Standard Calomel Electrode Research Articles

Comparison between Corrosion of Stainless Steel Hand k-file and Nickel-Titanium Rotary Instrument following Immersion in 5.25% NaOCL Irrigation Solution: An In Vitro Study

The study was aimed to compare the corrosion of stainless-steel hand K-file and Nickel-titanium rotary instrument following immersion in 5.25% NaOCL irrigation solution, in vitro. A total of 20 new Nickel-titanium (NiTi) rotary files and 20 stainless steel (K file) was selected and immersed in 5.25% NaOCL irrigation solution. All files were subjected to the corrosion test: Record the open circuit potential (OCP) for 1 h on a strip chart with high impedance. The strip chart recording for each file was classified into a stability score: (i) stable, (ii) unstable, or (iii) erratic. The percentage of OCP was measured by a potentiostat and a standard calomel electrode reference. The frequencies of visually observed corrosion were further investigated by scanning electron microscope (SEM). The results of the present study confirmed that stainless steel file showed greater corrosion rate than that of NiTi files. Additionally, both files had pitting and crevice corrosion, as seen by scanning electron microscopy (SEM) analysis. However, NiTi files demonstrated a lower rate of corrosion than stainless steel files. In conclusion, NiTi files showed greater corrosion resistance than that of stainless-steel files.

Unveiling optimal half-cell potentials in RCC slabs through cutting-edge ANFIS, ANN and genetic algorithm integration

PurposeThe purpose of this study is to compare the prediction models for half-cell potential (HCP) of RCC slabs cathodically protected using pure magnesium anodes and subjected to chloride ingress.The models for HCP using 1,134 data set values based on experimentation are developed and compared using ANFIS, artificial neural network (ANN) and integrated ANN-GA algorithms.Design/methodology/approachIn this study, RCC slabs, 1000 mm × 1000 mm × 100 mm were cast. Five slabs were cast with 3.5% NaCl by weight of cement, and five more were cast without NaCl. The distance of the point under consideration from the anode in the x- and y-axes, temperature, relative humidity and age of the slab in days were the input parameters, while the HCP values with reference to the Standard Calomel Electrode were the output. Experimental values consisting of 80 HCP values per slab per day were collected for 270 days and were averaged for both cases to generate the prediction model.FindingsIn this study, the premise and consequent parameters are trained, validated and tested using ANFIS, ANN and by using ANN as fitness function of GA. The MAPE, RMSE and MAE of the ANFIS model were 24.57, 1702.601 and 871.762, respectively. Amongst the ANN algorithms, Levenberg−Marquardt (LM) algorithm outperforms the other methods, with an overall R-value of 0.983. GA with ANN as the objective function proves to be the best means for the development of prediction model.Originality/valueBased on the original experimental values, the performance of ANFIS, ANN and GA with ANN as objective function provides excellent results.

Exploring the Potential of α-MnO<sub>2</sub>/ Carbon Nanotubes for Improved Oxygen Reduction Reaction Performance at the Cathode of Alkaline Fuel Cells

In the field of fuel cell technology, the development of cost-effective catalysts is crucial for the commercialization of Alkaline Membrane Fuel Cells (AMFCs). Platinum (Pt) has traditionally been employed as the catalyst in AMFCs, but its high cost poses a major barrier to widespread adoption. In this study, a new catalyst material was developed by incorporating Manganese Dioxide (α-MnO2) into Carbon Nanotubes (CNTs) using hydrothermal synthesis techniques. The synthesized catalyst was characterized using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD), and its electrocatalytic activity was evaluated through Linear Sweep Voltammetry (LSV) and CV through Rotating Disc Electrode (RDE) experiments. The results showed that the α-MnO2-CNT composite displayed strong durability in the alkaline environment and high electrocatalytic activity for oxygen reduction reaction (ORR). The LSV measurements revealed a current density of -4.1 mA/cm2 and an overpotential of -0.3V relative to Standard Calomel Electrode (SCE) in a 0.1M KOH electrolyte. Additionally, the α-MnO2-CNT composite displayed high methanol tolerance and long-term stability compared to commercial Pt/C catalysts. This study demonstrates that the use of α-MnO2-CNT as a cost-effective alternative to Pt has the potential to facilitate the commercialization of AMFC technology.

