract: An Al/Ta bilayer specimen prepared by a successive sputter-deposition of a 150-nm tantalum layer and a 180-nm aluminium layer onto a silicon wafer is anodically processed in a sequence of steps in oxalic acid electrolytes, at voltages of up to 53V, which generates a 260-nm alumina film with well-ordered nanoporous structure. Further potentiodynamic reanodizing the specimen to 220V causes the simultaneous growth of a 65-nm tantalum oxide layer beneath the alumina film and an array of oxide ‘nanocolumns’ (∼50mn wide, ∼80nm apart, ∼7×109 cm−2 population density) penetrating the alumina pores and reaching precisely to the top of the alumina film. The complete filling of the alumina pores is assisted by the high Pilling–Bedworth ratio for Ta/Ta2O5 and a substantially increased transport number for tantalum species (0.4), which is an average value of all migrating tantalum ions with different oxidation states. The nanocolumns are shown to be composed of a unique, regular mixture of Ta2O5 (dominating amount), suboxides TaO2 and TaO x (0.5< x <1), Al2O3, metallic Ta and Al aggregates, tantalum diboride (TaB2) and oxidized boron from the electrolyte. The ionic transport processes determining the self-organized growth of these planar oxide nanostructures are considered and described conceptually. [Copyright &y& Elsevier]

Abstract: The tris-2,2′-(bipyridine) ruthenium(II) complex derivative, which shows the electrogenerated chemiluminescence (ECL) reaction, was directly immobilized on the boron-doped diamond (BDD) surface with three types of modification to form C–N, C–O and C–C bond between them. The objective of this study is to find the most appropriate modification method for the highest amount of immobilization on diamond and the highest stability for electrochemical reaction in the high potential ranges. By making use of this photofunctional BDD, the establishment of an analytical system for the selective and high-sensitive detection of oxalic acid in human urine using the ECL reaction was attempted. Comparing the stability for the ECL reaction among three modified BDD (MBDD) electrodes using the long-term potential cycling, in the initial of cycling, the ECL peak intensity for modified BDD linked with C–C bond (MBDD(C–C)), with C–N bond (MBDD(C–N)) and with C–O bond after the exposure to O2 plasma (MBDD(C–Opl)) were in the same range. At MBDD(C–C), the ECL intensity was very stable and initial value was maintained even after 200min of the potential cycling, but the ECL intensities for other modified BDD were rapidly decreased, indicating that the modification method through C–C bond can provide the high density and stable modification. Using MBDD(C–C), the analysis for oxalic acid in human urine was carried out by the high-performance liquid chromatography (HPLC) and flow injection analysis (FIA) systems in that the electrochemical amperometric detector (ECD) and ECL detector with modified BDD were installed. In the HPLC-ECD chromatogram, many peaks including uric acid and ascorbic acid were observed. On the other hand, only one peak was detected in the HPLC-ECL chromatogram, indicating that oxalic acid could be selectively detected in human urine using the ECL reaction at modified BDD. The linear dynamic range and the lowest detection limit (S/N=3) for the oxalic acid detection at MBDD(C–C) were achieved to be 2 orders of magnitude from 5μM to 100μM and 5μM, respectively. MBDD(C–C) was proven to have sufficient sensitivity for oxalic acid in human urine (average concentration 500μM). [Copyright &y& Elsevier]