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• Anion intercalation in graphite produces pressurized blisters on the basal plane. • Mechanical characterization of these pressurized blisters can be used as model system. • Blisters show a stiffness in a range between 1 and 10 MPa. • Blisters can be moved or cut by an AFM tip. • The deformation of graphite basal plane by blisters seems to be elastic. Electrochemical anion intercalation of highly oriented pyrolytic graphite in mineral acids (such as sulfuric, perchloric, etc.) represents a model system to study (i) the intercalation process of chemical compounds in stratified crystals; (ii) the evolution of gases at the surface and inside the sample and (iii) the evolution of swollen regions of graphite, called blisters. Although the explanation of the blister evolution mechanism can be dated back to the nineties of the last century, many chemical and physical properties have been explored only very recently. In particular, the mechanical properties of blisters on graphite are not widely discussed in the literature. Here, we employ in-situ atomic force microscopy (AFM) to characterize the blister stiffness. The same AFM tip is used to move mechanically the blister on the basal plane or even cut it. As a consequence of this operation, the entrapped gases (namely, CO, CO 2 and O 2) can deflate and the swollen graphite layers lay down to recompose the graphite basal plane. [Display omitted] [ABSTRACT FROM AUTHOR]

• Carbonized polyacrylonitrile (cPAN)-coated 3D porous TiP 2 O 7 was simply fabricated. • N-doped carbon coating layer improved the electronic conductivity of TiP 2 O 7. • Oxygen vacancies induced by N-doping facilitated Li+ diffusion and pseudocapacitance. • The designed TiP 2 O 7 /cPAN anode revealed outstanding rate capability. TiP 2 O 7 is a hopeful anode material for lithium-ion batteries (LIBs) due to its three-dimensional (3D) open skeletons, excellent ion transfer kinetics, and good structural stability. However, the inferior intrinsic electronic conductivity degrades seriously the electrochemical performance of LIBs. Herein, a strategy of carbonized polyacrylonitrile-coated TiP 2 O 7 (TPO/cPAN) with 3D porous structures was proposed to enhance Li+-storage capability. The TPO/cPAN modified with 30 wt% polyacrylonitrile and calcined at 800 ℃ delivers superior long-term cycling stability at 0.5 A g−1 and excellent rate capacities of 558.7, 523.8, 477.5, 409.8, and 303.4 mAh g−1 at 0.1, 0.2, 0.4, 0.8, and 1.6 A g−1, respectively. Structural characterizations and electrochemical analysis reveal that the pyrolytic N-doped carbon layer markedly ameliorates the electron transferability and protects the electrode from organic electrolyte erosion. Meanwhile, the design of 3D porous structures and the generation of rich oxygen defects facilitate Li+ transport and pseudocapacitance energy storage. The work provides a novel pathway for optimizing the electron/ion migration of polyanionic electrode materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• Scanning electrochemical cell microscopy can be applied to biological thin film voltammetry. • Voltammetric movies give new insights into complexity of bio-functionalised electrodes. • Quantitative analysis reveals electrode-dependant variability of coenzyme Q 10 behaviour. The field of bioelectrochemistry continues to develop due to diverse applications ranging from biosensors to biotechnology and biofuel cells. Accordingly, research understanding the fundamental energy conversion step(s) in these systems (namely electron transfer) will enable the construction of more efficient and better characterised (bio)electrodes. This work investigates surface-confined coenzyme Q 10 on glassy carbon (GC-coQ 10) and highly ordered pyrolytic graphite (HOPG-coQ 10) electrodes using scanning electrochemical cell microscopy (SECCM) in the cyclic voltammetric hopping mode regime. Although frequently studied in bulk at macroscopic electrodes, this is the first report where SECCM has been used to explore how the electrode surfaces employed influences the electrochemical response of immobilised biomolecules in a spatially resolved manner. Full SECCM scans comprised of 1600 cyclic voltammetric measurements on GC-coQ 10 and HOPG-coQ 10 electrodes demonstrate and quantify the microscopic variability in responses of coQ 10 on these surfaces. The HOPG-coQ 10 electrode shows a significantly larger distribution of key parameters compared to the GC-coQ 10 electrode, such as the voltammetric peak-to-peak separation (∆ E p = 0.87 ± 0.02 V and 0.426 ± 0.008 V on HOPG and GC, respectively) and peak full width at half maximum (e.g., anodic FWHM = 0.25 ± 0.02 V and 0.202 ± 0.003 V on HOPG and GC, respectively). Of note, a unimodal mid-point potential (E mid) distribution is observed for GC-coQ 10 (E mid = -0.150 ± 0.002 V vs. Ag|AgCl) whilst a bimodal distribution is seen on HOPG-coQ 10 (E mid = -0.11 ± 0.01 and -0.06 ± 0.01 V vs. Ag|AgCl). This study provides a proof of concept that SECCM can be applied to electrode systems commonly used in classical bioelectrochemistry, highlighting the potential of this technique to be used in diverse application areas. [Display omitted] [ABSTRACT FROM AUTHOR]

The objective of this work is to explore whether carbon materials, which are usually utilized as additives for improving the electronic conductivity of oxide-based oxygen evolution reaction (OER) catalysts, could be replaced by silver nanoparticles. We integrate La 0.75 Sr 0.25 Mn 0.5 Co 0.5 O 3−δ , a perovskite with a limited electronic conductivity, in electrode compositions with either carbon materials (pyrolytic carbon of the Sibunit family – Sibunit-152, furnace black – Vulcan XC-72R, and Acetylene black) or silver nanoparticles, and investigate their OER activity in 1 M NaOH solution. We apply the rotating ring-disk electrode (RRDE) technique to separate the OER currents from those originating from corrosion of the additives under anodic polarization. We conclude that certain carbon materials would be better suited for use as conductive additives for oxide-based OER catalysts than silver particles. [ABSTRACT FROM AUTHOR]