Analysis of Photocatalytic Properties of Titanium Dioxide Electrode Supported By Hydroxyapatite Co-Catalyst in a Marine Solar Cell

Titanium dioxide (TiO2), as an n-type semiconductor photocatalyst, has been widely studied and used in many environmental and energy applications such as solar cells, wastewater treatment, air purification, water splitting for hydrogen production and CO2 conversion due to its superior electrical and optical properties, stability, and biocompatibility. Using its photocatalytic and other properties, we have been studying a floating photoelectrochemical cell that can be applicable to the marine environments. This cell is designed to utilize titanium dioxide as its photoanode and copper oxides photocathode, and seawater is used as an electrolyte between electrodes. The drawbacks of using titanium dioxide as photocatalysts are its high electron-holes recombination rates and lower absorption efficiency in visible light regions. To improve against these drawbacks, we studied hydroxyapatite (HAp, Ca10(PO4)6(OH)2) as co-catalyst for titanium dioxide electrode. Since HAp possesses biocompatibility, it is suitable to be used with TiO2 electrode in marine environments. In previous studies, it was found that HAp improved and boosted the current density produced by the titanium dioxide electrode. However, removal of HAp occurred from the surface of titanium dioxide during the photoelectrochemical measurements. Therefore, in this study, we have optimized the content of HAp paste that would be applied to the surface of titanium dioxide electrode by screen printing method.For preparation of titanium dioxide electrode, type 329J4L stainless steel was selected as the base substrate. Firstly, surface of the substrate was grinded to form the grid pattern and cleaned with ethanol in ultrasonic cleaner and then with distilled water. After that, the substrate was passivated with 10 % HNO3 at 60 ºC for 30 minutes. The passivated substrate was then printed and heat treated with TiO2 paste twice at 150 ºC for 1 hour and 550 ºC for 30 minutes respectively. Double layered titanium dioxide electrode was then printed with HAp paste and heat treated at 150 ºC for 1 hour. To check the characteristics of photocatalytic effect of electrode, photopotential and potentiodynamic polarization measurements were performed to the electrode. For illumination test, xenon light with an intensity of 10.5 mW/cm2 and a calibrated wavelength of 250-800 nm was used as the light source. The measurement was conducted in artificial seawater as the controlled electrolyte. Standard calomel electrode (SCE) was used as a reference electrode and platinum electrode as a counter electrode. The measurement was performed both with and without irradiated conditions. The microstructures and surface morphology of electrode before and after electrochemical measurements were analyzed and examined by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD).The results show optimized HAp also improve the photocatalytic activities of n-type semiconductor titanium dioxide. In previous study, removal of HAp was considered due to the addition of carboxymethyl cellulose (CMC) as a viscosity modifier to HAp paste. CMC possess higher hydration rate which may cause rapid agglomeration when it is introduced to water. Although it has satisfactory quality to control the viscosity of the paste, rapid hydration cause removal of HAp after the electrode was heat treated and measurement was performed in artificial seawater. In this study, polyethylene glycol (PEG) was used as the viscosity modifier for HAp paste and Triton-X-100 was used as the surfactant to control the surface tension of the paste. As a result, HAp paste was produced to be screen-printable onto the surface of TiO2 electrode and removal of HAp was minimized compared to the previous study. Moreover, HAp became a good sorbent and co-catalyst for titanium dioxide electrode in its photocatalytic activities.

