H2SO4 Aqueous Solution Research Articles

Optical and photoelectrochemical properties of nitrogen-doped a-SiC thin films deposited by reactive sputtering method at room temperature

ABSTRACT This paper studies optical properties of Nitrogen-doped a-SiC amorphous, commonly called, silicon carbonitride (SiCN) thin films deposited on polished and textured silicon wafers by reactive RF magnetron sputtering technique. Different samples were made at room temperature by sputtering a silicon carbide (SiC) target in argon and nitrogen mixture environment. The FTIR measurement confirms the presence of Si-C and Si-N bonds. The peaks corresponding to Si-C are 611, 653, 669, 740, 834 cm−1 and the peaks corresponding to Si-N are in the range ~870–950 cm−1. The optical properties were achieved from reflectivity spectra by UV-visible spectroscopy. The refractive index (n < 2.5) and the optical gap (Eg>2.2 eV) of the deposited films depended on the used argon and nitrogen flows. The electrochemical properties of amorphous p-type a-SiC/N thin films on p-Si substrate were investigated as electrodes in H2SO4 aqueous solutions in the dark and under the white light illumination. The SiCN films show a good suitability for the antireflective coating application and can be applied to fabricate high efficient and stable SiCN catalysed n + p-Si photocathode with pyramid surface for PEC CO2 conversion.

Applicability of Waste Engine Oil for the Direct Production of Electricity

New methods for the use of waste products as input for other technologies are a constant subject of research efforts. One such product is waste engine oil. Due to the constantly increasing number of motor vehicles in the world, the recycling or application of engine oils for energy production purposes is currently of considerable importance. This paper contains research regarding the analysis of the electro-oxidation potential of waste engine oil, and thus the possibility of using such oil as a material in fuel cells. The research demonstrates the basic possibility of the electro-oxidation of this oil emulsion on a platinum electrode in an acid electrolyte (aqueous solution of H2SO4). It was shown that in the temperature range of 20–80 °C, the electro-oxidation of the waste engine oil emulsion occurred for all emulsion concentrations (0.005%, 0.010%, 0.030%, and 0.060% of the reactor volume). The maximum current density obtained in the measurements was 21 mA·cm−2 at the temperature of 60 °C (0.030% waste oil and 0.5 M electrolyte). Although this value is small, it encourages further research on the use of used engine oil for the direct generation of electricity.

Design and synthesis of polyaniline/MWCNT composite hydrogel as a binder-free flexible supercapacitor electrode

The novel polyaniline/MWCNT composite hydrogel has been successfully synthesized on carbon cloth using in situ oxidative polymerization of aniline in the presence of MWCNT and phytic acid which can further be used as a binder-free electrode for supercapacitor. The use of electrode without binder is an effective approach to get better electrochemical behavior, which makes the ions move quicker. The supercapacitor cell has been built in a Teflon Swagelok assembly by sandwiching a separator impregnated with 1 M H2SO4 electrolyte between two symmetrical hydrogel electrodes and used further for electrochemical characterization. The electrochemical behavior of supercapacitor electrodes has been explored in a two-electrode cell configuration using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements. The electrochemical results reveal that in 1 M H2SO4 aqueous solution, polyaniline/MWCNT composite hydrogel possesses a high specific capacitance (Cs) value of 277.59 F/g as compared to Cs value of 142.24 F/g for polyaniline hydrogel at 0.25 A/g. The polyaniline/MWCNT electrode shows superior rate capability and outstanding cyclic stability up to 5000 consecutive cycles. The electrochemical performance of composite hydrogel may be attributed to its well-designed nanostructure and the collective effect of both components. It may be concluded that as prepared composite hydrogel serves as a favorable electrode material for highly capable flexible energy storage system.

Вплив складу електроліту на характеристики синтезованого під час твердого анодування алюмінію оксидного шару