Guanine, having lower one-electron oxidation potential than other nucleobases, is of relevance to oxidative degradation of nucleic acids in mutagenesis, carcinogenesis, and aging. Here we compare oxidation potentials of guanine (G), guanosine (Guo), deoxyguanosine (dGuo), guanosine -5′- monophosphate (GMP) and 2′- deoxyguanosine -5′- monophosphate (dGMP) obtained by theoretical and experimental methods. Structures of G species were optimized and the identities of minima were verified by vibration frequency calculations. Redox equilibria were modelled in terms of corresponding thermochemical cycles. The changes in free energy were calculated at DFT level using the two different functionals: (i) general purpose B3LYP functional, and (ii) more specific ωB97X-D functional (both with 6-31 + G(d) basis set). Experimental oxidation potentials of all G analogues were measured voltammetrically on a polymer pencil graphite electrode (pPeGE) providing the best results from all carbon electrodes used (glassy carbon electrode, basal and edge plane pyrolytic graphite electrodes). The oxidation process is strongly dependent on the pH value and with increasing pH a linear shift of G oxidation peaks (E pa) towards negative potentials is observed. The theoretically and experimentally obtained oxidation potentials were compared for the pH 5. Anodic peak potentials increase in the order G « dGMP ≤ GMP < dGuo ≤ Guo and correlate with the calculated thermodynamic redox potentials as well as with NBO charges in purine moiety. The oxidation of deoxy analogues was predicted theoretically to occur at lower potentials than that of corresponding parent compounds and this fact was experimentally verified. The assumption that due to negatively charged phosphate group of GMP or dGMP their oxidation potentials could be observed at lower positive potential has not been confirmed and the significant difference (more than 200 mV) between the oxidation potentials of G nucleobase and its nucleosides and nucleotides is discussed. Moreover, conformity of theoretical and experimental data for radicals (cation, neutral) indicates that while the deprotonation process of G differs from its analogues, the oxidation process of all species takes place on imidazole ring. Image 1 • Theoretical (DFT) and experimental (LSV on pPeGE) oxidation potentials of guanine (G) and its derivatives (d)Guo, (d)GMP. • Free energy changes in oxidation reactions of G species calculated using two different functionals (B3LYP and ωB97X-D). • Deoxy-G species require less energy in oxidation than their oxo parent compounds (agreement of theory and experiment). • The detailed NBO charge analysis of all G substances indicates the oxidation processes occurring on imidazole ring. • Differences in deprotonation: while the proton at N9 is decisive for G, the proton at N1 is crucial for other G derivatives. [ABSTRACT FROM AUTHOR]

• A complex voltammetric study of Sudan I and products of its redox transformations. • The first comparative study of voltammetric behavior of major Sudan I metabolites. • Distinction of Sudan I and its major metabolites by voltammetry is possible. • Adsorption of analytes on basal plane PGE enhances sensitivity compared to BDDE. • Sudan I and its metabolites can be detected in excess of NADPH. Sudan I (1-(Phenyldiazenyl)naphthalen-2-ol) is an orange industrial azo dye. It is utilized as a marker substrate in studies of metabolic transformation of xenobiotics through processes involving cytochrome P450 hydroxylase. In this complex study, redox and subsequent chemical/electrochemical reactions of Sudan I and its three major metabolites (4′‑hydroxy, 6‑hydroxy, and 4′,6-dihydroxy derivatives of Sudan I) were investigated using boron doped diamond and basal plane pyrolytic graphite electrodes. Cyclic voltammetry (CV) in Britton – Robinson buffer pH 7 showed distinct differences in the number and potential of signals, depending on the number and positions of the hydroxy groups. While in CV scans initiated in anodic direction, primary oxidations of paired or unpaired hydroxy groups are dominating, cathodic scans lead primarily to reduction of the azo group and to cleavage of the parent compounds and formation of 1-aminonaphthalen-2-ol and aniline or their corresponding hydroxylated derivatives. These are oxidizable in reverse anodic scans. Combinations of CV scans can be used to distinguish among all tested compounds. Basal plane pyrolytic graphite electrode provides better sensitivity than boron doped diamond electrode due to enhanced adsorption of the aromatic analytes/intermediates. The possibility of detecting Sudan I and its metabolites in the presence of excess amounts of NADPH as an essential component of enzymatic hydroxylation systems, was tested. Although the oxidation signal of NADPH partially interferes with signals of primary oxidation of hydroxy groups (particularly for Sudan I), our results suggest that electrochemical assays could be applicable in monitoring transformation of Sudan I in biochemical studies. [Display omitted] [ABSTRACT FROM AUTHOR]

We present the utilization of the novel hybrid electrochemical DNA biosensor, as well as the fabrication and testing of novel dGMP (2′-deoxyguanosine 5′-monophosphate) (bio)sensor based on anodically pre-treated "basal-plane" pyrolytic graphite electrode (BPPGE) for the investigation of the interaction between double-stranded DNA (dsDNA) and neonicotinoid insecticide clothianidin (CLOT) via linear-sweep voltammetry (LSV). The results clarify the nature of the interaction as partial-intercalation (marked by high preference towards guanine bases) with binding constant (K b) of 8.1 × 105 L/mol, free Gibbs energy (∆ G 0) of −33.154 kJ/mol, and site-binding size (s) of 0.58 bp. The conclusions obtained by LSV are further supported by molecular docking that confirmed a partial-intercalative mode of interaction with the predominant involvement of the hydrogen bonds (exclusively with the guanine bases) for the stabilization of dsDNA-CLOT complex. [ABSTRACT FROM AUTHOR]