Electrochemical synthesis of reduced graphene oxide and their anti-corosion properties

Reduced graphene oxide (Gr) has been synthesized electrochemically on the surface of copper metal at a fixed potential of 1.5 V versus a standard saturated calomel electrode (SCE). The synthesized Gr was then characterized with X-Ray diffraction, thermogravimetric analysis, raman and Fourier transform infrared (FT-IR) spectroscopies. The anti-corrosion behavior of Gr was tested with polarization measurements and electrochemical impedance spectroscopy (EIS) in acidic medium of 0.5 M sulfuric acid solution. X-ray difraction (XRD), thermogravimetric analysis (TGA), and Raman analyses revealed that the Gr is more thermo-stable than GO. The d-spacing between sheets in comparison Gr (~ 3.78 Å) is shorter than d-spacing between sheets in GO (~ 8.80 Å). The Gr film synthesized within 30 seconds shows the better anti-corrosion behavior in comparison to the films synthesized with longer time interval.

Synthesis of MnO2 Carbon nanotubes catalyst with enhanced Oxygen Reduction Reaction for Polymer Electrolyte Membrane Fuel Cell

Polymer Electrolyte Membrane Fuel Cell (PEMFC), an electrochemical power generating technology, uses a precious metal Platinum (Pt) catalyst for Oxygen Reduction Reaction (ORR), which is a major hindrance in its commercialization. Using a non-precious group metal (NPGM) instead of Pt will reduces the cost of PEMFCs. Herein MnO2 carbon nanotubes (CNTs) were synthesized by impregnating the transition metal in large surface carbonaceous material CNTs by hydrothermal synthesis techniques. To enhance the catalytic reaction and increase the volumetric current density, the sample was pyrolyzed at 800 0C temperature under nitrogen atmosphere. During pyrolysis, the nitrogen was also doped in the framework of carbonaceous materials. The materials were then treated with acid, removing the unreacted metals and adding oxygen functional group to the CNT framework due to which the activity of the catalyst is amplified. The catalysts have been characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Catalyst activity has been calculated by Rotating Disc Electrode (RDE) experiment. The resulting materials are stronger in experimental conditions in alkaline environment and have high electro catalytic activity for oxygen reduction reaction (ORR). Linear Sweep Voltammetry (LSV) depicts a current density of - 4.0 mA/cm2 and over potential of -0.3V vs. Standard Calomel Electrode (SCE) in 0.1M KOH electrolyte. Rotating Disk Electrode (RDE) was conducted at 400, 800, 1200, and 1600 rpm. The results of MnO2CNT show a desirable future aspect in fuel cell commercialization.

Cyclic voltammetry studies of bioanode microbial fuel fells from batch culture of Geobacter sulfurreducens

The present study aims to investigate the performance of batch culture of Geobacter sulfurreducens (G. sulfurreducens) for electrical current generation via cyclic voltammetry (CV) method. The CV study was performed with an applied voltage in the range of -0.1 to 0.1 V against the standard calomel electrode (SCE) during the cell growth and attachment of G. sulfurreducens on graphite felt and initial acetate concentration of 20 mM. The kinetics of electrode reaction was investigated by conducting CV experiments at different scanning rates of 5, 10, 20, 50 and 100 mVs -1. The diffusion coefficients (D) and heterogeneous electron transfer rate constant (k o) of both anodic and cathodic process were 1.04×10 -5 cm 2·s -1, 1.73×10 -6 cm 2.s -1, 0.0004 cm.s -1 and 0.0011 cm.s -1, respectively. The obtained results showed that the anode exhibits high bioeletrocatalytic activity due to the attachment of G. sulfurreducens on the anode surface.

