Saturated KOH Research Articles

Steady State Performance Evaluation of Noble-Metal Free Bifunctional Electrode for Overall Water Splitting

The emerging need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency. This reaction takes place almost exclusively on Pt/C catalysts at the cathode which is expensive and need to be replaced by a metal-based catalyst that is cost effective and can show a comparable HER (Hydrogen Evolution Reaction) activity. Transition metal oxides, nitrides and sulfides have been widely explored as catalysts for HER and OER (Oxygen Evolution Reaction) due to their good electronic conductivity, stable and variable oxidation states, and superior corrosion resistance. In this research, MoNi4 embedded MoO3 nanorods are synthesized using facile hydrothermal method. Further, Molybdenum Vanadium Nitride is coated on top the synthesized electrode using RF/DC magnetron co-sputtering. This combination of hydrothermal and magnetron sputtering fabrication methods of the electrodes results in high surface area of the electrodes thereby improving the reaction kinetics of hydrogen production. The performance of the electrodes is tested in N2/O2 saturated 1M KOH solution using steady state technique called Staircase Voltammetry (SCV) instead of conventional dynamic LSV (Linear Sweep Voltammetry)/CV (Cyclic Voltammetry). This alternative method for testing is performed due to the exaggeration of the catalytic performance through conventional LSV/CV arising from double layer charging for nanostructured electrode. The electrodes are characterized by X-ray diffraction and SEM for structural and morphological analysis. Hence, we report the synthesis of novel MoVN on MoNi4/MoO2 nanorods using DC/RF Magnetron co-sputtering as an efficient, bifunctional, binder free electrode for overall water splitting. The electrode is characterised for both full-cell and half-cell configurations proving its stability for 12 hours. This work provides a reliable approach to the production of low cost and high-effectiveness electrodes for the application in commercial electrolyzers.

Engineering Transition Metals As Noble-Metal Free Bifunctional Electrode for Overall Water Splitting

The emerging need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency.[1] This reaction takes place almost exclusively on Pt/C catalysts at the cathode which is expensive and need to be replaced by a metal-based catalyst which can show a comparable HER (Hydrogen evolution reaction) activity. Transition metal oxides, nitrides and sulfides have been widely explored as catalysts for HER and OER (Oxygen evolution reaction) due to their good electronic conductivity, stable and variable oxidation states, and superior corrosion resistance.[2] In this research, MoNi4 embedded MoO3 nanorods are synthesized using facile hydrothermal method. Further, Molybdenum Vanadium Nitride is coated on top the synthesized electrode using RF/DC magnetron co-sputtering.[3] This combination of hydrothermal and magnetron sputtering fabrication methods of the electrodes results in high surface area of the electrodes thereby improving the reaction kinetics of hydrogen production. The performance of the electrodes is tested in N2/O2 saturated 1M KOH solution using steady state technique called Staircase Voltammetry (SCV) instead of conventional dynamic LSV (Linear sweep voltammetry)/CV (Cyclic Voltammetry).[4] This alternative method for testing is performed due to the exaggeration of the catalytic performance through conventional LSV/CV arising from double layer charging for nanostructured electrode. The electrodes are characterized by X-ray diffraction and SEM for structural and morphological analysis. Hence, we report the synthesis of novel MoVN on MoNi4/MoO2 nanorods using DC/RF Magnetron co-sputtering as an efficient, bifunctional, binder free electrode for overall water splitting. The electrode is characterised for both full-cell and half-cell configurations proving its stability for 12 hours. This work provides a reliable approach to the production of low cost and high-effectiveness electrodes for the application in commercial electrolyzers.[1] J. Zhang et al., “Efficient hydrogen production on MoNi4 electrocatalysts with fast water dissociation kinetics,” Nat. Commun., vol. 8, no. May, pp. 1–8, 2017, doi: 10.1038/ncomms15437.[2] L. A. Santillán-Vallejo et al., “Supported (NiMo,CoMo)-carbide, -nitride phases: Effect of atomic ratios and phosphorus concentration on the HDS of thiophene and dibenzothiophene,” Catal. Today, vol. 109, no. 1–4, pp. 33–41, 2005, doi: 10.1016/j.cattod.2005.08.022.[3] B. Wei et al., “Bimetallic vanadium-molybdenum nitrides using magnetron co-sputtering as alkaline hydrogen evolution catalyst,” Electrochemistry Communications, vol. 93. pp. 166–170, 2018, doi: 10.1016/j.elecom.2018.07.012.[4] S. Anantharaj and S. Kundu, “Do the Evaluation Parameters Reflect Intrinsic Activity of Electrocatalysts in Electrochemical Water Splitting?,” ACS Energy Lett., vol. 4, no. 6, pp. 1260–1264, 2019, doi: 10.1021/acsenergylett.9b00686. Figure 1

