Semitransparent organic photovoltaic cell with carbon nanotube-sheet anodes and Ga-doped ZnO cathodes

We demonstrate a semitransparent organic photovoltaic (OPV) cell with two transparent electrodes: a multi-wall carbon nanotube (MWCNT) sheet and a Ga-doped ZnO (GZO) are used as a transparent anode and cathode, respectively. As an active layer, we used a bulk heterojunction structure with poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). The photovoltaic cell has a GZO/P3HT:PCBM/poly(3,4-ethylene-dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/MWCNT/PEDOT:PSS structure. For comparison, an OPV cell with a MWCNT-sheet anode and an indium tin oxide (ITO) cathode were also fabricated. The OPV cell with the GZO cathode showed better performance than that with the ITO cathode, owing to the lower work function of the former. The semitransparent OPV cell with GZO cathode demonstrated a short-circuit current of 3.4 mA/cm², open-circuit voltage of 0.51 V, and efficiency of 0.45%.     

Research on Electrochemical Behavior of Ti-Ir-Ru Anode Coating in Electrolytic Antifouling of Flowing Brine

By electrochemical techniques, the electrochemical behavior of Ti-Ir-Ru anode coating was studied in electrolytic antifouling of flowing brine. The effect of the brine’s flow rate and the anode/cathode interval on electrolysis was also considered. The results indicated that the brine’s flow rate had remarkable effect on the characteristic of the Ti-Ir-Ru anode. The electrolytic voltage and the evolved active chlorine concentration of Ti-Ir-Ru anode increased with increasing flow rate. Its energy consumption displayed the same variable rule as the electrolytic voltage. But the current density reduced with increasing flow rate. Increasing flow rate favored attenuation of the thickness of mass-transfer control layer and expediting the oxygen’s mass transfer, which accelerated the cathode polarization and the oxygen absorption reaction. The maximal current efficiency for Ti-Ir-Ru anode was obtained at the anode/cathode interval of 5 cm with the current density of 60 mA/cm². At this point, Ti-Ir-Ru anode also had relatively low electrolytic voltage. The above operating procedure was ideal for electrolyzing flowing brine using Ti-Ir-Ru anode coating.     

Fabrication and study on Ni1−xFexO-YSZ anodes for intermediate temperature anode-supported solid oxide fuel cells

Bimetal oxides Ni_1−xFe_xO (x = 0.01, 0.04, 0.08, 0.1, 0.15, 0.2, 0.4, 0.5) were synthesized and studied as anodes for intermediate temperature solid oxide fuel cells (SOFCs) based on yttria-stabilized zirconia (YSZ) film electrolyte. A single cell consisted of Ni_1−xFe_xO-YSZ anode, YSZ electrolyte film, LSM–YSZ composite cathode was prepared and tested at the temperature from 600 °C to 850 °C with humidified hydrogen (75 ml min⁻¹) as fuel and ambient air as oxidant. It was found that the cell with Ni_0.9Fe_0.1O-YSZ anode showed the highest power density, 1.238 W cm⁻² at 850 °C, among the cells with different anode composition. The promising performance of Ni_1−xFe_xO as anode suggests that bimetal anodes are worth studied for SOFCs in future.     

Manufacturing of high performance solid oxide fuel cells (SOFCs) with atmospheric plasma spraying (APS)

The potential of atmospheric plasma spraying (APS) technology has been investigated for the manufacture of anode, electrolyte and cathode of a solid oxide fuel cell. As the substrate a tape-casted FeCr alloy was used. It turned out that all layers can be applied by this technique, however, the APS cathode layer, although applied by suspension plasma spraying led to cells with rather low performance. Much better cell characteristics could be obtained by using screen-printed LSCF cathodes, which do not need any additional thermal treatment.Anode layers with high electrochemical activity were produced by separate injection of NiO and YSZ powders. The manufacturing of gastight electrolyte layers was a key-issue of the present development. As APS ceramic coatings typically contain microcracks and pores their leakage rate is not sufficiently low for SOFC applications.Based on the understanding of the formation of defects during spraying an optimized spraying process was developed which led to highly dense coatings with the appearance of a bulk, sintered ceramic. Open cell voltages above 1 V proofed the low leakage rates of the rather thin (< 50 μm) coatings. With these cells having a screen-printed cathode an output power of 500 mW/cm² could be achieved at 800 °C.It turned out that the long-term stability of the metal substrate based APS SOFCs was rather poor. The aging of the cells was probably due to interdiffusion of anode and substrate material. Hence, diffusion barrier was applied by APS between substrate and anode. These layers were very effective in reducing the degradation rate. For these cells the output power reached 800 mW/cm².     