Mesoionic carbene-Breslow intermediates as super electron donors: Application to the metal-free arylacylation of alkenes

Classical N-heterocyclic carbenes (NHCs), such as thiazolylidenes, 1,2,4-triazolylidenes, and imidazol(in)-2-ylidenes, are powerful organocatalysts for aldehyde transformations through the so-called Breslow intermediates (BIs). The reactions usually occur via electron-pair-transfer processes. In contrast, the use of BIs in single-electron transfer (SET) pathways is still in its infancy, and the scope is limited by the moderate reduction potential of BIs derived from classical NHCs (ca. −1.0 V versus standard calomel electrode [SCE]). Here, we report that BIs from 1,2,3-triazolylidenes, a type of mesoionic carbene (MIC), have a reduction potential as negative as −1.93 V versus SCE and thus are among the most potent organic reducing agents reported to date. They are reductive enough to undergo SET with iodoarenes, which allows the highly efficient inter- and intramolecular MIC-catalyzed arylacylation of styrenes and alkenes, respectively.

Bismuth vanadate photoanodes for water splitting deposited by radio frequency plasma reactive co-sputtering

Photoactive bismuth vanadate (BiVO4) thin coatings were deposited on fluorine-doped tin oxide glass by plasma reactive sputtering from Bi2O3 and vanadium (V) radio frequency (RF) powered targets. The films were characterized by x-ray diffraction, scanning electron microscopy, energy dispersion spectroscopy, and UV-vis spectroscopy. The effects that the power density supplied to the Bi2O3 target, the post-annealing treatment, and the film thickness have on the structural features and on the photoelectrochemical (PEC) performances of the so obtained BiVO4 film-based photoelectrodes were investigated. Their PEC performance in water splitting was evaluated in a three-electrode cell by both incident photon to current efficiency and linear sweep voltammetry measurements under AM 1.5 G simulated solar light irradiation. A monoclinic phase of BiVO4, which is more photoactive than the tetragonal BiVO4 phase, was obtained by optimizing the power density supplied to the Bi2O3 target, i.e., by tuning the Bi:V:O atomic ratio. The best PEC performance was obtained for a stoichiometric 1:1 Bi:V atomic ratio, attained with 20 W power supplied to the Bi2O3 target and 300 W power supplied to the vanadium target, and an optimal 200 nm thickness of the BiVO4 film, with a 0.65 mA/cm2 photocurrent density attained at 1.23 V versus standard calomel electrode, under simulated solar light. These results show the suitability of plasma reactive sputtering with two RF powered electrodes for the deposition of BiVO4 photoanodes for water splitting.

Asymmetric supercapacitors by integrating high content Na+/K+-inserted MnO2 nanosheets and layered Ti3C2Tx paper

In this work, Na+/K+- inserted MnO2 (NaxKyMnO2) nanosheets are synthesized on Ni foam via a facile and efficient route based on an electro-deposition and electro-oxidation reaction process. The NaxKyMnO2 nanosheet arrays has a broad potential window, which can be extended to 1.0 V versus standard calomel electrode (vs. SCE). The NaxKyMnO2 with iso-oriented feature and unique nanoarchitectures provides shortened diffusion path lengths for both Na+, K+ and electronic transport, and reduces the stress associated with Na+, K+ insertion and extraction. The layered Ti3C2Tx paper on Ni foam (Ti3C2Tx@NF) are also synthesized successfully that can act as a negative electrode, stably in a negative potential window of −0.8−0 V (vs. SCE). Subsequently, an aqueous asymmetric supercapacitor is demonstrated with a high potential of 1.8–2.0 V by using NaxKyMnO2@NF as the positive electrode and Ti3C2Tx@NF as the negative electrode. The asymmetric device achieves a high power density of 9.396 mW/cm2 and improved energy density of 0.11 mWh/cm2, as well as great cycling performance.

Copper-Tin Alloys for the Electrocatalytic Reduction of CO2 in an Imidazolium-Based Non-Aqueous Electrolyte

The ability to synthesize value-added chemicals directly from CO2 will be an important technological advancement for future generations. Using solar energy to drive thermodynamically uphill electrochemical reactions allows for near carbon-neutral processes that can convert CO2 into energy-rich carbon-based fuels. Here, we report on the use of inexpensive CuSn alloys to convert CO2 into CO in an acetonitrile/imidazolium-based electrolyte. Synergistic interactions between the CuSn catalyst and the imidazolium cation enables the electrocatalytic conversion of CO2 into CO at −1.65 V versus the standard calomel electrode (SCE). This catalyst system is characterized by overpotentials for CO2 reduction that are similar to more expensive Au- and Ag-based catalysts, and also shows that the efficacy of the CO2 reduction reaction can be tuned by varying the CuSn ratio.

Reclaimed Carbon Fiber-Based 2.4 V Aqueous Symmetric Supercapacitors

Carbon fiber (CF) is a promising material as carbon-based electrode and support for flexible supercapacitors. However, it still suffers from narrow voltage in the aqueous electrolyte due to the water decomposition (1.23 V). Herein, an aerobic pyrolysis is developed to recover aligned carbon fibers from carbon fiber reinforced polymers. More importantly, during this oxygen existence condition, the surface of reclaimed carbon fibers (RCFs) is etched into groove-shaped structure and modified by introducing abundant oxygen-containing functional groups, which significantly expands the negative potential window of RCFs-based electrode to −1.4 V (vs standard calomel electrode) and the working voltage of RCFs-based symmetric supercapacitor to 2.4 V in an aqueous electrolyte of 1.0 M Na2SO4, with capacitance retention of 90% and 93.6% after 10 000 cycles, respectively. This work well matches the aerobic pyrolysis of recovery of CFs from CFRPs and electrochemical performances of RCFs, supplying a new strategy to de...

Microwave-assisted hydrothermal synthesis and electrochemical characterization of niobium pentoxide/carbon nanotubes composites

Abstract

DEVELOPMENT OF A SENSOR BY ELECTRO-POLYMERIZATION OF ERICHROME BLACK-T ON GLASSY CARBON ELECTRODE AND DETERMINATION OF AN ANTI-INFLAMMATORY DRUG DICLOFENAC

Objective: The aim of this study was to develop a simple, reliable voltammetric method and its validation for determination of nonsteroidal anti-inflammatory drug diclofenac (DFC).
 Methods: The proposed method was based on electro-oxidation of DFC at poly (erichrome black T) modified glassy carbon electrode (PEBT/GCE) in 0.2 M phosphate buffer solution of pH 7.0. Cyclic voltammetry and differential pulse voltammetric techniques were employed to study electro-oxidation behavior. Under the optimal conditions, variations of EBT concentration, effect of pH, scan rate on the oxidation of DFC was studied.
 Results: A well-defined oxidation peak at about +0.59 V vs. standard calomel electrode was observed for voltammetric detection of DFC. pH effect shows the participation of an equal number of protons and electrons in the mechanism. The relation between a logarithm of peak current with the logarithm of scan rate indicated adsorption controlled behavior of electrode process. Concentration variations show a good linear response in the range 0.05 µM to 40 µM with the detection limit of 5.25 × 10-8 M.
 Conclusion: The prepared sensor exhibited good selectivity, sensitivity, and stability for the detection of DFC in the pharmaceutical dosage form and real samples. The developed method could possibly be adopted for pharmacokinetic studies and also in clinical and quality control laboratories where time and economy were important.

Low-Loading of Pt Nanoparticles on 3D Carbon Foam Support for Highly Active and Stable Hydrogen Production.

Minimizing Pt loading is essential for designing cost-effective water electrolyzers and fuel cell systems. Recently, three-dimensional macroporous open-pore electroactive supports have been widely regarded as promising architectures to lower loading amounts of Pt because of its large surface area, easy electrolyte access to Pt sites, and superior gas diffusion properties to accelerate diffusion of H2 bubbles from the Pt surface. However, studies to date have mainly focused on Pt loading on Ni-based 3D open pore supports which are prone to corrosion in highly acidic and alkaline conditions. Here, we investigate electrodeposition of Pt nanoparticles in low-loading amounts on commercially available, inexpensive, 3D carbon foam (CF) support and benchmark their activity and stability for electrolytic hydrogen production. We first elucidate the effect of deposition potential on the Pt nanoparticle size, density and subsequently its coverage on 3D CF. Analysis of the Pt deposit using scanning electron microscopy images reveal that for a given deposition charge density, the particle density increases (with cubic power) and particle size decreases (linearly) with deposition overpotential. A deposition potential of −0.4 V vs. standard calomel electrode (SCE) provided the highest Pt nanoparticle coverage on 3D CF surface. Different loading amounts of Pt (0.0075–0.1 mgPt/cm2) was then deposited on CF at −0.4 V vs. SCE and subsequently studied for its hydrogen evolution reaction (HER) activity in acidic 1M H2SO4 electrolyte. The Pt/CF catalyst with loading amounts as low as 0.06 mgPt/cm2 (10-fold lower than state-of-the-art commercial electrodes) demonstrated a mass activity of 2.6 ampere per milligram Pt at 200 mV overpotential, nearly 6-fold greater than the commercial Pt/C catalyst tested under similar conditions. The 3D architectured electrode also demonstrated excellent stability, showing <7% loss in activity after 60 h of constant current water electrolysis at 100 mA/cm2.

Durable and Cost Effective Oxygen Electrode Prepared By Electrodeposition for Proton Exchange Membrane Water Electrolyzer (PEMWE)

Hydrogen gas has been regarded as future energy medium for the zero-carbon, hydrogen-based energy ecosystem. For decades, however, majority of hydrogen gas (96%) has been produced by petrochemical processes that emit CO2 into atmosphere. As an effort to facilitate carbon-free energy ecosystem, the water electrolysis (WE), a technology to split water into hydrogen and oxygen using renewable sources, has been received much attention. Currently, alkaline water electrolyzer (AWE) has dominated the commercial market due to its technical maturity that provides low price. However, the drawbacks such as a need for large-scale plant and the use of toxic solvent has limited its further application on small size WE. As an alternative, the proton exchange membrane water electrolyzer (PEMWE) has been researched and recently commercialized. Advantages of this technology include compact design, high energy efficiency and high H2 purity, which is suitable to small- and medium-scale electrolyzer (<300 kW). PEMWE running at high temperature (100-150℃), also referred as to high temperature PEMWE (HT-PEMWE) is beneficial in both thermodynamic and kinetic points of views relative to conventional PEMWE (60–90℃). The better cell efficiency is associated with fast electrode reactions due to better electrode kinetics and lower equilibrium voltages. The drawbacks of high temperature operation is relatively inferior cell stability resulting from high operating temperature, which inevitably increases the stack replacement cost. The cell is severely degraded during HT-PEMWE operation, and the degradation rate become faster when the operating temperature increases. One of the major degradation source is a contact loss between IrO2 and Ti DL. The recent studies showed that Ti is rapidly passivated and corroded at high temperature (>100℃) and anodic potential (>1.0 VSHE). This process would severely degrade the DL and BP, though the impact of Ti corrosion has not been experimentally explored yet. In this study, electrodeposited IrO2 is suggested as a corrosion-protective film that suppresses the passivation of the inner Ti substrate, while also acting as a cost-effective catalyst layer for OER. An IrO2 film of submicron thickness was uniformly deposited over the entire surface of porous Ti mesh via anodic electrodeposition. The properties of the IrO2 film were examined and the performance and stability of this electrode were assessed at the single-cell level. Membrane electrode assembly (MEA) was prepared by placing the oxygen (IrO­2/Ti mesh) and hydrogen electrodes (Pt/C) onto either sides of nafion membrane (NR-212, Dupont). Oxygen electrode was prepared via anodic electrodeposition of IrO2 onto porous Ti diffusion layer in the bath of 10 mM iridium chloride hydrate (IrCl4H2O), 100 mM hydrogen peroxide H2O2, 40 mM oxalic acid (COOH22H2O, 340 mM potassium carbonate (KCO3). Ti mesh and standard calomel electrode (SCE) were employed as counter and reference electrodes, respectively. Hydrogen electrode was prepared via spraying the catalyst ink composed of 46.5wt% Pt/C (Johnson Matthey), 5 wt% nafion solution, isopropyl alcohol (IPA, J.T. Baker), and deionized water on commercial carbon paper (39BC, SGL carbon). As shown in Fig. 1, electrodeposited IrO2 film played dual roles as not only the catalyst layer toward oxygen evolution reaction (OER) but also the corrosion-protection layer preventing inner Ti from oxidation. The e-IrO2/Ti resulted in high performance (0.97 A/cm2) despite low IrO2 loading (0.4 mg/cm2) in single cell test conducted at 1.6 V and 120oC, which was comparable to that of conventional electrodes with more catalyst loading. Furthermore, the corrosion polarization test revealed that the coated IrO2 film physically blocked the exposure of Ti diffusion layer, and thus reduced the corrosion of Ti in acidic condition. Therefore, the low degradation rate (1.5 mA/cm2-hr (0.11 %/hr)) was obtained in aging experiment at 120℃ and 1.72 V (voltage efficiency : 85%), confirming the excellent stability of this electrode. Figure 1

Cathodic Protection of Steel Reinforcement using Pure Magnesium Anode

Cathodic Protection to the embedded steel in concrete was established using sacrificial pure magnesium anode to prevent the corrosion of reinforcement. Two slabs were casted one containing 3.5% sodium chloride with respect to weight of cement and the other without NaCl. Both the slabs were provided with cathodic protection of pure Magnesium anode. Half cell potential measurements with Standard Calomel Electrode as reference electrode were taken at regular intervals and for a number of days. It could be observed that the potential of the slab decreased with increase in distance from the anode and reduced with time. Thus, magnesium anode was found to shift the potential of steel to more negative potential initially and later towards less negative potentials with respect to time. It could be concluded that use of Magnesium anode could prove to be an effective means of corrosion prevention.

Catalytic performance of hybrid Pt@ZnO NRs on carbon fibers for methanol electro-oxidation

Abstract A novel Pt@ZnO nanorod/carbon fiber (NR/CF) with hierarchical structure was prepared by atomic layer deposition combined with hydrothermal synthesis and magnetron sputtering (MS). The morphology of Pt changes from nanoparticle to nanorod bundle with controlled thickness of Pt between 10 and 50 nm. Significantly, with the increase of voltage from 0 to 0.6 V (vs. standard calomel electrode), the prompt photocurrent generated on ZnO NR/CF increases from 0.235 to 0.725 mA. Besides, the Pt@ZnO NR/CF exhibited higher electrochemical active surface area (ECSA) value, better methanol oxidation ability and CO tolerance than Pt@CF, which demonstrated the importance of the multifunctional ZnO support. As the thickness of Pt increasing from 10 to 50 nm, the ECSA values were improved proportionally, leading to the improvement of methanol oxidation ability. More importantly, UV radiation increased the density of peak current of Pt@ZnO NR/CF towards methanol oxidation by additional 42.4%, which may be due to the synergy catalysis of UV light and electricity.

Photopotential and Polarization Characteristics of Ruthenizer Complex Sensitized TiO2 Electrode for Marine Microbial Fuel Cell