Li-rich Mn-based cathode materials (LRM) have attracted extensive attention as key cathode material for achieving high energy density in lithium ion batteries. However, the irreversible oxygen precipitation and structural transformation during its cycling process, resulting in capacity and voltage degradation have heavily hindered practical applications. The Co-free Li-rich Mn-based cathode material Li 1.2 Ni 0.185 Mn 0.585 Fe 0.03 O 2 by the modified Pechini method, the AlPO 4 -Li 3 PO 4 double shell was formed in situ on its surface. The AlPO 4 protective layer formed by the highly electronegative (PO 4)3- with not only effectively inhibits the precipitation of surface oxygen, but also suppresses the interfacial side reactions and transition metal dissolution, thus raising the cycling performances. The formation of the outer Li 3 PO 4 helps to remove the residual Li+ on the surface, accelerates the diffusion and charge transfer process of Li+ at the electrode/electrolyte interface. The synergistic modification of the AlPO 4 -Li 3 PO 4 dual shell can significantly improve the cycling stability and rate performance. In particular, the 3% modified sample with a capacity retention of 74.8% after 200 cycles at 0.2 C. The first discharge specific capacity is 260.73 mAh g-1 at 0.1 C, and the initial coulombic efficiency reaches 84.96%. The lithium-ion full cell employing 3% and graphite exhibit a specific energy density of 440 Wh kg-1 at 0.1 C, and shows the best cycling stability with 78.3% capacity retention over 100 cycles at 1 C. The AlPO 4 -Li 3 PO 4 double shell was formed in situ on LRM surface, the AlPO 4 protective layer formed by the highly electronegative (PO 4)3− with not only effectively inhibits the precipitation of surface oxygen, but also suppresses the interfacial side reactions and transition metal dissolution, thus raising the cycling performances. The formation of the outer Li 3 PO 4 modified layer helps to remove the residual Li+ on the surface, accelerates the diffusion and charge transfer process of Li+ at the electrode/electrolyte interface. The synergistic modification of the two can significantly improve the cycling stability and rate performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Carbon's electrochemistry depends on its type and microstructure, and how these affect the electrode's electronic density of states. We demonstrate how pyrolysis of electro-mechanically stressed Polyacrylonitrile (PAN) nanofibers, infused with carbon nanotubes, will result in a unique graphitic electrode, which possesses enhanced and multifaceted electrochemical behavior. As corroborated by materials characterization, the microstructure of the stress-activated pyrolytic carbon (SAPC) characteristically contains a high proportion of disorders in the forms of edge planes and embedded heterogeneous nitrogen atoms. These disorders introduce a range of energy states near the Fermi level, yielding enhanced kinetics in the as-synthesized SAPC electrodes. A comprehensive electrochemical study of the SAPC electrode in surface sensitive ([Fe(CN) 6 ]3-/4-), surface insensitive ([IrCl 6 ]2-/3-), and adsorption sensitive (dopamine) redox probes demonstrates 5–14-fold increases in its heterogeneous electron transfer rate compared to regular PAN-based carbon electrodes. The fast kinetics of SAPC electrodes in adsorption sensitive analytes translates into its capability for simultaneous detection of dopamine, uric acid, and ascorbic acid. The results point to a new class of pyrolytic carbon electrodes with an attractive electrocatalytic capacity, geared toward electrochemical sensing platforms. Highlights • Pyrolysis of stress-treated polymer nanofibers results in graphitized carbon. • Microstructure of pyrolyzed carbon is rich in edge planes and nitrogen heteroatoms. • Disorder-induced electroactive sites enhance carbon probes electrochemical kinetics. • Stress-activated carbon can simultaneously detect dopamine, uric and ascorbic acids. • Electrocatalytic activity of stress-activated carbon holds promise for sensing. [ABSTRACT FROM AUTHOR]

A simple electrochemical assay to monitor the dispersion of Pseudomonas aeruginosa PA01 biofilm is described. Pyrolytic graphite (PG) electrodes were modified with P. aeruginosa PA01 using layer-by-layer (LbL) methods. The presence of the bacteria on the electrodes was directly monitored using square wave voltammetry (SWV) via the electrochemical reduction of electroactive phenazine compounds expressed by the bacteria, which indicate the presence of biofilm. Upon treatment of bacteria-modified electrodes with a 2-aminoimidazole (2-AI) derivative with known Pseudomonas anti-biofilm properties, the bacteria-related electrochemical reduction peaks decreased in a concentration dependent manner, indicating dispersal of the biofilm on the electrode surface. A similar 2-AI compound with negligible anti-biofilm activity was used as a comparative control and produced muted electrochemical results. Electrochemical responses mirrored previously established bioassay-derived half maximal inhibition concentration (IC 50 ) and half maximal effective concentration (EC 50 ) values. Biofilm dispersal detection via the electrochemical response was validated by monitoring crystal violet absorbance after its release from electrode confined P. aeruginosa biofilm. Mass spectrometry data showing multiple redox-active phenazine compounds are presented to provide insight into the surface reaction complexity. Overall, we present a very simple assay to monitor the anti-biofilm activity of compounds of interest. [ABSTRACT FROM AUTHOR]

Electropolymerisation of riboflavin (Rf) was performed in different media in order to optimise the best conditions for the creation of a stable and electroactive polymerised riboflavin (PRf) film. Electropolymerisation was performed using cyclic voltammetry (CV) in solutions with various pH in different potential windows. Different electrode substrates were used for PRf deposition: pyrolytic graphite (PG) and highly oriented pyrolytic graphite (HOPG). The obtained films were characterised spectroscopically, microscopically and electrochemically applying Raman spectroscopy, reflection-absorption infrared spectroscopy (RAIRS), atomic force microscopy (AFM) and electrochemical methods such as cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) in different media. The best film was obtained when PRf was electropolymerised from 0.1 mol L −1 PBS, pH 7.0. Raman and RAIRS data have indicated involvement of isoalloxazine ring III in the polymerisation process. The best response of such an electrode was in the same buffer solution. This electrode will be further applied in (bio)sensor construction. [ABSTRACT FROM AUTHOR]

• Concentrated Gua forms multilayered architecture on basal-oriented pyrolytic graphite. • Multilayer formation due to Gua-Gua stacking produces G S ox peak around 1.1 V. • Less concentrated Gua forms planar-arranged network accompanied by peak Gox at 0.8 V. • The multilayered supramolecular architecture was not detected for concentrated Ade. In this work we experimentally show the formation of a planarly-arranged guanine multilayer on a pyrolytic graphite surface, which was predicted by theoretical calculations at the ideal graphene surface. In the case of adenine, a multilayered architecture like that of guanine was not confirmed. Changes in the purine bases' arrangement on charged surface in dependence on their concentration is studied using electrooxidation peaks of guanine and adenine, together with time changes in capacitance of electric double layer. Existence of predicted guanine multilayers is supported by electrochemical findings and confirmed by atomic force microscopy. Moreover, our data suggest a link between an additional guanine electrooxidation peak and supramolecular guanine assembly formation. [Display omitted] [ABSTRACT FROM AUTHOR]

Demand for more efficient energy storage devices stimulates efforts to search and develop new materials and composites with promising properties. In this regard, composite materials, including carbonaceous materials and metal oxides have attracted a great attention due to better electrochemical performance as compared to their single material analogues. For the first time, herein, we report a new and simple procedure for preparing porous highly oriented pyrolytic graphite/nickel hydroxide composite (P–HOPG/Ni(OH) 2 ) via a fast and simple two-step electrochemical method including potentiostatic routes. In the first step, a low anodic potential (2 V) was applied to pristine HOPG in 0.5 M H 2 SO 4 solution for 240 s to produce porous P–HOPG, followed by a cathodic potential (−1.5 V) in acetate buffer solution to reduce surface functional groups and increase conductivity of the electrode. In the next step, the resulting porous material composed of graphene-like sheets was used as a new binder-free substrate for electrodeposition of flower-like nickel hydroxide structures at a constant potential of −1.3 V for 300 s. This new procedure does not need any thermal treatment of the substrate at high temperatures. The resulting modified electrode afforded extremely high areal capacitance of 5.2 F cm −2 at a current density of 2 mA cm −2 . FE-SEM results showed that nickel hydroxide nanoflower-like structures deposited on the graphene-like sheets in P–HOPG substrate. This new morphology facilitates electron transfer through the modified electrode. A good cycling stability was observed for the modified electrodes in alkaline media. EIS measurements showed low values of internal resistance ( R s ) and charge transfer resistance ( R ct ) for the modified electrodes, indicating that the prepared nanocomposite is appropriate for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Sensitive and simple electroanalytical methods were developed for the determination of the loop diuretic furosemide (FUR) in pharmaceutical formulations and synthetic urine samples by coupling square-wave voltammetry (SWV) with polished basal-plane pyrolytic graphite (BPPG) or cathodically pretreated boron-doped diamond (BDD) and amorphous carbon nitride (a-CN x ) as working electrodes. The analytical parameters obtained with the three methods were compared. With BPPG, best results were attained using 0.10 mol L −1 H 2 SO 4 as supporting electrolyte, whereas with BDD and a-CN x , this was attained using a 0.040 mol L −1 BR buffer (pH 4.5). Cyclic voltammograms obtained for FUR evidenced an irreversible behavior (with two oxidation peaks), in agreement with the literature. On the BDD and a-CN x electrodes, the electrooxidation of FUR is a purely diffusion-controlled process, whereas on the BPPG electrode some degree of adsorption is also involved. The obtained linear response ranges (detection limits) for the BPPG, BDD, and a-CN x electrodes were 0.60–4.8 (0.47), 0.30–13 (0.30), and 0.50–99 (0.39) μmol L −1 , respectively. The proposed methods were successfully applied in the determination of FUR in pharmaceutical formulations (tablets), with results similar to those obtained using a reference spectrophotometric method (at a confidence level of 95 %), and in the recovery of FUR in synthetic urine samples. The analytical conditions obtained with the novel SWV methods here reported are comparatively better than those for other electrochemical methods in the literature. As the pretreatment procedures are much simpler for BDD and a-CN x than for BPPG, one can conclude that the former two materials can be advantageously used to determine FUR with good sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

A simple electrochemical assay to monitor the alginate penetration ability of a series of antimicrobial peptides (AMP) containing unnatural amino acids is reported. Alginate, a component of P. aeruginosa biofilms, was used to modify pyrolytic graphite (PG) electrodes using well-established layer-by-layer (LbL) protocols, followed by exposure to AMP at varying concentrations for increasing lengths of time. Intact alginate layers inhibited surface binding and electron transfer of solution phase ferricyanide based on anionic repulsion. AMP exposure resulted in concentration-dependent alginate penetration, and an increase in electrochemical current at negative-shifted potentials. Controls showed that the AMP unnatural amino acid and cationic structure was important in facilitating alginate penetration. In an effort to validate this simple model as a potential anti-biofilm assay, biofilm dispersal and inhibition assays were performed in 96-well plates using Pseudomonas aeruginosa PAO1. The biological assays showed that the AMP were effective at dispersing PAO1 biofilm, providing a level of validation to the simple alginate electrochemical assay. [ABSTRACT FROM AUTHOR]

Pyrolytic lignin (PyL) and zinc borate (ZB) are added to poly (acrylonitrile-co-itaconic acid) (PANIA) to facilitate the fabrication and improve the electrochemical performance. The carbonised PANIA/PyL/ZB (CPPZ) anodes with in-situ self-doped nitrogen are fabricated, demonstrating a higher char yield, a higher fabrication efficiency, and optimal carbon structures. It finds that PANIA, PyL and ZB have synergic effects with each other on improving thermal stability, resulting in a 16.21% enhancement of residue at 700°C from the calculated value. During thermal stabilisation, PyL and ZB accelerate the formation of conjugated ladder structures at 230°C. After carbonisation under 700°C, CPPZ-700 has relatively higher contents of pyridinic N (34.62%) and pyrrolic N (50.43%), and a larger interlayer space (0.46 nm). As an anode of sodium-ion battery, CPPZ-700 illustrates a reversible specific capacity of 180 mAh g−1 at a current density of 100 mA g−1, which is 120 mAh g−1 higher than PANIA-based carbon anode under the same conditions. [ABSTRACT FROM AUTHOR]

This study reports on the crucial effects of the ratio of electrolyte volume to electrode area on redox reactions of graphite anodes for lithium-ion batteries (LIBs). It is found that a pyrolytic graphite edge plane electrode (PGE) exhibits reversible Li + transport behavior in LiClO 4 solution, but shows a suppressed redox reaction in LiPF 6 electrolyte. The reversible Li + transport in LiClO 4 is hampered by the presence of trace HF, while the depressed activity in LiPF 6 is improved by adding an HF scavenger, which points to the suppressive effects of HF on the redox behavior of PGE. In addition, the redox activity of PGE in LiPF 6 solution is either enhanced by decreasing electrolyte volume or diminished by decreasing surface area. It is also revealed that graphite composite electrodes of practical LIBs are also subject to the influence of HF if an excessive amount of electrolyte is employed. These observations are attributed to the HF-induced formation of a passive LiF layer, which is facilitated at high ratio of electrolyte volume to electrode area. Our results clearly demonstrate that HF impurity significantly suppresses the redox activity of graphite anodes, and that the adverse HF influence becomes predominant at a high electrolyte-to-electrode ratio. [ABSTRACT FROM AUTHOR]

In this paper, polypyrrole (PPy) and benz[a]anthracene-7,12-dione (BaD) were electro-polymerized onto a pyrolytic graphite electrode (PGE), constructing a novel BaD/PPy/PGE platform for electrochemical sensoring. The morphology and electrochemical properties of the fabricated BaD/PPy/PGE were characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Furthermore, the electrochemical behavior of benzo[k]fluoranthene (BkF) at the BaD/PPy/PGE was investigated. Due to the specific interactions between BkF and BaD, a wide linear range of BkF detection from 1.0×10−12 to 1.0×10−9 M with good linearity (R2 =0.9962) and a low detection limit (1.0×10−13 M, S/N=3) were demonstrated. Importantly, other similar aromatics which had one ring or more than two rings, such as benzo[a]anthracene, benzo[a]pyrene, pyrene, benzo[ghi]peryle, anthracene, phenanthrene, naphthalene and parachlorophenol, showed insignificant interference on BkF detection. Consequently, this novel BaD/PPy/PGE with excellent stability and selectivity holds promise as an effective BkF electrochemical sensor in aqueous solution. As an example for its practical application, the newly developed sensor was applied to quantitative determination of BkF in waste water samples obtained from a coking plant with satisfactory sensitivity, selectivity, and reversibility. [ABSTRACT FROM AUTHOR]

Highlights: [•] WE examined the electrochemical behaviors of Co octaethylporphyrin (Co-OEP) on HOPG. [•] Co-OEP exhibits reversible voltammograms at high potentials on HOPG in sulfuric acid. [•] Some anions (halides and ClO4 −) affect the redox behaviors. [•] The high potential can be explained by the effect of ClO4 −. [•] Halides decreased CO oxidation by the Co porphyrin, while ClO4 − did not. [ABSTRACT FROM AUTHOR]

Abstract: One- and two-dimensional cuprous oxide (Cu2O) nanostructures were fabricated on highly orientated pyrolytic graphite (HOPG) by electrodeposition in CuSO4 at room temperature (25°C) with no additives. For short deposition times, 1D Cu2O single nanocrystals were generally of an octahedral shape with sizes ranging from 50nm to 400nm, while 2D Cu2O nanowires with diameters ranging from 100nm to 300nm had lengths of more than 100μm. With longer deposition times, microwires were found to have diameters ranging from 1μm to 2μm with lengths up to 60μm, while microcrystals were also produced with sizes 1μm to 6μm. The highly aligned Cu2O nano/microwires were found to be deposited on the step edges of the HOPG substrate. Various crystal morphologies including flower-like and butterfly-like structures, and dendrites and truncated octahedra were observed on the working electrode of HOPG. Some of the morphologies are revealed for the first time by one step electrodeposition and these are confirmed to be single Cu2O crystals. [Copyright &y& Elsevier]

Highlights: [•] First order faradaic phase transition of dibenzyl viologen (dBV) at HOPG was studied. [•] At high Br− concentration, dBV exhibits two-step phase transitions. [•] As the first reduction step, a dBV + Br− mesophase emerges at [Br−]>75mM. [•] As the second, phase transition from the mesophase to a 2D condensed phase occurs. [•] Remarkable effect of Br− upon the transition enabled us to model the mesophase. [Copyright &y& Elsevier]

Abstract: We investigated the morphology of electrodeposited copper (Cu) onto self-assembled gold nanoparticles (Au NPs) modified highly oriented pyrolytic graphite electrode. A well organized and dense superstructure of Cu dendrites was prepared. By controlling the temperature, polyhedral particles were obtained. The mechanisms behind the formation of the superstructure and morphologies are analyzed and discussed based on the results of FEGSEM, XRD and X-ray photoelectron spectroscopy (XPS). The influence of self-assembled Au NPs template and Cu surface modification with dodecanethiol was discussed. [Copyright &y& Elsevier]

• The plasma gas is the crucial factor to manipulate surface chemistry on pyrolytic carbon. • The plasma-induced surface chemistry correlates with the properties of pyrolytic carbon as electrode material. • The plasma treatment of carbon can be considered as a fast and low-cost way of controllable variation of electrochemical performance in respect to outer-sphere redox systems. Plasma technology is a widely used approach for carbon activation and enhancing the surface energy by generating various functional groups. Gas selection is an important factor determining the type of functional groups to be formed on carbon surfaces. In this study, we investigate the impact of plasma-induced chemical surface alterations on performance of pyrolytic carbon as electrode material. Pyrolytic carbon electrodes were microfabricated by pyrolysis of SU-8 structures defined using UV lithography and treated using Ar, O 2 , N 2 and air plasma gases. The resulting surface chemistry and geometry were characterized by X-ray photoelectron spectroscopy and atomic force microscopy. Close inspection of electrochemical properties was done by using both outer (Ru(NH 3) 6 3+/2+) and inner (Fe(CN) 6 3-/4− and dopamine) redox systems. The electrochemical performances of the carbon electrodes treated with various plasma gases were compared based on information on heterogeneous electron transfer rates determined by cyclic voltammetry and electrochemical impedance spectroscopy. This work provides a fundamental insight into electrochemistry of plasma-modified pyrolytic carbon surfaces and strategies on how to enhance surface properties overcoming possible electron transfer limitations for future enhancement in carbon-based electrochemical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• Pyrolytic residues of waste plastics were thermally treated with KOH and NH 3. • The resultant carbon is used as a sulfur host in lithium sulfur batteries. • TiO 2-x and nitrogen in the carbon contributed to anchoring lithium polysulfides. • The Li-S cell delivers a low capacity fading of 0.089% with 500 cycles at 1 C. Lithium-sulfur (Li-S) batteries have the potential to provide high energy density but they suffer from shuttling phenomena that are detrimental to cyclic stability in such a way that lithium polysulfides gradually diffuse out from the cathode interface. We employed the pyrolysis residue from waste plastics for a carbon source and applied it as a cathode sulfur host for Li-S batteries to limit the shuttle effect. Annealing with the aid of KOH and the subsequent ammonia thermal treatment endowed the residue with hierarchical porosity that reached 30% mesoporosity of the total pore volume. N-defects were significantly introduced in carbon networks with edge-positioned states, which helped them chemically interact with Li moieties in the polysulfides. Furthermore, titanium sub-dioxide (TiO 2-x) was formed as impurities after the thermal treatment effectively suppressed diffusion of the intermediates. Based on the coupled effect of both N-defects and TiO 2-x , the prepared carbon contributed to retarding the decay rate of discharge capacity, and its decay rate decreased to 0.089% per cycle at 1 C until 500 cycles with a capacity of higher than 500 mAh g−1. This study offers a precedent for practical green design of waste plastic residues as a carbon source. [Display omitted] [ABSTRACT FROM AUTHOR]

The layered transition metal oxide of sodium-ion batteries (SIBs) has a high specific capacity and has been widely studied by scientific researchers. The O3 phase NaCrO 2 (NCO) which is a kind of potential SIBs cathode material has good thermal stability and desirable safety performance. However, it suffers from complex phase transitions and rapid capacity decay during cycles. Herein, the robust dual-phase modification layer is construct on the surface of NCO to enhance its surface and interface stability. A dispersed pyrolytic carbon layer and the island LaF 3 on the surface of the materials are formed by heat treatment of NCO with PVDF and La 2 (CO 3) 3 ·8H 2 O. The effects of the modification amount on NCO structure, electrochemical performance and the capacity fading mechanisms are characterized by various methods. The results show that the surface fluorination modification not only helps to improve the conductivity of the surface of the materials by conductive carbon network and reduce the side reactions, but also enhances structural and interface stability by the stable LaF 3 decoration and lattice oxygen replacement with pyrolysis of PVDF. It is worth noting that this modification method improves the thermodynamic stability of the electrode interface by introducing a highly stable coating on the electrode and it's beneficial to improve the rate performance and cycle performance of the material. As a result, the modified NCO displays good rate capability and cycle performance with 80.86% after 900 cycles at 2 C rate, and the specific capacity is 76.7 mAh g−1 at 40 C rate. This investigation highlights the advantages of this surface modification treatment method with respect to the surface stability of NCO and suppressing phase transition. [ABSTRACT FROM AUTHOR]

Abstract: The electrodeposition of copper on pyrolytic graphite from CuSO4 or Cu(NO3)2 in a 1.8M H2SO4 aqueous solution was investigated. The Cu deposits were formed potentiostatically and characterized by electrochemical methods, scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy. It was found that the deposition of copper in the presence of CuSO4 induced the codeposition of sulfate anions. In addition, electrochemical quartz crystal microbalance revealed that the increase of the Cu mass was higher than expected from Faraday''s law with the CuSO4/H2SO4 solution. These results confirmed the specific adsorption of anions during the Cu deposition. On the other hand, the use of Cu(NO3)2 resulted in a non-contaminated surface with different surface morphologies. The Cu nuclei size, the population density and the surface coverage were monitored as a function of the deposition potential. From the analysis of the chronoamperometric curves, the nucleation kinetics was studied by using various theoretical models. Independently of the Cu source, the nucleation mechanism follows a three-dimensional (3D) process. Copper nucleates according to an instantaneous mode when the deposition potential is more negative than −300mV versus Ag/AgCl, while the nucleation was interpreted in terms of a progressive mode at −150mV. The nuclei population densities were also determined by using two common fitting models for 3D nucleation and growth (Scharifker–Mostany and Mirkin–Nilov–Heerman–Tarallo). Their values are reported here as a function of the deposition potential. [Copyright &y& Elsevier]

We have studied the electro-oxidation of thioglycolic acid (TGA) catalyzed by iron phthalocyanines and iron porphyrins (FeN4 complexes) deposited on ordinary pyrolytic graphite and on multiwalled carbon nanotubes. The purpose of this work is to establish both experimental and theoretical reactivity descriptors of MN4 macrocyclic complexes for electrooxidation of thioglycolic acid (TGA) as an extension of previous studies involving other reactions using these types of catalysts. Essentially, the reactivity descriptors are all related to the ability of the metal center in the MN4 moiety to coordinate an extra planar ligand that corresponds to the reacting molecule. This coordinating ability, represented by the M-TGA binding energy can be modulated by tuning the electron-donation ability of the ligand and it is linearly correlated with the Fe(III)/(II) redox potential of the complex. Experimental plots of activity as (log j) E at constant potential versus the Fe(III)/(II) redox potential of the MN4 catalysts give volcano correlations. A semi-theoretical plot of catalytic activities (log j) E vs DFT calculated Fe-TGA binding energies (E bTGA) is consistent with the experimental volcano-type correlations describing both strong and weak binding linear correlations of those volcanos. On the other hand, the Hirshfeld population analysis shows a positive charge on the Fe center of the FeN4 complexes, indicating that electron transfer occurs from the TGA to the Fe center in the FeN4 complexes that act as electron acceptors. The donor (TGA)-acceptor (Fe) intermolecular hardness Δ η DA was also used as reactivity descriptor and the reactivity of the Fe centers as (log j) E increase linearly as Δ η DA increases. If activity is considered per active site, the trends is exactly the opposite, i.e. a plot of (log TOF) E increases linearly as Δ η DA decreases as expected form the Maximum Hardness-Principle. A plot of (log TOF) E versus E °' Fe(III)/(II) gives a linear correlation indicating that the activity per active site increases as the redox potential decreases. [Display omitted] [ABSTRACT FROM AUTHOR]

• A chemical vapor deposition method to deposit Si uniformly on the MOF is achieved. • An ingenious core-shell structure with the outer thin carbon shell, homogeneous deposition of Si and inner porous graphitized network. • The inner porous network is favorable for the diffusion kinetics of lithium-ion. • The integrity of structure, especially the stability of the SEI film, is investigated in detail. • The CoMOF-D@Si@C composite exhibits an outstanding rate capacity and excellent ultralong cycling at a larger current density. Silicon (Si) is considered as the most promising candidate for anode materials in the next-generation lithium-ion batteries (LIBs). Regulating the morphology and structure of Si plays a vital role in alleviating the volume expansion and improving electronic conductivity. Herein, an ingenious core-shell structure (denoted as CoMOF-D@Si@C) is synthesized by depositing Si uniformly on the pyrolytic metal-organic frameworks (MOFs) via chemical vapor deposition (CVD) method and then encapsulated with a carbon shell. The CoMOF-D@Si@C exhibits excellent rate capability and cycle performance, which delivers a high-rate capability of ~957 mAh g−1 at 10 A g−1 and a reversible capacity of 1493 mAh g−1 after 400 cycles. In particular, the capacity is maintained at 648 mAh g−1 after 1200 cycles at a high current density of 4 A g−1 with a rapid increase of the Coulombic efficiency (CE) to 99.8% after only 5 cycles and the average CE (99.7%) in the whole cycling at 4 A g−1. Profiting from the outer carbon shell, uniform Si deposition and inner porous pyrolytic MOF structure, this architecture can maintain structural stability and provide constructive conductivity during cycling processes. The superior electrochemical performance of the CoMOF-D@Si@C composite makes it a promising anode material for LIBs. [ABSTRACT FROM AUTHOR]

• High performance N -doped Na 3 V 2 (PO 4) 2 F 3 /C is constructed by a PECVD technology. • Pyridinic, pyrrolic and graphitic nitrogen are generated at high energy condition. • The formation of defects on the carbon can accelerate the diffusion of sodium ions. • NVPF@N-3 delivers excellent rate, cyclic performance and structural stability. • The capacity retention of cathode NVPF@N-3 is 91.4% at 10 c after 1000 cycles. One N -doped carbon coated Na 3 V 2 (PO 4) 2 F 3 /C cathode for sodium-ion batteries was successfully prepared by a Plasma enhanced chemical vapor deposition (PECVD) method. N 2 gas is used as the nitrogen source and it is ionized to form chemically active nitrogen ion. It can easily react with the carbon atoms in sample Na 3 V 2 (PO 4) 2 F 3 /C. Research results show that the introduction of N does not affect the crystal structure of the material. The N -doped carbon layer in sample Na 3 V 2 (PO 4) 2 F 3 /C becomes more and more homogeneous. The formation of the pyridinic nitrogen, pyrrolic nitrogen and graphitic nitrogen in the carbon layer can generate additional active sites to shorten the transmission distance of sodium ions, which can improve the electrochemical performance of Na 3 V 2 (PO 4) 2 F 3 /C cathode. The NVPF@N-3 cathode treated by PECVD for 30 min displays excellent rate performance (109.8 mAh•g−1 at 5 C) and cyclic performance, in which the capacity retention after 1000 cycles at 10 C is 91.4% and the crystal structure of NVPF@N-3 is well maintained. This research demonstrates that the pyrolytic carbon in Na 3 V 2 (PO 4) 2 F 3 /C cathode for sodium-ion batteries can be effectively doped by Nitrogen through a novel PECVD technology. [Display omitted] [ABSTRACT FROM AUTHOR]