Phenol removal via activated carbon from co-pyrolysis of waste coal tar pitch and vinasse

The behavior and characteristics of phenol adsorption by activated carbon produced from co-pyrolysis of coal tar pitch and vinasse were investigated. Coal tar pitch and vinasse (mass ratio of 1:3) were firstly co-pyrolyzed and carbonated at 400 °C for 2 h. The carbonized material produced was then soaked with saturated KOH solution and activated at 800 °C for 1 h to form activated carbon. Results from the phenol wastewater adsorption experiments suggest that pseudo-second-order kinetics and the Weber-Morris model could reflect the time-dependent adsorption behavior of phenol wastewater by the activated carbon, revealing that internal diffusion represents the rate-limiting procedure and dominant process to control the adsorption rate in the early stage of the adsorption. Monolayer adsorption played the key role during the phenol adsorption. The adsorption was an endothermic reaction in temperature ranging from 15 °C to 35 °C, indicating that the adsorption speed could be stimulated by the increasing temperature. This study establishes a theoretical foundation for the usage and the potential application of the activated carbon derived from coal tar pitch and vinasse in wastewater treatment.

Electrochemical Oxygen Reduction Reaction Performance of Water Hyacinth Derived Porous Non-precious Electrocatalyst in Alkaline Media

This research studied the possibility of converting water hyacinth biomass into the porous non-precious oxygen reduction reaction (ORR) electrocatalyst using a simple, low cost and scalable autogenic pressure method. The electrocatalyst was prepared by thermally annealing water hyacinth root contained ZnCl2 at 700oC under autogenic pressure conditions. The phase of the catalyst was the mixture of carbon and metal oxide. In addition, rough surface morphology and high porosity were clearly observed using scanning electron microscope. The synthesized catalyst was then determined the ORR performance by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques under O2 saturated KOH solution. The ORR performance increased as the catalyst loading was increased and the optimum catalyst loading was found to be 1.5 mg/cm2 which generated the Eonset and E1/2 value of 0.93 V and 0.80 V vs. RHE, respectively. Furthermore, the E1/2 value of the synthesized catalyst was 230 and 130 mV greater than the catalyst synthesized without ZnCl2 and commercial carbon (VXC-72R). ORR durability study suggested that the prepared catalyst was durable to operate ORR for 5000 cycles in alkaline media. These results suggested that the autogenic pressure conditions would be a promising technique to prepare highly active and durable biomass derived ORR electrocatalyst.

(Invited) A Surface Enhanced Infrared Absorption Spectroscopy Study on the Nitrogen Electrochemical Reduction Reaction on Gold Surfaces

Ammonia has received much attention as a potential energy storage medium and an alternative fuel for vehicles, in addition to its use as a kind of fertilizer. Recent studies showed that ammonia could be produced by N2 and H2O through an electrochemical method, with the advantages of zero CO2 emission and energy saving compared with the “Haber-Bosch” process.1-2 However, as the theoretical potentials of hydrogen evolution reaction (HER) and nitrogen reduction reaction (NRR) are very close, H2 is the dominant product due to the much fast reaction kinetics of the former. For this reason, the experimental studies on NRR mechanism are rather rare. In this study, the NRR mechanism on Au surfaces was first studied by surface enhanced infrared absorption spectroscopy (SEIRAS) technique. Au was selected as its excellent NRR activity but low HER activity.3-4 An Au nanofilm deposited on the Si prism by a chemical deposition method was used as the working electrode. Its cyclic voltammograms (CV) in a N2 saturated KOH solution is shown in Figure 1a. In the 1st segment (cathodic scan, solid red line), the reduction current resulting from the HER and NRR appeared at 0 V and arose sharply starting at -0.1 V. Figure 1b is the corresponding FTIR spectra of the 1st segment in Figure 1a. The bands at 3300 cm-1 and 1645 cm-1 attribute to the O-H stretching and H-O-H bending of water molecules. Those bands intensity increase significantly as a result of the change in the adsorption configuration of water molecules upon decreasing the potential. The bands at 1450 cm-1, 1298 cm-1 and 1109 cm-1 attribute to the H-N-H bending, -NH2 wagging and N-N stretching of adsorbed N2Hy species, respectively. Those bands started to appear at potentials below 0 V and increased with potential decreasing. This result indicates that the nitrogen reduction reaction on Au surfaces follows an associative mechanism, and the N≡N bonds in N2 tend to break simultaneously with the hydrogen addition. Similar spectroscopic studies on Pt surfaces will be also discussed. Figure 1. a) Cyclic voltammograms of an Au film electrode deposited on the Si prism in a N2-saturated 0.1M KOH aqueous solution; potential scan rate: 2.5 mV s-1. b) FTIR spectra during the 1st segment from 0.4 V to -0.5 V on the Au film electrode in a N2-saturaed 0.1 M KOH solution. The reference spectrum was taken at 0.4 V. References Lan, R.; Irvine, J. T. S.; Tao, S. W. Sci Rep 2013, 3, 1145..Renner, J. N., Greenlee, L. F., Ayres, K. E., Herring, A. M. The Electrochemical Society Interface 2015, 24, 7, 51-57.Bao, D.; Zhang, Q.; Meng, F. L.; Zhong, H. X.; Shi, M. M.; Zhang, Y.; Yan, J. M.; Jiang, Q.; Zhang, X. B. Adv. Mater. 2017, 29, 1604799.Shi, M. M.; Bao, D.; Wulan, B. R.; Li, Y. H.; Zhang, Y. F.; Yan, J. M.; Jiang, Q. Adv. Mater. 2017, 29, 1606550. Figure 1

Evaluation of Order Mesoporous Carbon as Anode Catalyst for Microbial Fuel Cells Applications

Ordered Mesoporous Carbon (OMC) was evaluated as anode catalyst in a MFC. Bacilus subtilis (B. subtilis) was the microorganism, while the electrolyte was Pharmaceutical Residual Water (PRW). In a dual chamber MFC, the anode and cathode compartments contained N2–saturated PRW and O2–saturated KOH (both electrolytes with pH=9.6), respectively, separated by a Nafion® membrane. The anode catalysts on gas diffusion electrodes in the MFC were: methanol-functionalized OMC, non-functionalized OMC, methanol-functionalized Vulcan XC-72 and commercial Pt/C, all covered by a biofilm of B. Subtilis. Meanwhile, the cathode catalyst was Pt/C. Significantly higher catalytic activity was obtained from functionalized OMC + B. Subtilis in the MFC. The Open Circuit Voltage (OCV) was 0.58 V, with a maximum current density (jcell) of 854 mA m-2. These values were 2.6 and 4.7 times higher than those from Pt/C. The results showed that methanol-functionalized OMC is a metal-free catalyst with high performance for MFCs.

Novel highly active and selective Fe-N-C oxygen reduction electrocatalysts derived from in-situ polymerization pyrolysis

Among several candidates considered to replace expensive platinum based catalysts for oxidation reduction reaction (ORR) in fuel cells, iron-nitrogen-carbon (Fe-N-C) composites attract the most interest. In this work, we design a novel method to prepare Fe-N-C catalysts for ORR in both acid and alkaline media. It involves initial polymerization of different amino-pyridines to form a C-N-C backbone, followed by their high-temperature pyrolysis on silica template, HF etching and second heat treatment in ammonia. Polymerization of 2-amino-6-methylpyridine and 2,6-diaminopyridine was done by in-situ and ex-situ templating methods. The catalysts synthesized by this method possess half-wave potentials of ~ 0.88V versus RHE in O2 saturated 1M KOH electrolyte, and the best catalyst based on 2-amino-6-methylpyridine was seen to achieve an E1/2 greater than 0.7V in the O2 saturated 0.5M sulfuric acid electrolyte. Importantly, the catalysts prepared by this novel method exhibit remarkably low peroxide yield in both acid and base media (< 4% and < 1.3%, respectively) as revealed by rotating ring disk electrode (RRDE) studies.

Nitrogen-Incorporated Amorphous Carbon Catalysts with Higher Reactivity toward Oxygen Reduction Reaction

Introduction One of the challenges to be addressed in facilitating widespread dissemination of polymer electrolyte fuel cell (PEFC) is to reduce the amount of Pt catalysts used in PEFC. The rate of oxygen reduction reaction (ORR) (O2 + 2H+ + 4e- → 2H2O) is relatively lower at Pt surface and quite a large amount of Pt catalysts is required to increase O2 reduction rate, which is a serious problem for cathode electrodes. For instance, 100g of Pt is needed for a fuel cell vehicle. Pt usage of this sort is impractical in terms of resources as well as economics. In order to ensure widespread commercialization of PEFC, the development of non-Pt catalysts is essential. The other challenge is to improve the stability of catalysts. The activity of Pt catalysts is known to be decreased by surface poisoning during long-term use. The objective of this study is to realize non-Pt catalyst with ORR activity and higher stability by using amorphous carbon (a-C) incorporating nitrogen atoms. It has been reported that carbon alloy with quinolizinium structure at graphene edges exhibited the higher ORR activity [1]. Our research group has reported that a-C including amorphous phase and nano-sized sp 2 cluster could be a conductive material by incorporating nitrogen atoms. It works as an ideal polarizable electrode with higher overpotential toward water discharge and higher stability to electrochemically-induced corrosion [2]. In the study, a-C based catalysts with higher ORR activity and higher stability was tried to be realized by introducing quinolizinium structure at the sp 2cluster surface in a-C. Experimental a-C catalysts with quinolizinium structure were synthesized by plasma-enhanced CVD method. Vaporized acetonitrile + pyridine (6:4 at a molar ratio) mixture was used as a source material. a-C catalysts were synthesized under various conditions of RF power and substrate temperature. Chemical compositions and structures of the resulting a-C were examined by XPS and Raman spectroscopy. The reactivity of ORR was examined by linear sweep voltammograms using rotating disk electrode (RDE). Results and Discussion The size of sp 2 clusters of the resulting a-C catalysts was estimated from Raman spectra. The ratios of sp 2/sp 3-hybridized carbons and the density of N atoms in quinolizinium structure were estimated from XPS results. Hydrodynamic voltammograms using RDE (Figure 1) were carried out to estimate the number of electrons for O2 reduction in O2 saturated 1M KOH solution. The peak correspond to N atoms in quinolizinium structure (graphitec N) was included in N1s peak in XPS spectra of all a-C catalysts and observed at approximately 402 eV. These results indicate that functional groups active for O2 reduction are introduced in graphite regions in a-C. With increasing RF power of CVD synthesis, the ratio of sp 2/sp 3 from XPS exhibited a tendency to increase, the size of sp2 cluster to decrease, and the density of N atoms in quinolizinium structure to increase. It indicates that the active site for O2 reduction can be controlled by deposition condition. The number of electrons for O2 reduction was enhanced by these structural changes and reached 2.82 at a maximum (Figure 1). The value over 2 suggests that a-C catalysts with the activity of 4-electron ORR were successfully realized. It can be expected that the ORR activity is further enhanced by optimizing sp 2/sp 3, the size of sp 2cluster, and the density of N atoms in quinolizinium structure.

Conversion of electrodeposited Co(OH)2 to CoOOH and Co3O4, and comparison of their catalytic activity for the oxygen evolution reaction

Cobalt hydroxide, β-Co(OH)2, was electrodeposited cathodically from an alkaline solution of tris(ethylenediamine)cobalt(III). The Co(OH)2 crystals grew into a microcone morphology and the surface became CoOOH at anodic potentials. The Co(OH)2 film was fully converted to CoOOH by electrochemical oxidation at 95°C in 1M KOH and to Co3O4 by thermal decomposition at 300°C in air. The Co(OH)2 and CoOOH films grew with a [001] orientation on Au(111), and the converted Co3O4 films had a [111] orientation. The overall morphology was retained upon conversion. However, an increase in roughness was observed on the surface of the CoOOH and Co3O4 microcones. The electrochemically active area of the films was estimated from double layer capacitance measurements in acetonitrile with tetrabutylammonium hexafluorophosphate electrolyte. The CoOOH had a roughness factor of 9.4, and the Co3O4 had a roughness factor of 63.6. The catalytic activities of the films for the oxygen evolution reaction (OER) were compared by Tafel analysis in an O2 saturated 1M KOH at room temperature. The CoOOH and Co3O4 films appeared to exhibit different Tafel behavior with Co3O4 being the superior catalyst when the geometric area was used in the Tafel analysis. However, when the observed current densities were corrected for the measured electrochemically active areas, the linear regions of the two Tafel plots fell on the same line. The results suggest that the active species, likely Co(IV), for the OER is the same on both materials. Both CoOOH and Co3O4 had a Tafel slope of 60mV dec−1 and an exchange current density of 6.1×10−11 A cm−2. The conversion method outlined in the paper provides a means to produce Co3O4 with a large electrochemically-active area.

Manganese Dioxide-based Bifunctional Oxygen Reduction/Evolution Electrocatalysts: Effect of Perovskite Doping and Potassium Ion Insertion

Non-precious metal bifunctional oxygen reduction and oxygen evolution reaction (ORR and OER, respectively) catalysts are of great interest for rechargeable metal/air batteries and regenerative alkaline fuel cells. We investigate the initial stage activities and the electrocatalytic durability of bifunctional catalysts composed of MnO2 and perovskite (LaNiO3 or LaCoO3) in a 1:1 weight ratio. Gas diffusion electrodes (GDE) with a catalyst layer composed of MnO2:co-catalyst (LaNiO3 or LaCoO3):Vulcan XC-72 were prepared and studied in O2 saturated 6M KOH. The initial stage bifunctional activities of MnO2-LaCoO3 and MnO2-LaNiO3 are markedly superior compared to either MnO2 or perovskite alone, demonstrating a synergistic effect. Furthermore, we show for the first time that the degradation of the bifunctional electrocatalytic activity of the MnO2-perovskite electrodes during extensive potential cycling can be fully restored by resting the electrodes at open-circuit potential in 6M KOH. A hypothesis is proposed to explain this catalytic promotion and ‘healing’ effect based on XPS results showing potassium ion incorporation in the electrocatalyst structure. Lastly, a thorough comparison of the results obtained in the present work with those reported in the literature with a variety of bifunctional catalysts is presented, demonstrating the effectiveness of the MnO2-perovskite electrodes.

Solubility Data for the KOH–K2CO3–K3VO4–H2O System at (313.15 and 353.15) K

The effective separation of K3VO4 and K2CO3 from KOH-K2CO3-K3VO4-H2O system plays an important role in a new vanadium production process developed by the Institute of Process Engineering, Chinese Academy of Sciences. In order to design an effective separation strategy, the dissolution behavior of K3VO4 and K2CO3 in KOH-K2CO3-K3VO4-H2O system at (313.15 and 353.15) K was investigated, and the solubility isotherms were plotted. In addition, the solubility of K3VO4 in KOH solutions was compared with that in K2CO3 saturated KOH solutions, and the solubility of K2CO3 in KOH solutions was also compared with that in K3VO4 saturated KOH solutions. From the solubility data analysis, a method of first separation K2CO3 via cooling crystallization followed by separation K3VO4 via cooling crystallization in the concentrated alkaline solution was proposed.

Magnesium nanopowder for hydrogen absorption and ammonium perchlorate decomposition

Magnesium nanopowder (MgNP) of 17nm average size was produced by planetary ball milling of Mg (ϕ=229μm) with 10wt% NaCl (ϕ=406μm) for 50h. NaCl was omissible by dissolution in saturated KOH. Partial oxidation of MgNP occurred, however, in presence of KOH. MgNP–NaCl mixture was, therefore, used for transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), differential scanning calorimetry (DSC) and Sieverts equilibrium investigation. DSC analysis of ammonium perchlorate showed one endothermic and three exothermic reactions. MgNP did not noticeably affect on the initial endothermic reaction. But it decreased transformation temperatures of the second and the third exothermic reactions and increased their heat generation. MgNP 10% NaCl mixture absorbed hydrogen and showed depressing effect on NH4ClO4 decomposition temperature more than initial Mg micropowder.

Degradation and Pathway of Tetracycline Hydrochloride in Aqueous Solution by Potassium Ferrate

In the context of water treatment, the ferrate ([FeO(4)](2-)) ion has long been known for its strong oxidizing power and for producing a coagulant from its reduced form [i.e., Fe(III)]. However, it has not been widely applied in water treatment, because of preparation difficulties and high cost. This article describes a low-cost procedure for producing solid potassium ferrate. In this synthetic procedure, NaClO was used in place of chlorine generation; and 10 M KOH was used in place of saturated KOH in the previous procedures. In addition, this study investigated the reactions of potassium ferrate with tetracycline hydrochloride (TC) at different pH and molar ratios. Results showed that the optimal pH range for TC degradation was pH 9-10, and TC could be mostly removed by Fe(VI) in 60 s. However, results showed >70% of TC degraded and <15% of dissolved organic carbon (DOC) reduction at molar ratio of 1:20. The main degradation pathway of TC is proposed based on the experimental data.

Use Differential Pulse Voltammetry for Determining the 2,6-Ditertbutyl-4-Methylphenol in Jet Fuels

A new method for determination of antioxidants in jet fuels, which is based on the differential pulse voltammetric characteristics of the antioxidant 2,6-ditertbutyl-4-methylphenol in the solution of saturated KOH anhydrous ethyl alcohols, is established. The experimental results have shown that there is a linear relationship between the content of 2,6-ditertbutyl-4-Methyl-phenol in the jet fuel and the differential pulse voltammetry response in the electrolytic solution. It has also been shown that the antioxidant contents can be reliably and simply determined with the help of the standard addition method. The largest relative error of the determination is 6.70 %, the biggest confidence for 5 samples is 1.95 mg/L (n=5, 95% confidence level).

Seedless Copper Electrodeposition onto Tantalum Diffusion Barrier by Two-Step Deposition Process

Copper was electrodeposited directly onto a 5 nm thick physical vapor deposited tantalum (Ta) diffusion barrier layer in a copper-ammonium-citrate (Cu-NH 3 -Cit) bath. An anodic potential was applied to Ta in a saturated KOH solution to remove native Ta oxide before seedless copper deposition on Ta. The dense growth of copper films with sufficient wetting and adhesion on Ta was made possible by a two-step potentiostatic deposition at -1.26 V vs saturated calomel electrode (SCE) for Cu 2 (Cit) 2 OH 3- ion reduction and then at -0.58 V vs SCE for cupric ion reduction.

Liquid-phase hydrodechlorination of chlorobenzene by molecular hydrogen: The influence of reaction medium on process efficiency

Catalytic hydrodechlorination (HDCl) of chlorobenzene was carried out in a two-phase aqueous–organic solvent system and a single-phase solvent composed of saturated KOH solution in a secondary alcohol over Pd-based catalysts at 50 °C and atmospheric pressure of H2. It was shown that an aqueous–organic solvent system containing propan-2-ol and aqueous KOH increases catalyst activity by promoting mass transfer of the formed chloride ions to water phase that prevents catalyst deactivation. It is inferred that propan-2-ol favors hydrogen activation during the HDCl process. Use of the Pd catalysts based on hydrophobic carbon support enables chlorobenzene HDCl to proceed in a two-phase solvent at a satisfactory rate, even in the absence of phase-transfer catalysts.

Crystal Structure of Biotin Carboxylase in Complex with Substrates and Implications for Its Catalytic Mechanism

Biotin-dependent carboxylases are widely distributed in nature and have important functions in many cellular processes. These enzymes share a conserved biotin carboxylase (BC) component, which catalyzes the ATP-dependent carboxylation of biotin using bicarbonate as the donor. Despite the availability of a large amount of biochemical and structural information on BC, the molecular basis for its catalysis is currently still poorly understood. We report here the crystal structure at 2.0 A resolution of wild-type Escherichia coli BC in complex with its substrates biotin, bicarbonate, and Mg-ADP. The structure suggests that Glu(296) is the general base that extracts the proton from bicarbonate, and Arg(338) is the residue that stabilizes the enolate biotin intermediate in the carboxylation reaction. The B domain of BC is positioned closer to the active site, leading to a 2-A shift in the bound position of the adenine nucleotide and bringing it near the bicarbonate for catalysis. One of the oxygen atoms of bicarbonate is located in the correct position to initiate the nucleophilic attack on ATP to form the carboxyphosphate intermediate. This oxygen is also located close to the N1' atom of biotin, providing strong evidence that the phosphate group, derived from decomposition of carboxyphosphate, is the general base that extracts the proton on this N1' atom. The structural observations are supported by mutagenesis and kinetic studies. Overall, this first structure of BC in complex with substrates offers unprecedented insights into the molecular mechanism for the catalysis by this family of enzymes.

Optimization of Lycopene Extraction from Tomato Cell Suspension Culture by Response Surface Methodology

Radioisotope-labeled lycopene is an important tool for biomedical research but currently is not commercially available. A tomato cell suspension culture system for the production of radioisotope-labeled lycopene was previously developed in our laboratory. In the current study, the goal was to optimize the lycopene extraction efficiency from tomato cell cultures for preparatory high-performance liquid chromatography (HPLC) separation. We employed response surface methodology (RSM), which combines fractional factorial design and a second-degree polynomial model. