mA Cm-2 Of Current Density Research Articles

Co-sensitization of Copper Indium Gallium Disulfide and Indium Sulfide on Zinc Oxide Nanostructures: Effect of Morphology in Electrochemical Carbon Dioxide Reduction.

Recent advances in nanoparticle materials can facilitate the electro-reduction of carbon dioxide (CO2) to form valuable products with high selectivity. Copper (Cu)-based electrodes are promising candidates to drive efficient and selective CO2 reduction. However, the application of Cu-based chalcopyrite semiconductors in the electrocatalytic reduction of CO2 is still limited. This study demonstrated that novel zinc oxide (ZnO)/copper indium gallium sulfide (CIGS)/indium sulfide (InS) heterojunction electrodes could be used in effective CO2 reduction for formic acid production. It has been determined that Faradaic efficiencies for formic acid production using ZnO nanowire (NW) and nanoflower (NF) structures vary due to structural and morphological differences. A ZnO NW/CIGS/InS heterojunction electrode resulted in the highest efficiency of 77.2% and 0.35 mA cm-2 of current density at a -0.24 V (vs. reversible hydrogen electrode) bias potential. Adding a ZTO intermediate layer by the spray pyrolysis method decreased the yield of formic acid and increased the yield of H2. Our work offers a new heterojunction electrode for efficient formic acid production via cost-effective and scalable CO2 reduction.

Fabrication of PANI supported magnesium/cobalt spinel ternary oxide as an efficient oxygen evolution reaction and removal of organic pollutant

The advancement of potent, highly efficient and reasonably priced catalysts is necessary for the production of hydrogen from a renewable source and removal of organic contaminants from waste water. In this study, we demonstrated the dynamic proportion capability of the hydrothermally condensed polymorphic electrocatalyst MgCo2O4/PANI nanocomposite. The composite material has higher surface area of 264 m2 g-1 and electrochemical active surface area of 299.5 cm2. The MgCo2O4/PANI nanocomposite exhibits 201 mV of lower overpotential to attain at 10 mA cm-2 of current density and 66 mV dec-1 of reduced Tafel value. The long-term viability for 50 h is demonstrated using MgCo2O4/PANI at 10 mA cm-2 for O2 production. The findings of this study demonstrated that MgCo2O4/PANI nanocomposite is an affordable, non-precious material, which can be utilized to generate H2 on a large scale. On the other hand, the resultant material was then applied for the Congo Red (CR) dye photodegradation irradiated with visible light with degradation efficiency of 98%. The comparison of nanostructured MgCo2O4/PANI demonstrates that the electrochemical performance for water oxidation processes as well as degradation process is significantly higher than the pure form. The exceptional catalytic performance of MgCo2O4/PANI nanocomposite is due to the large quantity of active sites, some immense oxygen vacancies, and a fast electron transfer rate, with a steady oxygen generating stability of 1500 cycles confirm the endurance of MgCo2O4/PANI nanoarrays, which is beneficial for future industrial application.

Hierarchical cobalt-nitrogen-doped carbon composite as efficiently bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

Developing cost-effective bifunctional oxygen electrocatalysts with superior catalytic performance is essential for the large-scale application of rechargeable Zn-air batteries. Herein, a cobalt-nitrogen-doped carbon catalyst Co-UA-OCB with heavy nitrogen content has been synthesized. The N-doped graphene sheets from carbonized uric acid wrapped on the particles of carbon black to construct a hierarchical microstructure. Benefiting from the higher electrochemical active surface area and well dispersed cobalt particles, the catalyst exhibits a remarkable bifunctional activity toward oxygen reduction (ORR) and evolution reactions (OER) with 0.834 V of half-wave potential for ORR and 1.621 V of OER potential at 10 mA cm2. The rechargeable Zn-air battery fabricated with Co-UA-OCB as the air electrode, delivers 142 mW cm−2 of maximum power density, 799 mAh g−1 of specific capacity, 1000 mWh g−1 of energy density and 1.24–1.29 V of running voltage at 10 mA cm2 of current density. The battery exhibits excellent durability and rechargeability, indicating the Co-UA-OCB is a promising candidate to replace the precious metal-based electrocatalyst for rechargeable Zn-air batteries.

Controlled Synthesis of Cr-Co0.85 Se Nanoarrays for Water Splitting at an Ultralow Cell Voltage of 1.43 V.