• Porous hybrid carbon was synthesized from pyrolytic plastic waste residues. • Boron and nitrogen hetero-atoms were co-doped on hybrid porous carbon surface. • The resultant carbon is used as a modified separator in lithium sulfur batteries. • The resultant cell shows a low capacity decay of 0.057% over 500 cycles at 1 C. The continuous consumption of plastic has caused plastic waste accumulation and negative impacts on the environment. In response to this issue, plastic waste recycling through a pyrolysis process to produce liquid oils has been proposed. However, the pyrolysis process involves discarded or incinerated residue and effective utilization of the pyrolytic residue is required accordingly. This work introduces a hybrid carbon material that has not only high porosity but also polar sites, such as metal oxides and multi-hetero-atom (boron and nitrogen) doping sites. This material was synthesized from pyrolytic residue through a top-down process, unlike the conventional bottom-up synthesis process employed for hybrid carbon. The resultant material is used as a functional layer of a modified separator, and it can effectively suppress the shuttle effect with excellent lithium polysulfide trapping ability and positively contribute to redox reaction kinetics of lithium sulfur batteries. As a result, a resultant cell with the pyrolytic residue derived modified separator exhibited outstanding cyclic stability and electrochemical performance: the capacity decay per cycle was only 0.057% even after 500 cycles at a current density of 1 C. This work will provide a useful reference to suggest a promising approach for effective utilization of the pyrolytic plastic waste residue. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon microelectrodes are being used extensively in numerous applications due to their intriguing and promising material properties. Here, we present the optimized fabrication of carbon nanograss (CNG) electrodes with a single-step UV lithography with SU-8 photoresist followed by maskless reactive-ion etching and pyrolysis. This simple method provides nanostructured carbon electrodes with high surface area suitable for electrochemical applications such as biosensing or electrochemical monitoring of cells. The effects of the initial SU-8 film thickness and the etching time on the electrochemical response of the electrodes was investigated using cyclic voltammetry and electrochemical impedance spectroscopy. Finally, the CNG electrodes were tested for electrochemical detection of dopamine and compared with 2D pyrolytic carbon electrodes without nanograss. The carbon electrodes with the highest CNG displayed an approximately 2-fold increase in electrochemical signals compared to the 2D electrodes due to the increase in electrode surface area. [ABSTRACT FROM AUTHOR]

• Electroanalysis of Artificially Expanded Genetic Information System (AEGIS). • Electroactivity of 8 AEGIS 2'-deoxynucleosides was described of which 1 was inactive. • Pyrolytic graphite electrode was used for reductions at highly negative potentials. • Pyrolytic graphite electrode was used for oxidations at highly positive potentials. • Newly described peaks will be later used for AEGIS base identification in DNA. Recently we showed the reduction and oxidation of six natural 2′-deoxynucleosides in the presence of the ambient oxygen using the very broad potential window of a pyrolytic graphite electrode (PGE). Using the same procedure, 2′-deoxynucleoside analogs (dNs) that are parts of an artificially expanded genetic information system (AEGIS) were analyzed. Seven of the eight tested AEGIS dNs provided specific signals (voltammetric redox peaks). These signals, described here for the first time, will be used in future work to analyze DNA built from expanded genetic alphabets, helping to further develop AEGIS technology and its applications. Comparison of the electrochemical behavior of unnatural dNs with the previously documented behaviors of natural dNs also provides insights into the mechanisms of their respective redox processes. [ABSTRACT FROM AUTHOR]

• 2D and 3D pyrolytic carbon microelectrodes were fabricated. • Gelatin hydrogels with Saos-2 cells were deposited on the electrodes. • Alkaline phosphatase activity in the 3D cell cultures was measured electrochemically. • Initial activity was higher in 3D cell cultures but decreased due to spheroid formation. • With 3D carbon microelectrodes 2-fold higher signals were recorded in the 3D cultures. In bioelectrochemistry, cells are typically cultured in monolayers on 2D electrodes and methods such as electrochemical impedance spectroscopy (EIS) or voltammetry are used to detect changes in the cell population or responses to external stimuli. Here, we implement an electrochemical assay for the in situ monitoring of alkaline phosphatase (ALP) activity of Saos-2 cells cultured in a 3D gelatin hydrogel matrix with a thickness of 300 µm deposited on pyrolytic carbon electrodes. After cell seeding, ALP activity for cells in the hydrogel was higher compared to 2D cell cultures probably due to unrestricted access to the enzyme on the complete cell membrane. Gradual decrease of cell proliferation, maturation and spheroid formation in the 3D cell culture resulted in slower increase and eventually a decrease in ALP activity over time. Finally, 3D microstructured electrodes and 3D carbon pillar microelectrodes with a height of 225 µm were fabricated and applied for ALP detection directly in the 3D cell cultures. This resulted in higher electrochemical signals compared to 2D electrode configurations due to increased electrode surface area and penetration of the microelectrodes into the cell-laden hydrogel. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The layer-wise deposition of the laser powder bed fusion (L-PBF) process offers a tailorable microstructure with anisotropic properties. This research aimed to investigate the contribution of crystallographic texture on the anisotropic electrochemical/corrosion behavior of a L-BPF processed commercially pure nickel (Ni) cube along surfaces oriented parallel and perpendicular to the building direction. In order to exclusively assess the role of crystallographic texture on the corrosion behavior, the electrochemical measurements were performed on different surfaces of the L-PBF processed cube in alkaline and acidic chloride-free solutions. Orientation microscopy analysis showed that the morphology of grains along the parallel surface to the building direction was columnar, and their crystallographic orientation distribution was uniform. In contrast, the morphology of grains on the surface aligned normal to the building direction was equiaxed and highly oriented toward [110]. This bias in the orientation distribution led to the highest residual affinity for oxidation in comparison to the other planes in the FCC (Face Centered Cubic) crystal structure. In the case of 1 M NaOH solution, the hydroxide layer formed at the exposed surface did not effectively control the cation ejection from the surface. Also, surfaces oriented normal to the building direction, with lower surface atomic density, showed an elevated dissolution rate. Conversely, in the case of 1 M H 2 SO 4 solution, a more integrated and thicker oxide film formed in comparison to the surface aligned parallel to the building direction. This fact led to reduced surface dissolution. This study shows that engineering the topology and microstructure based on the desired properties can remarkably promote the performance of additively manufactured materials in extreme environments. [ABSTRACT FROM AUTHOR]

In this work we studied the effect of carbon in LaMnO 3 - and Mn 3 O 4 - carbon composites synthesized through the In Situ Auto Combustion (ISAC) route for the Oxygen Reduction Reaction (ORR). For this study, we prepared LaMnO 3 perovskite and Mn 3 O 4 spinel composites using different types of carbon materials: carbon blacks, pyrolytic carbons, and catalytic filamentous carbon. Various analytical methods such as cyclic voltammetry, rotating ring disc electrode, Brunauer-Emmett-Teller (BET) method, X-Ray Powder Diffraction (XRD), thermogravimetric analysis (TGA), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS) were used to shed light on the influence of carbon in LaMnO 3 - and Mn 3 O 4 - carbon composites during the ORR. These allowed us to define key characteristics of carbon materials, which determine the ORR activity and selectivity of the composites, among them sub-structural characteristics of carbon materials and pore accessibility. We conclude that (i) the ISAC route allows to significantly increase the number of accessible oxide sites and the ensuing ORR activity, (ii) the oxidation degree of Mn in LaMnO 3 depends on the type and wt.% of carbon material and sub-structural order of carbon. (iii) We further claim that sub-structural characteristics of carbon materials, their pore size and size distribution affect the ORR activity of LaMnO 3 - and Mn 3 O 4 - carbon composites. (iv) We see that an optimum combination of the carbon and the metal oxide allows obtaining the highest ORR activity. (v) Vulcan XC72 carbon seems to be the best suited for the ISAC synthesis of metal oxide-carbon composites due to its high structure consisting of highly branched flexible reticulate agglomerates. [ABSTRACT FROM AUTHOR]

By applying square-wave voltammetry (SWV) and through examining the most common electrochemical kinetic region, i.e. the quasi-reversible charge transfer process, the important role of the step potential (height, Δ E) was theoretically and practically studied considering both, the dissolved as well as the electrode surface confined redox species. It was found that the impact of the step potential is readily manifested through the scan rate (v) of an SWV experiment, the one being the product of the frequency of pulses (f) and the step potential (v = Δ E f). The presented studies evidently confirmed that the role of the step potential is very complex but that it significantly affects the morphology of both, the forward as well as the backward SWV current components, which applies for any degree of electrochemical reversibility. Furthermore, it was demonstrated that in case of quasi-reversible electrochemical reactions the degree of reversibility profoundly depends on the step potential applied. Moreover, it was proven that the degree of reversibility can be markedly improved by correspondingly decreasing Δ E. This has significant importance in the context of electrode kinetics as well as in analytical applications. Hence, this study clearly demonstrated that besides the frequency, the step potential can be an additional important tool for inspecting and improving the electrode kinetics in SWV. Finally, in order to test a practical example of a quasireversible electrode reaction of a dissolved redox couple, the SWV measurements of theFe3+(aq)/Fe2+(aq) redox couple were carried out using a basal plane pyrolytic graphite electrode and the resulting readings confirmed our theoretical predictions. [ABSTRACT FROM AUTHOR]

Considerable promotion of RuO 2 hosted by perovskite-like structure of rare earth–CoO 3 composite and vice versa supercapacitive performances is reported. Spherical, sub-μm-sized, regular spheres of La 0.6 Sr 0.4 CoO 3 (LSCO), were synthesized by ultrasonic spray pyrolysis. The sphere surface was subsequently hydrothermally doped by RuO 2. LSCO and LSCO/RuO 2 composites were investigated for their supercapacitive performances in alkaline solution. Microstructure and surface morphology were studied by SEM and XRD. It was found that amorphous Ru species decorate LSCO surface, and possibly incorporate partially into B-site of the LSCO lattice. Electrochemical characterization by cyclic voltammetry (CV), galvanostatic charge-discharge (G-C/DC) and electrochemical impedance spectroscopy (EIS) clearly revealed that capacitive performances of LSCO are considerably improved by addition of 20 mass. % of RuO 2. The registered capacitance for LSCO/RuO 2 reaches the values of pure RuO 2 , which reveals the promoting influence of LSCO on RuO 2 pseudocapacitance. The EIS analysis showed that RuO 2 catalyzes the redox transition of Co species, with simultaneous proportional increase in pseudocapacitive RuO 2 abilities while being hosted by LSCO. This intrinsic interactive promotion introduces LSCO/RuO 2 composite as unique supercapacitive material. G-C/DC curves showed that LSCO/RuO 2 is of modest cyclability with respect to pure LSCO and RuO 2 , although the capacitance losses with cycling are acceptably low. Image 1 • Microspheres of La 0.6 Sr 0.4 CoO 3 (LSCO) synthesized via single step USP technique. • Promotion of supercacitive performances of RuO 2 hosted by LSCO and vise versa. • RuO 2 nanoparticles supported on LSCO surface with the size around 2–3 nm. • Sr replacement by Ru in LSCO/RuO 2 leads to higher rates of redox reactions. • Long-term cyclability LSCO/RuO 2 appears to be less sensitive than LSCO. [ABSTRACT FROM AUTHOR]

Carbon materials are widely applied as conductive additives in studies of the oxygen evolution reaction (OER) in alkaline media catalyzed by transition metal oxides. In this work we investigate the anodic behavior of three representative carbon materials: furnace black (Vulcan XC-72R), acetylene black, and pyrolytic carbon of the Sibunit family (Sibunit-152), in 1 M NaOH at high potentials (ranging from the OER onset and up to ca. 2 V vs. RHE) in the time span from several minutes to several hours. We apply the rotating ring-disk electrode (RRDE) to separate the OER current from the carbon corrosion current. We then use transmission electron microscopy (TEM) to visualize changes in the carbon morphology resulting from corrosion. Finally, we study the OER performance of composite electrodes comprising carbon materials mixed with a La 0.5 Sr 0.5 Mn 0.5 Co 0.5 O 3−δ perovskite OER catalyst, and discuss possible influence of the oxide on the carbon corrosion. [ABSTRACT FROM AUTHOR]