We have been studied the performance of TiO2 electrode which is assembled in Marine Microbial Fuel Cell (MMFC). To increase the performance of TiO2 electrode and to improve conversion efficiency from solar energy, dye sensitizing was introduced to TiO2 electrode. The dye used for this experiment is a Ruthenizer complex, Di-tetrabutylammonium cis- bis (isothiocyanato) bis (2, 2-bipyridyl-4, 4’-dicarboxylato) ruthenium (II), well known as N719 dye, which shows high reproducibility and stability performance in dye-sensitized solar cells (DSSC). We also tried forming of Hydroxyapatite (HAp) layer on TiO2 surface before dye sensitizing for the purpose of anchorage effect of dye on TiO2 surface. The measurement of photopotential and polarization property were carried out in the artificial seawater as an electrolyte which does not include the redox couple as a mediator. Photopotential and polarization was measured with a standard calomel electrode (SCE) as a reference electrode under the irradiation of a 150 W Xenon Lamp, and a platinum electrode was used as a counter electrode for polarization curve. In the measurement of photopotential, the potential dropped to active direction when the light was turned on. Once it reached to the most active potential value, it went back to noble direction slightly for 5 to 15 minutes after the light was on. The change in photopotential after that duration became small and it tended to be stable for 2 hours. This behaviour of photopotential was similar in all measurement of test electrodes. The amount of Ruthenizer after 2-hour measurement of photopotential became relatively smaller compared to that before measuring. This is because dye recombination with TiO2 electrons took place with artificial seawater electrolyte in the absence of a redox couple for dye regeneration. But, the photopotential of dye-sensitized TiO2 electrode with HAp layer showed more active than that without HAp. This showed good compatibility of HAp since it did not disturb the performance of photo-catalytic reaction of TiO2 and it may show the ion or electron selectivity between Ruthenizer and TiO2 phases. The polarization measurement showed no distinct effectiveness of Ruthenizer sensitizing on TiO2 surface other than suppressing the TiO2 photo-catalytic reaction. As the results, Ruthenizer sensitizing on TiO2 electrode showed lower photo-catalytic effect by the recombination of oxidized Ruthenizer electron due to absence of a redox mediator. On the other hand, using HAp on TiO2 electrode for Ruthenizer sensitizing showed improvement in photopotential characteristics of TiO2 electrode.

Protection of hot subsea risers by using thermally sprayed aluminium

PurposeIn spite of the high interest in thermally sprayed aluminium (TSA) to protect offshore structures, pipelines, risers, etc., data correlating the exposure of TSA-coated steel in hot seawater to its performance are lacking. No information is available on the performance of TSA in hot seawater, especially when damaged. This paper aims to address this knowledge gap and report the corrosion performance of damaged TSA on carbon steel exposed to boiling synthetic seawater for different periods (up to 5,000 h). It also attempts to understand the mechanism of formation of calcareous deposits in boiling synthetic seawater by using various characterisation tools.Design/methodology/approachTwin wire arc spray was used to coat carbon steel specimens with commercially pure aluminium. Holiday was drilled on the coated surface to expose the underlying steel, amounting to 4 per cent of the specimen surface area. These specimens were then exposed to boiling synthetic seawater for different periods: 2, 68, 188, 335 and 5,000 h. During exposure, the potential was monitored (vs standard calomel electrode [SCE]) and linear polarisation resistance (LPR) method was used to calculate the corrosion rate (CR). After exposure, these specimens were analysed by using characterisation tools such as X-ray diffraction (XRD) and scanning electron microscope (SEM)/energy-dispersive X-ray spectroscopy (EDX).FindingsThe TSA-coated steel samples with 4 per cent holiday showed a CR of approximately 0.008-0.015 mm y−1 and a stable potential (Ecorr) around −800 mV (SCE), when exposed to boiling synthetic seawater for approximately 5,000 h. Microstructural characterisation established that the deposits comprised brucite [Mg(OH)2] only (this is very different to what has been reported at ambient temperatures). The stable potentials obtained after 5,000 h suggest that the brucite layers provided effective corrosion mitigation. Thus, TSA seems to show the potential to protection hot carbon steel risers, even when damage exposing the external steel surface to the seawater is present.Originality/valueThe mechanism of calcareous deposit formation has been studied for many years, but most of the previously reported studies concentrate on low or ambient temperature behaviour. The reported studies mainly concentrate on the application of cathodic protection, rather than the effect of TSA. This is the first journal paper where the behaviour of damaged TSA in boiling synthetic seawater has been reported. The formation of brucite-only layer in the damaged area adjacent to the steel surface in boiling synthetic seawater is novel. And the mechanism of formation of this layer has been explained in the paper.