Water splitting has attracted more and more attention as a promising strategy for the production of clean hydrogen fuel. In this work, a new synthesis strategy was proposed, and Co0.85 Se was synthesized on nickel foam as the main matrix. The doping of appropriate Cr amount into the target of Co0.85 Se and the Cr-Co0.85 Se resulted in an excellent electrochemical performance. The doping of Cr introduces Cr3+ ions which substitute Co2+ and Co3+ ions in Co0.85 Se, so that the lattice parameters of the main matrix were changed. It is worth noting that the Cr0.15-Co0.85 Se/NF material exhibits an excellent performance in the oxygen evolution reaction (OER) test. When the current density reaches 50 mA cm-2 for OER, the overpotential is only 240 mV. For the hydrogen evolution reaction (HER) tests, the overpotential is only 117 mV to drive 10 mA cm-2 of current density. Moreover, when the Cr0.15-Co0.85 Se/NF material is used as a two-electrode device for whole water splitting, the required cell voltage is only 1.43 V to reach a current density of 10 mA cm-2 , which is among the lowest values of the published catalysts up to now. In addition, the Cr0.15-Co0.85 Se/NF catalyst also exhibits excellent stability during a long period of water splitting. The experimental result demonstrates that the change of the lattice structure has an obvious influence on the electrocatalytic activity of the material. When an external electric field is applied, it facilitates the rapid electron transfer rate and enhances the electrocatalytic performance and stability of the material.

INVESTIGATION OF ELECTROCHEMICAL COLOR REMOVAL FROM ORGANIZED INDUSTRIAL DISTRICT (OID) WASTEWATER TREATMENT PLANTS USING NEW GENERATION Sn/Sb/Ni-Ti ANODES

<p>In this study, the application of Sn/Sb/Ni-Ti electrodes for the treatment of waste streams were investigated which is promising for ozone production by electrolysis of water because of their stability and high potential for ozone evolution reaction. These series of anodes have a high electrochemical ozone generation potential at ambient conditions (approximately up to 40% current efficiency). But using and testing of these novel anodes for real wastewater are too limited in the literature. Titanium mesh substrate coated with Sn/Sb/Ni-Ti alloy was used as anode immersed in wastewater at room temperature with platinized titanium cathode. These electrodes used for COD and color removal from OID wastewater in Inegol, Bursa, Turkey. Five operational parameters were evaluated for electrochemical COD and color removal processes, such as pH, salt content, applied voltage/current, current efficiency and contact time. Experimental results showed that after 30 min the electrochemical oxidation efficiency of COD and color could reach up to 98% and 99% respectively at pH 8.2 and temperature of 25°C as the optimum conditions. Current density observed as the most effective parameter for COD and color removal efficiencies. The lowest energy consumption was between 10-25 mA cm-2 of current density with only 0.6 kWh gCOD−1, while the highest energy consumption was 100 mA cm-2 of current density with 9.12 kWh gCOD−1 . The optimum current density value has been found as 50 mA cm-2 with 4.05 kWh gCOD−1 . These results were also supported with ANOVA test.</p>

The Enhancement Effect of Borate Doping on the Oxygen Evolution Activity of α-Nickel Hydroxide

ABSTRACT: The availability of low-cost, high-efficiency oxygen evolution catalysts is pivotal to the application of renewable energy conversion and storage systems based on solar energy and water splitting reactions. We demonstrate here that a moderate amount (~12 wt%) of borate doping of crystalline α-Ni(OH)2, a common low-cost catalyst, can lower the Tafel slope of the oxygen evolution reaction (OER) from the typical value of 60 mV decade-1 to 43 mV decade-1; and the overpotential for 10 mA cm-2 of current density from 390 mV to 340 mV in 0.1 M KOH aqueous solution. Borate doping also improves the stability of α-Ni(OH)2 in OER. The borate-doped α-Ni(OH)2 can even surpass the reference Ir/C precious metal catalyst in both activity and stability. These results here highlights the potential of borate doping as a promising strategy to increase the catalytic activity of base metal in water oxidation catalysts. Figure Caption: a). Cyclic voltammograms of OER on borate-doped α-Ni(OH)2 (denoted as B-NOH), α-Ni(OH)2 (denoted as NOH), and Ir/C b). The volcano curve of OER overpotential as a function of the boron content of B-NOH c). The proposed mechanism on a borate-coordinated Ni active center. Figure 1

Tungsten-Assisted Phase Tuning of Molybdenum Carbide for Efficient Electrocatalytic Hydrogen Evolution.

Phase tuning during crystal phase transformation is an important but challenging step toward the development of effective hydrogen evolution reaction (HER) catalysts. Herein, we report on a feasible approach to achieve effective polycrystalline molybdenum carbides during transformation from α-phase to β-phase through the regulation of additive (tungsten) amount. Benefiting from the optimal Mo-C bond lengths and abundant active sites, molybdenum carbide prepared with a moderate addition of tungsten enhanced electrocatalytic activity and stability compared with pure α-phase and β-phase Mo2C in the HER, and only required an overpotential of 148 and 93 mV to drive 20 mA cm-2 of current density in 0.5 M H2SO4 and 1.0 M KOH, respectively.