Determination of trace mercury in compost extract by inhibition based glucose oxidase biosensor

A novel inhibition based biosensor of glucose oxidase(GOx) for environmental mercury detection was developed. An electropolymerized aniline membrane was prepared on a platinum electrode containing ferrocene as electron transfer mediator, on which GOx was cross-linked by glutaraldehyde. The response of the sensor was based on the current reduction in the electrochemical system by inhibition of mercury against GOx electrode. The detection limit of the inhibition-based sensor for mercury is 0.49 μg/L, and the linear response ranges are 0.49-783.21 μg/L and 783.21 μg/L-25.55 mg/L. The GOx membrane can be completely reactivated after inhibition, and remains 70% of the activity in more than one month. The sensor was used for mercury determination in compost extract with good results.     

Photovoltaic and impedance spectroscopy analysis of p–n like junction for dye sensitized solar cell

A dye-sensitized solar cell based on nanostructure TiO₂ and PCBM:P3HT blend was fabricated and the photovoltaic and impedance spectroscopy properties of the solar cell were investigated. The solar cell gives a short circuit current density of 0.75 mA/cm² and an open circuit voltage of 0.60 V under AM1.5. The photovoltage of the solar cell was greatly enhanced by PCBM:P3HT blend. The capacitance–voltage, the conductance–voltage, the series resistances–voltage characteristics of the solar cell were measured in a wide range of frequency for the first time for DSSC applications. The capacitance–voltage shows a behavior from the positive to negative capacitance due to injection of electrons from the FTO electrode into TiO₂. It is evaluated that the photovoltaic performance of the dye-sensitized solar cell can be improved using various organic semiconductors.     

Synthesis and photovoltaic properties of oligothiophene derivatives

In order to develop novel photovoltaic materials, 5-formyl-2,2′:5′,2″-terthiophene (3T-CHO) and rare earth (terbium) complex based on the 5,5′-bis(5-(2,2′-bithiophene))-2,2′-bipyridine (B2TBPY) ligand, were synthesized. The photovoltaic properties of 3T-CHO and Tb complex based on B2TBPY ligand were studied. Under 78.2 mW/cm² illumination, the ITO/3T-CHO/PCH/Al device has a short circuit current of 1.81 mA/cm², an open circuit voltage of 2.25 V, fill fact of 48.3% and photoelectric conversion efficiency of 2.52%. The ITO/B2TBPY-Tb/PCH/Al device has a short circuit current of 2.47 mA/cm², an open circuit voltage of 0.57 V, fill fact of 29.1% and photoelectric conversion efficiency of 0.52%.     

Plasma_sprayed components for SOFC applications

The major challenge in the development of plasma sprayed components for SOFC was the fabrication of dense electrolytes by atmospheric plasma_spraying (APS) avoiding cracks typically generated during the spraying process. Compared to conventional plasma_sprayed ceramics both the number of micro_cracks and segmentation cracks have to be reduced considerably to achieve sufficiently low leakage rates.Based on a detailed understanding of the formation of plasma_sprayed coatings appropriate process conditions have been established to reach the target values. The major influencing factors are the particle properties in the plasma jet, the substrate temperature, the kind of movement of the gun during deposition, the particle size distribution of the used YSZ powder, and the powder feeding rate. In addition, also the used APS gun plays a major role. With the Triplex II gun it was possible to produce rather thin (≤ 40 μm) YSZ layers with sufficiently low leakage rates without any thermal post_treatment.As substrates tape_casted ferritic steel sheets have been used. The anode was also sprayed by APS using a separate injection of NiO and YSZ. Electrochemical performance was measured after wet_chemically applying a LSCF cathode. The values of the measured open circuit voltage (OCV) were comparable to the ones of sintered cells, indicating the high density of the produced electrolytes. The optimized cells showed at 0.7 V cell voltage a power density of 500 mW/cm² @ 1073 K.     