The aim of the study. By introducing strong oxidizers to the electrolyte form anode layers on the surface of aluminum with increased mechanical characteristics. To determine the effect of the duration of the formation of an anode layer to change its properties. Hard anodizing was performed at a temperature of –4...0C for 60 min. A 20% aqueous solution of H2SO4 was used as the base electrolyte. During anodizing, the current density was 5 A/dm2. To determine the effect of strong oxidants on the characteristics of the anode layers (oxide), 30 were added to the electrolyte; 50; 70 and 100 г/лof hydrogen peroxide (H2O2). In some cases, it was purged with an ozone-air mixture at a rate of 5 mgmin/l of ozone. It was found that the oxide layer (Al2O3H2O) during hard anodizing on aluminium alloys forms not only oxygen ions, which are formed by the decomposition of water, but also neutral oxygen atoms, which are formed by the decomposition of hydrogen peroxide and ozone. It was found that hydrogen peroxide, as well as blowing the electrolyte with an air-ozone mixture increase the thickness and microhardness of the anodized layer by 50% due to the reduction of the number of water molecules in alumina by half. Hydrogen peroxide and ozone apparently also reduce the thickness of the barrier layer of the coating, through which oxygen and aluminium ions penetrate and which, when combined, form an oxide layer. Conclusions. 1. It has been established that aluminum anodizing for 60 minutes. provides an increase in its properties. Changing the composition of the electrolyte contributes to the growth of microhardness in 1.2 ... 1.7 times. The resistance of abrasive wear increases with the content of different amounts of applications in the electrolyte and the maximum is at 30 g / l H2O2. Blowing the base electrolyte ozone provides an increase in the microhardness of the layer from 380 to 510 HV. The higher loss of mass for higher microhardness is caused by an increase in porosity of coatings. 2. It is determined that an increase in the anodization time in the baseline electrolyte to 120 and 180 minutes contributes to the growth of microhardness to 640 HV compared to an anodized layer for 60 minutes. Loss of mass in the study of abrasive wear is less than 3-4 times with longer anodation than at 60 minutes in the baseline electrolyte.

CO2 activation of bamboo residue after hydrothermal treatment and performance as an EDLC electrode.

CO2 activation of the solid residue of bamboo after hydrothermal treatment, which is used for the production of xylo-oligosaccharide, was investigated in detail. The reference temperature for carbonization and CO2 activation was 800 °C. The activated carbon from a solid residue was demonstrated to have a higher potential for making EDLC electrodes than bamboo activated carbon thanks to its very low ash content (almost 0) and high porosity structure with a BET surface area up to ca. 2150 m2 g−1. The electrochemical performance of ELDC electrodes prepared from solid residue-derived activated carbon in 1 M H2SO4 aqueous solution was measured and well compared with carbon from bamboo. Through investigation, it is clear that the capacitance of the electrode made from the solid residue has a better capacity than that of raw bamboo.

Charge- and Proton-Storage Capability of Naphthoquinone-Substituted Poly(allylamine) as Electrode-Active Material for Polymer–Air Secondary Batteries

1,4-Naphthoquinone (NQ) undergoes a two electron and two proton redox process in one step at a potential of −0.05 V (vs Ag/AgCl) in 0.05 M H2SO4 aqueous solution. Its heterogeneous electron transfe...

Electrocatalytic Hydrogen Evolution Reaction with Multilayer Graphene-Covered Ni Particles Synthesized by Microwave-Assisted Catalytic Methane Decomposition

It is known that the type of electrocatalysts used in the hydrogen evolution reaction (HER) are critical for energy technologies such as water splitting and hydrogen fuel cells. Thus, in recent years, increasing attention has been paid to the development of noble metal-free electrocatalysts. It has recently been reported that Ni–C-based catalysts exhibit HER activity comparable to that of Pt in an acidic medium. Moreover, we have recently developed a new metal–carbon powder, which contained multilayer graphene-covered Ni particles as the main component, synthesized by multimode microwave-assisted catalytic CH4 decomposition using a multimode microwave reactor. Thus, in this study, we investigated the electrocatalytic HER over the Ni–C powder using a digital potentiostat equipped with a potential sweep unit. Figure 1 shows the current–potential curve in the presence or absence of dissolved oxygen in an aqueous H2SO4 solution; the curve was obtained using a carbon paste electrode filled with the Ni–C powder. A reduction current based on HER was observed from approximately 0.0 V (referred vs. SHE), while the onset potential was shown to be slightly affected by the presence or absence of dissolved oxygen. Therefore, the Ni–C powder can be used as a noble metal-free electrocatalyst to implement the HER with excellent electrochemical performance in acidic medium. *Figure 1. Linear sweep voltammograms with the carbon paste electrode (Φ = 3 mm) filled with the Ni–C powder, synthesized by a multimode microwave-assisted process in an acidic solution under different atmospheres. SR = 10 mV/s. Figure 1

(Invited) Electrodeposition of Manganese Oxides Utilizing Hydrothermal Electrochemical Technique

Hydrothermal electrochemistry can conduct electrochemical experiments under high temperature and pressure conditions and is one of the useful methods to fabricate size-controllable and highly crystalline materials. Although this technique has been applied to electrodeposition of metal oxides like BaTiO3 (Yoshimura et al., Jpn. J. Appl. Phys., 28, L2007, 1989), precise control and examination of electrochemical process was hard to be achieved in previous reactors because they adopted two-electrode systems. Moreover, reaction pressure was determined by temperature, so it is difficult to discuss their specific contribution to the electrochemical process.Recently, we have developed hydrothermal electrochemical reactor in which three-electrode system was adopted in order to control and monitor the electrochemical process precisely. This system also achieves independent control of temperature and pressure so that we can discuss their contributions to the final products. Here in this work, we attempted to fabricate Manganese oxide thin film with electrodeposition technique under different temperature and pressure, and examined their electrochemical water oxidation activity. Manganese oxides are prepared in industry with electrodeposition technique, so they are good candidates as model compounds to examine the property of our home-made hydrothermal electrochemical reactor.MnO2 was deposited on Ti substrate with galvanostatic condition of 10 mA /cm2 for 20 min utilizing 0.5 M MnSO4 / 0.2 M H2SO4 aqueous solution as a precursor. Based on XRD analysis, all deposited samples were ε-MnO2. When we increase deposition temperature, XRD peaks got sharpen, indicating the crystallinity increased. SEM observation clarified their morphological difference. Namely, MnO2 deposited at 160℃ possessed needle-like structure, while spherical structure was observed for sample deposited at 100℃. To examine the effect of pressure on deposition products, we conducted electrodeposition under different pressure from 0.1 to 4 MPa while maintaining temperature at 100℃. As a result, XRD peaks were slightly shifted depending on pressure. This means lattice constant is controllable by regulating deposition pressure.Their electrochemical water oxidation activity also demonstrated the advantage of hydrothermal electrodeposition compared with conventional technique. After annealing at 200℃, 160℃-electrodeposited sample exhibited superior activity to 100℃-deposited sample. Although the elucidation of the reason for higher catalytic activity is future work, those results indicate our hydrothermal electrochemical technique is widely applicable to material synthesis such as metal oxides, metal sulfides, and so on. Figure 1

Electrochemical Hydrogenation of Toluene to Methylcyclohexane over Rh-Modified Pt Nanoparticles: Effect of Rh Coverage and Electrochemical Surface Area

Introduction Organic hydrides are known to be hydrogen carriers to achieve large-scale storage/transportation system of hydrogen. Especially, a couple of toluene (TL) and its hydrogenation product, methylcyclohexane (MCH), is promising because they are liquids at ambient temperature and pressure to use existing infrastructure and MCH has high hydrogen storage density (6.1 wt.%). In general, MCH is regenerated by the hydrogenation of TL with molecular hydrogen on appropriate catalysts, and another chemical or electrochemical process is required for the production of molecular hydrogen. However, electrochemical hydrogenation of TL to MCH is one-pot process, in which the electrochemical generation of atomic hydrogen by one-electron reduction of H+ and the hydrogenation of TL with atomic hydrogen consecutively proceed on the same catalyst surface. The standard potential of the electrochemical TL hydrogenation process is more positive than that of hydrogen evolution reaction, indicating the former is more energy-saving.1, 2 Pt nanoparticles loaded on carbon (Pt/C) are active for electrochemical hydrogenation of TL to MCH.1, 2 Recently, it has been found in our group that Rh-modified Pt/C (Rh/Pt/C) catalysts exhibited higher current for electrochemical hydrogenation of TL than Pt/C. In order to evaluate the specific activity and investigate the relationship between electrochemical hydrogenation activity and Rh loading or Rh coverage (θ Rh), it is necessary to separately evaluate the electrochemical surface areas (ECSAs) of Pt and Rh, but it is difficult because the potential region of hydrogen adsorption/desorption for Pt and Rh overlaps. In this study, we have succeeded in separately evaluating the ECSAs of Pt and Rh for Rh/Pt/C catalysts with different quantities of deposited Rh by using the difference in CO stripping potential between Pt and Rh, and estimated the Rh coverage (θ Rh) to discuss the relationship with catalytic activity. Experimental The commercial Pt/C (Tanaka Kikinzoku Kogyo, TEC10E50E) powder was dispersed in ultrapure water. Different concentrations (1.2, 2.4, 3.6 and 4.8 mM) of rhodium chloride aqueous solutions were added into the dispersion, followed by hydrogen bubbling for 1 h at 30 °C. The final black powder is named Rh0.19/Pt/C, Rh0.38/Pt/C, Rh0.56/Pt/C and Rh0.76/Pt/C hereafter. For the preparation of a catalyst electrode, each catalyst ink was cast on a GC substrate (diameter: 5 mm) and dried overnight to make a working electrode. The counter electrode, reference electrode and electrolyte were a platinized Pt electrode, reversible hydrogen electrode (RHE) and 0.5 M H2SO4 aqueous solution, respectively. For the ECSA evaluation, CO was saturated into the electrolyte solution at 0.30 V. After removing dissolved CO by Ar-bubbling, the electrode potential was stepped from 0.30 to 0.75 V, and kept at this potential for 15 s to preferentially desorb CO adsorbed on the Rh surface. After that, cyclic voltammogram was measured between 0.05 and 1.2 V. Results and Discussion The θ Rh increased with the Rh/Pt mole ratio for Rh/Pt/C catalysts, and stagnated as the Rh/Pt mole ratio excessed 0.38 (Fig. 1). However, the fraction of ECSA of Rh (ECSARh) to total ECSA of Pt and Rh (ECSARh/Pt/C) continued to increase with the Rh/Pt mole ratio, suggesting that Rh was preferentially accumulated on deposited Rh as θ Rh reached ca. 0.2. The Tafel slope of the electrochemical hydrogenation of TL on the Rh0.19/Pt/C, Rh0.38/Pt/C, Rh0.56/Pt/C and Rh0.76/Pt/C catalysts was ca. 34, 34, 33 and 32 mV dec-1, respectively. Each Tafel slope was close to that for the Pt/C catalyst, suggesting that electrochemical TL hydrogenation on Rh/Pt/C follows the same reaction mechanism and rate-determining step, which is the addition reaction of adsorbed TL with atomic hydrogen. The change in hydrogenation current per ECSAPt (j Pt) at 0 V vs. RHE with the Rh/Pt mole ratio showed the similar tendency to that in θ Rh (Fig. 1), suggesting that the electrochemical hydrogenation of TL preferentially occurs at the interface between Pt and Rh.Galvanostatic electrolysis of 30 vol.% TL with the Pt/C and Rh/Pt/C catalysts at −200 mA cm−2 was carried out with polymer electrolyte membrane electrolysis cell. It was found by GC/MASS analysis that sole reaction product in the electrochemical hydrogenation of TL was MCH. The faradaic efficiency for MCH production and conversion of TL to MCH were also increased with the increase of θ Rh, and the side reaction, hydrogen generation, was suppressed. These results clearly indicate that the Rh/Pt/C catalysts are superior to Pt/C. References 1 Y. Bao, T. W. Nappom, K. Nagasawa, S. Mitsushima, Electrocatalysis, 10, 184 (2019).2 S. Mitsushima, Y. Takakuwa, K. Nagasawa, Y. Sawaguchi, Y. Kohno, K. Matsuzawa, Z. Awaludin, A. Kato, Y. Nishiko, Electrocatalysis, 7, 127 (2016). Figure 1

Oxygen Reduction Reaction Activity of Iron (II) Phthalocyanine Monolayers in Acidic Media Studied Using a Rotating Disk Electrode Technique

Metal complexes such as metalloporphyrins and metallophthalocyanines are widely studied in various research fields due to their unique physical and chemical properties. Especially, their catalytic activities for oxygen reduction reaction (ORR) are of great interest because this reaction plays an important role in energy conversion or biological redox processes. Among various metal complexes, Iron (II) phthalocyanine (FePc) is expected as a candidate for four-electron ORR catalysts. However, most of the kinetic studies for ORR have been carried out using heat-treated catalysts of FePc. Unfortunately, their chemical structures become ill-defined after the heat treatment, and thus, the nature of active sites is still unclear. Actually, there is a possibility that four-electron ORR activity is induced by dimeric FePc. The intrinsic activity of monomeric FePc, especially in acidic media, is still under discussion. In this study, well-defined monolayers of monomeric FePc complexes were fabricated on chemically modified Au surfaces using two-step assembly [1]. Their ORR activity was quantitatively measured in acidic media using a rotating disk electrode (RDE) technique. The catalytic behavior of FePc was compared with that of Cobalt (II) tetraphenylporphyrins (CoTPP), which is known as two-electron ORR catalyst.The monolayers of FePc or CoTPP were fabricated on Au surfaces as follows. First, an Au disk electrode with diameter of 10 mm was modified with self-assembled monolayers of pyridine-4-thiol (PySH) or 1,6-diisocyanohexane (C6DI). Next, metal complexes of FePc or CoTPP were immobilized on top of these molecular monolayers through axial ligation with their different terminal groups. The ORR activity of these samples was measured in O2-saturated 0.05 M H2SO4 aqueous solution using the RDE method.Figure shows rotation rate dependences of RDE polarization curves for CoTPP and FePc on C6DI-modified Au. According to the Koutecky-Levich analysis of these curves at 0 V vs. RHE, the electron transfer number was estimated to be 1.9 for CoTPP, indicating that CoTPP indeed catalyzed only two-electron ORR. On the other hand, the estimated transfer number for FePc was 2.4, suggesting that this complex was indeed able to catalyze the four-electron ORR in the acidic condition. Interestingly, the catalytic behavior of FePc on C6DI-modified Au was apparently different from that on PySH-modified Au. In the poster, we will present details about the ORR activities of FePc measured on various monolayer-modified Au electrodes.Reference[1] Toyama T, Sato S, Motobayashi K, Uosaki K, Ikeda K. J Solid State Electrochem. DOI: 10.1007/s10008-019-04461-9.Figure. Rotation rate dependence of RDE polarization curves for FePc/C6DI/Au and CoTPP/C6DI/Au measured in 0.05 M H2SO4 solution, where FePc/C6DI/Au and CoTPP/C6DI/Au denote FePc and CoTPP monolayers immobilized on C6DI-modified Au, respectively. Figure 1

Yield of the Fricke dosimeter irradiated with the recoil α and Li ions of the 10B(n,α)7Li nuclear reaction: effects of multiple ionization and temperature

Monte Carlo track chemistry simulations were used to investigate the effects of multiple ionization (MI) of water on the yields (G values) of the ferrous sulfate (Fricke) dosimeter, which was irradiated with low-energy α and lithium ion recoils from the 10B(n,α)7Li nuclear reaction as a function of temperature from 25 to 350 °C. Calculations were performed individually for 1.47 MeV α-particles and 0.84 MeV lithium nuclei with dose-average linear energy transfer (LET) values of ∼196 and 225 keV/µm at 25 °C, respectively. The total yields were obtained by summing the G values for each recoil α and Li ion weighted with its fraction of the total energy absorbed. At room temperature, our G(Fe3+) values calculated under aerated and deaerated conditions only agreed well with the experimental results, provided the MI of water was incorporated in the simulations. This strongly supports the importance of the role of MI of water in the high-LET radiolysis of water. We also simulated the effects of MI of water on G-values for the primary species of the radiolysis of deaerated 0.4 M H2SO4 aqueous solutions by 10B(n,α)7Li recoils. As with the Fricke dosimeter, the best agreement between experiment and simulation was found at 25 °C when the MI of water was included in the simulations. It was also shown that G(Fe3+) decreases slightly as a function of temperature over the range of 25–350 °C. However, at elevated temperatures, no experimental data were available with which to compare our results.

Rechargeable Aqueous Lithium Batteries with a Hydro- Quinone Sulfonic Acid Potassium Salt and Benzoquinone Sulfonic Acid Potassium Salt Redox Couple

The electrical vehicles (EVs) are considered to reduce CO2 emissions and the consumption of fossil fuels, because the total energy conversion efficiency of batteries is higher than that of internal conversion (IC) engines (1). However, the driving range of the commercialized EVs with the current lithium-ion batteries is considerably lower than that of the vehicles with the IC engines, because the energy density for the lithium-ion battery is low compared with those of the IC engine.In this report, a new type high specific energy density battery is proposed. The proposed battery consists of a water- soluble organic redox couple of hydroquinonesulfonic acid potassium salt (HQSK) and benzoquinonsulfonic acid potassium salt (BQSK) and lithium metal anode. The water soluble redox couple was used for aqueous redox flow batteries (2). The catholyte and lithium metal anode were separated by a water-stable lithium-ion conducting solid electrolyte of Li1.4Al0.4Ge0.2Ti1.4(PO4)3 (LAGTP). The cell reaction is described as shown below in Figure A.The calculated specific energy density of the couple is 740 Wh/kg if lithium metal is used as the anode, which is around two times higher than that of a conventional lithium-ion battery.Figure 1 shows a schematic diagram of the proposed cell, where an equivolume of teragalyme (G4) dissolving (Li(FSO2)2N (LiFSI) in 2:1 molar ratio and 1,3 dioxolane (DOL) (2) was used as an electrolyte between lithium and LAGTP, because LAGTP is unstable in contact with lithium. The LAGTP films were prepared by a tape-casting method (3). LAGTP powder prepared by the sol-gel method was dispersed in a solution of ethanol and toluene, a binder and a plasticizer. The slurry was tape-casted and sintered at 900 oC for 7 h. LAGTP-epoxy resin composite film was prepared by soaking in a mixed solution of 1 M 1,3-phenylenediamine and 2 M 2,2-bis (4-glycidyloxy-phenyl) propane in tetrahydrofuran. It was heated at 170 oC for 24 h.Kinetics of the HQSK/BQSK redox reaction on the Ketjen black (KB) electrode in three type aqueous solutions of 1M H2SO4 (pH 0.2), 5.5 M CH3COOH (AcOH) (pH 1.9), and 1M AcOH-1M CH3COOLi (AcOLi) (pH 4.5) were examined using a beaker-type cell with a Ag/AgCl reference electrode.Figure 2 shows over-potential (η) vs current density (j) curves at 25 ℃ for the HQSK/BQSK redox reaction in different solutions, where the discharging over-potentials (BQSK + 2H+ +2e-→ HQSK) were measured after charged about 20 % of HQSK (HQSK → BQSK +2H+ + 2e-). The charging over-potentials were low and showed no significant dependence on the electrolytes. On the other hand, the discharge over-potentials are dependent on the electrolytes. The lowest discharge one was observed in 5.5 M AcOH aqueous solution.A Swagelok-type full cell of Li / (LiFSI-2G4)-50 vol% DOL / LAGTP / HQSK-BQSK in 5.5 M AcOH / KB showed open circuit voltage of 3.6 V at 25 ℃, which is comparable to the calculated value. The cell was charged successfully at 0.5 mA cm-2 for 30 h, but in the discharge at 0.5 mA cm-2 the voltages were decreased significantly with time. Steady discharge voltages were observed at a lower current density. This result suggests that a catalyst for BQSK reduction should be developed to obtain a high power density battery.References Ginshkumar et al. J. Phys. Chem. Lett. 1, 2193 (2010)Yang et al. J. Electrochem. Soc. 161, A1371 (2014)Morita et al. ACS Omega, 3, 5558 (2018) Figure 1

Electrochemical Properties and Cell Performance of Pd Core-Pt Shell Structured Catalyst Synthesized By Direct Displacement Reaction Method

1. Introduction Carbon supported Pd core-Pt shell structured catalyst (Pt/Pd/C) was synthesized by a simple direct displacement reaction (DDR) method in which Pd core was spontaneously displaced with a Pt precursor upon stirring in N2 saturated H2SO4 aqueous solution at 70°C [1]. Compared with our previous modified Cu-UPD/Pt displacement method [2], DDR method is a simple and suitable synthetic method for mass production of the catalyst. In DDR method, Pt shell was more uniformly formed and the Pt shell coverage was increased. In this study, oxygen reduction reaction (ORR) activity and durability of the catalyst were examined and single cell performance was evaluated. 2. Experimental Pt/Pd/C catalyst was synthesized by DDR method [1]. 600 mg of Pd/C core (particle size: 5.0 nm, metal loading: 46 wt.%, ISHIFUKU Metal Industry) was dispersed in 800 mL of water and pH was adjusted to 1 by 4 M H2SO4 at 5°C under N2 gas atmosphere. K2PtCl4 corresponding to Pt monolayer shell was added and stirred at 5°C for 0.5 h, followed by stirring at 70°C for 3 h. ORR activity of the catalyst was evaluated by RDE technique performed in O2 saturated 0.1 M HClO4 at 25°C with a positive scan rate of 10 mV/s at 1,600 rpm. Pt/Pd/C catalyst was activated by a high activation protocol HAP performed in Ar saturated 0.1 M HClO4 at 80°C [3]. Durability of the catalyst was evaluated by an accelerated durability test ADT (rectangular potential cycling of 0.6 V (3 s)-1.0 V (3 s) vs. RHE performed in Ar saturated 0.1 M HClO4 at 80°C for 10,000 cycles). A membrane electrode assembly (MEA) with active area of 1 cm2 was fabricated by using 25.4 µm thick NafionTM NR211. Pt loading in Pt/Pd/C cathode was 0.11 mg/cm2. I-V performance of the MEA was evaluated at 80°C with H2-Air feeding of 418 and 988 NmL/min., respectively. 3. Results and Discussion Nonuniform Pt shell formation observed in Pt/Pd/C catalyst synthesized by modified Cu-UPD/Pt displacement method was suppressed in Pt/Pd/C catalyst synthesized by DDR method as demonstrated in Fig. 1. CVs of Pd/C core and Pt/Pd/C catalysts are summarized in Fig. 2. Large hydrogen desorption wave observed on Pd/C core in a potential range of 0.05-0.1 V, which is a character of Pd, was decreased in Pt/Pd/C catalyst synthesized by Cu-UPD method, and the wave was further reduced in Pt/Pd/C catalyst synthesized by DDR method, indicating that Pt shell coverage was increased by DDR method. Since potential difference between Pd and Pt2+ in DDR method could be decreased compared with the difference between Cu and Pt2+ in Cu-UPD method, Pt shell was more slowly and uniformly formed and the coverage was increased in DDR method. Furthermore, number of fine catalyst particles decreased and mean diameter increased in the catalyst synthesized by DDR method, suggesting that fine Pd core particles were preferentially dissolved and re-deposited by Cl- anions released from Pt precursor of K2PtCl4.Change in ORR mass activity of Pt/Pd/C catalysts with HAP and ADT is summarized in Fig. 3. Initial ORR mass activity of Pt/Pd/C catalyst synthesized by DDR method exhibited 1,419 A/g-Pt, which was 3.3 times higher than that of Pt/Pd/C catalyst synthesized by Cu-UPD method. The activity was enhanced to 1,688 A/g-Pt by HAP, corresponding to 5.3-fold of a reference Pt/C catalyst (320 A/g-Pt, TEC10E50E, TKK). After ADT, ORR mass activity of the catalyst decreased to 917 A/g-Pt. Thus, the catalyst exhibited higher durability than the catalyst synthesized by Cu-UPD method (after ADT: 389 A/g-Pt). I-V performance of Pt/Pd/C catalyst synthesized by DDR method overcame the performance of a reference Pt/C catalyst (TEC10E50E, Pt loading: 0.10 mg/cm2, TKK) as demonstrated in Fig. 4. The Pt/Pd/C catalyst exhibited current density of 0.061 mA/cm2 at cell voltage of 0.85 V (IR free), which was 3.7-fold of the Pt/C catalyst. We think that Pt/Pd/C catalyst synthesized by DDR method is a promising candidate for achieving highly active and durable catalyst for ORR. Acknowledgement We thank to Mrs. Daimaru and Mikami for MEA evaluation. This study was supported by NEDO, Japan.

Fumed SiO2-H2SO4-PVA Gel Electrolyte CO Electrochemical Gas Sensor

The conventional CO electrochemical gas sensor uses aqueous H2SO4 solution as electrolyte, with inevitable problems, such as the drying and leakage of electrolyte. Thus, research on new alternative electrolytes is an attractive field in electrochemical gas sensors. In this paper, the application of a new fumed SiO2 gel electrolyte was studied in electrochemical gas sensors. The effects of fumed SiO2 and H2SO4 contents on the performance of the CO gas sensor were investigated. The results showed that the optimized composition of the SiO2 gel electrolyte was 4.8% SiO2, 38% H2SO4, and 0.005% polyvinyl alcohol (PVA). Compared with aqueous H2SO4, the gel electrolyte had better water retention ability. The signal current of the sensor was proportional to the CO concentration. The sensitivity to CO was 78.6 nA/ppm, and the response and recovery times were 31 and 38 s, respectively. The detection limit was 2 ppm. The linear range was from 2 to 500 ppm. The gel electrolyte CO sensor possesses equivalent performance to that with aqueous electrolyte.

Urchin‐like CoP nanomaterial as an electrocatalyst for efficient hydrogen evolution reaction

The morphology and structure of the electrocatalysts are important factors affecting their performance for electrochemical splitting water into hydrogen. Herein, the urchin-like CoP nanomaterials with the large specific surface area (SSA) were fabricated through the solvothermal process and the solid-gas reaction for hydrogen evolution reaction (HER). The resulting CoP nanomaterial with a diameter of approximately 4 μm was assembled by the nanowires with a length of about 10 nm. The excellent performance is accessible for HER with a small overpotential of 130 mV and a low Tafel slope of 52 mV/decade in a 0.5 M H2SO4 aqueous solution. Especially, the resulting urchin-like CoP nanomaterials with a large SSA and electric double-layer capacitance lower the electrochemical impedance and accelerate the electron transfer, endowing the excellent performance for HER process.

Uranium extraction from different acidic media using a novel solvent-impregnated resin

In present study, uranium (VI) extraction from different acidic media (e.g. H2SO4, HCl and HNO3 aqueous solutions) using tri-n-octylamine (TOA) impregnated into Siplite LX-16 polymeric resin has been investigated using batch experiments. The extraction parameters including aqueous pH, free acidity, salting-out agent addition, initial uranium concentration, volume of aqueous solution to weight of the impregnated resin (v/w) ratio and the phases contact time have been studied. Batch adsorption studies reveal that the prepared TOA/Siplite LX-16 has a significant capacity for the adsorption of U(VI) from aqueous solutions. The maximum sorption capacity of U(VI) from sulfate solution onto the working resin was 92.74 mg/g at an optimum pH range from 1.4 to 1.6. Quantitative desorption of the extracted uranium has successfully been achieved using 0.75 M NaCl acidified with 0.15 M HCl solution. Finally, a complete precipitation of uranium from the eluate solution was attained by hydrogen peroxide precipitation at pH 2.

High Durability and Electrocatalytic Activity Toward Hydrogen Evolution Reaction with Ultralow Rhodium Loading on Titania

Herein, we report the synthesis of titania supported Rh(0) nanoparticles (Rh0/TiO2) as electrocatalyst for hydrogen evolution reaction (HER) in acidic medium. Rhodium nanoparticles with an average particle size of 2.54 nm are found to be well-dispersed on TiO2 surface. Rh0/TiO2 with very low loading density (3.79 μg cm−2) was attached on the glassy carbon electrode (GCE) by drop-casting method. Electrocatalytic performance of modified GCE was investigated via linear sweep voltammetry (LSV) in 0.5 M aqueous H2SO4 solution after 2000 cycle treatment (Rh0/TiO2-2000) and it was found that Rh0/TiO2-2000 on GCE exhibits superior electrocatalytic activity (TOF: 11.45 s−1 at η = 100 mV, η0:−28 mV, η10 mA cm−2: −37 mV, j0: 0.686 mA cm−2 and Tafel slope: 32 Mv dec−1). More importantly, it provides outstanding long-term stability (10000 cycles) at room temperature for HER, which makes Rh0/TiO2-2000 a promising electrocatalyst for hydrogen generation.

TMeQ[6]-based supramolecular frameworks assembled through outer surface interactions and their potential applications

Cucurbit[n]uril(Q[n])-based supramolecular frameworks assembled through outer surface interactions are characterized by their simple composition, convenient preparation, high yields and controllable structures. The most prominent characteristic of these frameworks is their diversity, with various synthesis methods, structural characteristics, structure directing agents and basic building blocks of Q[n]s. In this work, a symmetric tetramethyl-substituted Q[6] (TMeQ[6]) is selected as the basic building block, with three different TMeQ[6]-based supramolecular frameworks obtained from 1-, 3- and 5 mol/L aqueous H2SO4 solutions, respectively. The outer surface interactions between TMeQ[6] and the adjacent SO42− anions or TMeQ[6] units are the main driving forces for the formation of these frameworks, which exhibit adsorption properties for fluorophore dyes and organic isomers. These adsorption characteristics may lead to the application of these frameworks in the synthesis of solid fluorescent sensors for volatile organic compounds and the adsorptive separation of alkane isomers.

Chemically stable anion exchange membranes based on C2-Protected imidazolium cations for vanadium flow battery

Imidazolium-based anion exchange membranes (AEMs) are attractive as the separator for vanadium redox flow battery (VFB) application. However, the lack of fundamental understanding of the correlations between imidazolium chemical structure and their physical properties as well as cell performance constraints the design of advanced AEMs in VFBs. In this work, by designing the “clickable” imidazolium compounds from C2-methyl or C2-phenyl substituted imidazolium to C2-phenyl substituted benzimidazolium, a series of PSf-based AEMs having pendant C2-protected imidazolium derivatives were prepared by efficient CuAAC reaction to explore how the nature of C2 substitution affected the electrochemical property of AEMs and the resulting VFB performance. Interestingly, PSf-MIm with C2-methyl protected imidazolium group showed lowest area resistance (0.3 Ω cm2, IEC = 1.66 meq./g) in 3 M H2SO4 aqueous solution but unfavorable vanadium permeability due to its highest swelling ratio. The introduction of bulky C2-phenyl substituted benzimidazolium led to the distinct microphase separation in PSf-PhBIm membrane, and thus reduced water uptake, high vanadium selectivity, and comparable conductivity were observed. As a result, the single VFB with PSf-MIm-1.2 membrane exhibited better electrochemical performance with a coulombic efficiency (CE) of 97.0%, and an energy efficiency (EE) of 82.4% at a current density of 120 mA/cm2, higher than those of Nafion N115 membrane (EE = 75.5%) and unsubstituted imidazolium-based AEMs (EE = 80.6%). More importantly, both ex situ stability testing in 1.5 M (VO2)2SO4/3 M H2SO4 solution for 90 days and in situ cycling performance at a current density of 120 mA/cm2 demonstrated that the chemical structure of C2-substituted imidazolium based AEMs remained intact after stability tests as confirmed by NMR analysis, while significant degradation was found for unsubstituted PSf-Im membrane via possible nucleophilic addition mechanism. Therefore, the VFB with PSf-MIm membrane showed the best long-term durability with only 34.1% loss in EE for 3638 h of operating (4800 cycles). This work not only fills the knowledge gap on the structure-property relationship of imidazolium-based AEMs for VFB application, but also gives us new directions to design stable AEMs for durable VFBs.

Comparative study of corrosion resistance between four non-commercial high manganese steel models and 9% nickel steel in aqueous solution of H2SO4

Abstract The present study aims to establish a comparison of corrosion resistance between four (non-commercial) high manganese steel models in relation to 9% nickel steel in an aqueous solution of H2SO4. High manganese steels have emerged as an alternative material for the manufacture of equipment for the storage and transportation of liquefied petroleum gas due to their mechanical properties and mainly for the lower cost compared to 9% nickel steel. The electrochemical techniques used were open circuit potential, linear polarization and electrochemical impedance spectroscopy. The results obtained by these techniques have helped to understand the phenomena that produce a lower corrosion resistance of high manganese steels when compared to 9% nickel steel in aqueous solutions.