Improvement of Current Efficiency for a Hydrogenation Electrolyzer with Low Concentration of Toluene

IntroductionUsage of renewable energy has been got a lot of attention to find a way to sustainable society against environment and energy issues. To supply of renewable energy on demand, large-scale of energy storage and transportation is needed. Hydrogen is expected to apply for the energy storage and transportation. We have been paid attention the organic hydride, especially toluene (TL)-methylcyclohexane (MCH) system as a carrier for energy storage and transportation, because it is higher energy density than hydrogen with easy to handle, and can use the petroleum infrastructure in existence. Direct electrohydrogenation of TL applied polymer electrolyte fuel cell and industrial electrolysis technologies is a simple process with high energy conversion efficiency [1-3]. In this process, hydrogen is a byproduct to decrease current efficiency of chemical hydrogen. Therefore, the suppression of hydrogen evolution is needed. In this study, we have investigated the effect of catalyst-loaded backing of electrocatalyst layer on the polarization and the current efficiency with low concentration TL feed to improve cell performance. Experimental Mixture of ethanol, H2PtCl6・6H2O and H2O ( the ratio is 3.0 : 0.3 : 1.0 ) were used as a precursor of Pt catalyst on a carbon paper (35BC, SGL Carbon). The paper was dipped in the mixture, and dried at 60oC for 10 min. Then it was heated at 240oC for 6 h in nitrogen atmosphere to prepare Pt loaded cathode backing (called CPt). The carbon paper backing with no Pt is called Cnon-Pt. An anode was the DSE® (De Nora Permelec Ltd.) electrode for oxygen evolution. A cathode was 0.5 mg cm-2 of PtRu/C (TKK) coated on a CPt or Cnon-Pt, and it was hot-pressed(120oC, 0.27 MPa) on a Nafion® 117(DuPont). The anode side of the membrane was made hydrophilic before the hot-pressing. Geometrical electrode area was 11.3 cm-2. 10 ml min-1 of 1 M (=mol dm-3) sulfuric acid, and 5 ml min-1 of 10 mol% TL / MCH were circulated to the anode and the cathode compartments, respectively. 10 mol% concentration of TL feed simulates at the vicinity of outlet in a practical electrolyzer. A Luggin capillary for a RHE was placed near the anode. Polarization was evaluated with constant cell voltage measurement for 5 min at 1.3-5.0 V and 60oC. During the constant cell voltage measurement, the volume of generated hydrogen was determined to evaluate the current efficiency. Resistance of electrolyte evaluated from high frequency intercept in AC impedance at 10-1~105Hz. Results and discussion Figure 1 shows the IR corrected polarization curves with 10 mol% TL feed with CPt (circular) that was loaded about 0.8 mg cm-2 of Pt and Cnon-Pt (triangle, diamond). Upper and lower vertical axes are anode and cathode potentials, respectively. Dashed dotted line shows the theoretical potential of 1.23 V and 0.15 V vs. RHE for anode and cathode reaction, respectively. The polarization curves of the anode with the CPt and Cnon-Pt were almost the same, while the potential of Cnon-Pt cathodes were lower than that of CPt cathode above 300 mA cm-2of current density region. The former showed diffusion limitation, while the latter did not show. Figure 2 shows the current efficiency (WTL →MCH) with 10 mol% concentration of TL feed at 60OC. Side bar shows the fluctuation of current density during constant cell voltage operation. At the low current density below 300 mA cm-2, the WTL →MCH of the CPt was significantly higher than that of the Cnon-Pt. The WTL →MCH of Cnon-Pt rapidly decreased when the current reached to 400 mA cm-2, which related to the large change of the cathode potential as shown in Figure 1. In all the current regions, the fluctuation of the CPt was significantly smaller than that of the Cnon-Pt. Therefore, the CPtwould promote the catalytic hydrogenation of TL with hydrogen bubble generated as side reaction in cathode. The decrease of hydrogen gas in the backing would lead to improve the TL mass transfer. Acknowledgments This work was supported by Cross-ministerial Strategic Innovation Promotion Program (SIP), “energy carrier” (Funding agency: JST). The Institute of Advanced Sciences (IAS) in Yokohama National University was supported by the MEXT Program for Promoting Reform of National Universities. We appreciate the person concerned them. References K. Ota, A. Ishihara, K. Matsuzawa, and S. Mitsushima, Electrochemistry, 78, 970 (2010).N. Itou, Hydrogen Energy Systems Society, 33, 9 (2008).S. Mitsushima, Y. Takakuwa, K. Nagasawa, K. Matsuzawa, Z. Awaludin, A. Kato, Y. Nishiki, Electrocatalysis, 7, 127 (2016). Figure 1