Copper film deposition rates by a hot refractory anode vacuum arc and magnetically filtered vacuum arc

Two vacuum arc deposition techniques were compared for metal film deposition: 1) filtered vacuum arc deposition (FVAD), which applies a magnetic field to separate the plasma from macroparticles (MPs) generated in the cathode spots, and 2) hot refractory anode vacuum arc (HRAVA) deposition, in which anode plasma plume forms by re-evaporation of cathode material from the hot anode surface and MPs are vaporized in the hot interelectrode plasma. A Cu cathode and an arc current of 200 A were used in both systems.The FVAD film thickness was axially symmetric to within 10-20%. The focused plasma jet in the FVAD system covered a circular area, where the radius for half-thickness is ∼ 30 mm. The deposition rate was constant in time and maximal (about 0.25 μm/min) in the center of the circular area. The mass deposition rate was about 9.5 mg/min assuming bulk density.The HRAVA deposition rate initially increased with time and saturated at a maximum of ∼ 2.3 μm/min after 1 min. The plasma expanded radially, and was deposited on a cylindrical area of 100 cm² and height ∼ 20 mm, which was co-axial with the electrode axis. The thickness distribution was axially symmetric within 10%. The steady-state mass deposition rate was 400 mg/min. The HRAVA system produced an almost MP-free radially expanded mass throughput and cathode utilization efficiency ∼ 40 times greater than with the FVAD system.     

Dip coating technique in fabrication of cone-shaped anode-supported solid oxide fuel cells

A simple and cost-effective dip coating technique was successfully developed to fabricate NiO-YSZ anode substrates for cone-shaped anode-supported solid oxide fuel cells. A single cell, NiO-YSZ/YSZ/LSM-YSZ, was assembled and tested to demonstrate the feasibility of the technique applied. Using humidified hydrogen (75 ml/min) as fuel and ambient air as oxidant, the maximum power density of the cell was 0.78 and 1.0 W/cm² at 800 and 850 °C, respectively. The observed open-circuit voltages (OCV) was closed to the theoretical value and the scanning electron microscope (SEM) results revealed that the microstructures of the anode substrate and the cathode layer are porous and the electrolyte film is dense.     

Electrochemical studies on the performance of SS316L electrode in electrokinetics

Organic and trace metal pollutants are removed by employing various electrodes in an electrokinetic (EK) process. Stainless steel was used either as an anode or a cathode by various investigators in electroremediation systems. In the present study, the role of SS316L as an anode and cathode in EK system was studied by the measurements of pH, conductivity of electrolyte, and potential of the anode and cathode at different current densities. The weight loss of the anode and cathode and the leaching of chromium, iron, and nickel at different current densities were measured and discussed with an electroosmosis process. The electrochemical behavior of SS316L electrode in neutral, acidic and alkaline pH in soil environment was studied by an electrochemical technique viz. polarization study. Surface analysis of SS316L after EK was done by XPS and SEM. The higher conductivity was noticed at anolyte when compared to catholyte. The weight loss of the anode was in the following order 0.615 > 0.307 > 0.123 mA/cm² and the cathode corrosion rate was vice versa. Peroxide production was also noticed at the anolyte, which may encourage the degradation of the total organic content (TOC) in the soil. The OCP (open circuit potential) of SS316L was about +75 mV vs SCE in the soil extract; while adding acetic acid, the potential shifted to the positive side, to about +380 mV vs SCE. The breakdown potential and the range of passivation potential were higher in acetic acid added system when compared to other systems. Pitting was observed on both the anode and cathode within 48 h during the EK process. The present study concludes that SS is not a proper electrode material for the EK process.     

Electrochemical investigations of self-doped polyaniline nanofibers as a new electroactive material for high performance redox supercapacitor

Self-doped polyaniline (SDPA) nanofibers were deposited on platinum (Pt) electrode by reverse pulse voltammetric (RPV) method and their electrochemical performance was evaluated in an aqueous redox supercapacitor constituted as a two electrode cell in a weak acidic medium. Scanning electron micrographs clearly revealed the formation of nanofiber structures with diameters in range of 60–90 nm under optimum experimental conditions. Different electrochemical methods including galvanostatic charge–discharge (CD) experiments, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out in order to investigate the applicability of the system as a redox supercapacitor. Based on the charge–discharge results obtained, the SDPA represented high specific capacitance, specific power and specific energy values of 480 F g⁻¹, 436 W kg⁻¹ and 9.40 Wh kg⁻¹, respectively, at a current density of 5 mA cm⁻². The present study introduces new nanofiber materials for electrochemical redox capacitors with advantages including low cost, long cycle-life and stable at low acidic solutions of pH 3.     

Fabrication of complex shape electrodes by localized electrochemical deposition

Localized electrochemical deposition (LECD) is a promising technology for fabrication of high-aspect ratio electrode of various materials. This technology is found to be one of the simple and inexpensive ways to fabricate electrodes for micro-EDM. This study presents a novel method to manufacture electrodes with complex cross-section using mask of non-conductive material. In this study, the mask is placed between the anode and cathode, which is immersed in mixed electrolyte of copper sulfate, 1.0 M sulfuric acid and as an additive agent 0.04 g/l of thiourea. The deposition of copper is localized on the cathode surface using a mask and applying ultra short voltage pulses between the anode and cathode. In this setup the cathode is placed above the anode and mask, so that the deposited electrode can be used directly for EDM or any application without changing tool orientation. The deposition characteristics such as size, shape, surface, and structural density according to gap between the anode and mask, applied voltage, pulse frequency and duty ratio have been investigated in this study. Finally, appropriate conditions have been found out for effective fabrication of smooth and fine-grained deposited electrodes based on the findings of the various experiments.     

Electrochemical properties of rechargeable organic radical battery with PTMA cathode

The electrochemical properties of the organic radical battery (ORB) having a lithium metal anode and a cathode consisting of a nitroxide radical polymer poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) with 1M LiPF₆ as an electrolyte in ethylene carbonate (EC)/dimethyl carbonate (DMC) have been evaluated at room temperature. The cell, with a thin cathode of 17 μm thickness incorporating 40 wt.% of PTMA, exhibited the full theoretical specific capacity at current densities up to 10 C (∼1 mA/cm²). However, a decrease in the specific capacity and an increase in the ohmic resistance were observed at higher current densities. The cell performance was good even on repeated charge-discharge cycles as an excess of 85 % retention of the initial discharge capacity was observed. This was true even after 400 cycles. However, a gradual decrease in capacity, an increase in charge-discharge voltage separation, and an electrode/electrolyte interfacial resistance have been observed after a large number of cycles. The examination of the scanning electron micrographs of the cathode material revealed that prolonged cycling resulted in the agglomeration of PTMA particles. These in turn increased the resistance and decreased the capacity of the cell.     

Preparation and characterization of tungsten nanopowders from WC scrap in molten salts

Tungsten carbide (WC) scrap was used as a consumable anode to prepare tungsten powder in NaCl–KCl melt at 1023 K for the first time. The electrolysis process was investigated. Results showed that the tungsten component in WC anode was dissolved as W^2 + into the NaCl–KCl melt. The cathode reaction was controlled by the diffusion of tungsten ions. The effect of electrolysis parameters, including the anode–cathode distance, cathode current density and different electrolysis ways (galvanostatic and potentiostatic electrolysis), on the purity and grain size of the cathode deposits was studied. It showed that a large anode–cathode distance was beneficial to the formation of pure tungsten powder at the cathode. With increasing the cathode current density, the tungsten grain size first decreased and then increased. When the cathode current density was 0.125 A cm^− 2, tungsten powder with a diameter of smaller than 100 nm was obtained. Deposits prepared through galvanostatic and potentiostatic electrolysis was compared in the end.     

Charge transport properties of an organic solar cell

The electronic properties of ITO/PEDOT-PSS/P3HT-PCBM/LiF/Al organic solar cell have been investigated using current-voltage and capacitance-voltage techniques. The electrical parameters like ideality factor n, series resistance R_s and barrier height ?_b, have been extracted using current-voltage and capacitance-voltage techniques. The photovoltaic parameters such as open circuit voltage V_oc, short circuit current I_sc and fill factor FF were determined from current-voltage characteristics of the solar cell under illumination. The ideal value than unity for the organic solar cell indicates the presence of non-ideal behaviour. The barrier height of the solar cell is found to be dependent both temperature and applied voltage and the model of Gaussian distribution of the barrier height was presented for explaining their anomalous behaviour. The standard deviation of the barrier height distribution σ_o indicates the presence of interface inhomogeneities. The ideality factor n, open circuit voltage V_oc, short circuit current density J_sc, fill factor FF and Richardson constant A* values for the organic solar cell were found to be 2.29, 0.58 V, 5.84 mA/cm², 0.31 and 10.41 A/cm² K², respectively.     

Ar/O2 gas pressure dependences of a pulsed zirconium arc and extracted ion characteristics

A pulsed dc zirconium arc discharge is generated in an argon diluted oxygen gas by separating a pin electrode as an anode from the cathode. The arc is transiently generated, and its life time is approximately 3 ms for a series resistance of 1 Ω and a dc output of 33 V. The life is prolonged and the plasma becomes stable with increasing the arc current. A target with a diameter of 100 mm is set at 150 mm from the arc source, and is immersed in the plasma. A pulse voltage is applied to the target to extract ions from the plasma. The ion current is not detected after approximately 8 ms since the plasma initiation. When the plasma is generated in oxygen without argon, the plasma generation time is scattered, and the plasma is unstable. An ion density is estimated from the temporal behavior of the target voltage in the recovery region after the pulse voltage. The ion density at the target is approximately 2.5 × 10¹⁵ m^− 3 at a mixed gas pressure of 1.9 Pa, which corresponds to the plasma density of 1.1 × 10¹⁷ m^− 3 under an assumption of electron temperature of 1 eV.     

AOT reverse micelle, a new organized medium for the electrosynthesis of polyaromatic hydrocarbons; application to the electropolymerization of biphenyl

Electrosynthesis of poly(biphenyl) (PBP) films was performed in an AOT [sodium bis(2-ethylhexyl) sulfosuccinate] reverse micelle by cyclic voltammetry and chronopotentiometry on a platinum electrode. An electroactive PBP film was formed either by cyclic voltammetry between −0.6 and 1.65 V/Ag/AgCl or under current control (j = 0.2 mA/cm²). PBP films were characterized electrochemically and spectroscopically (MALDI-TOF mass spectrometry), NMR, Raman, FT-IR, X-ray photoelectron and UV–vis spectroscopy). The structure of the PBP films involved sequences of ramified trimer possessing quinoid forms. This type of sequences can give strongly condensed oligomers with PBP molar mass up to 2669.6 g/mol according to the electrosynthesis charge.     

Mn3O4 doped with nano-NaBiO3: A high capacity cathode material for alkaline secondary batteries

In this paper we report a novel Mn₃O₄ electrode doped with nano-NaBiO₃. It is demonstrated that doping with nano-NaBiO₃ alters the electrochemical inertia of Mn₃O₄, converting it into a rechargeable secondary alkaline cathode material that exhibits highly efficient charge/discharge properties. While a pure Mn₃O₄ electrode can barely maintain a single charge and discharge cycle, the cycling capacity of the Mn₃O₄ electrode doped with nano-NaBiO₃ can reach and become stable at 372 mAh g⁻¹ under 60 mA g⁻¹. The doped cathode can also maintain a cycling capacity of 261 mAh g⁻¹ while holding a 95.3% reversible capacity after 60 cycles at a high rate of 500 mA g⁻¹. Moreover, the experimental results indicate that charging time for an alkaline battery using doped Mn₃O₄ cathode could possibly shorten to as little as 30 min.     

Characterization of planer cathode-supported SOFC prepared by a dual dry pressing method

Cathode-supported solid oxide fuel cells (SOFCs), comprising porous (La_0.75Sr_0.25)_0.95MnO_3−δ (LSM) + Sm_0.2Ce_0.8O_1.9 (SDC) composite cathode substrate and 11 mol%Sc₂O₃-doped ZrO₂ (ScSZ) electrolyte membranes layer, were successfully fabricated via dual dry pressing method. NiO-SDC anode was prepared by slurry coating method. Phase characterizations and microstructures of electrolyte and cathode were studied by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). No interface reaction took place between LSM/SDC cathode substrate and ScSZ electrolyte layer after sintered at 1300 °C. The cell performances were measured at 800 and 750 °C, respectively, by changing the external load. The peak power densities were 0.228 and 0.133 W cm⁻², and the corresponding open-circuit voltages of the cell were 1.092 and 1.027 V at 800 and 750 °C, respectively. Impedance analysis indicated that the performances of the SOFCs were determined essentially by the composition and microstructure of the electrode.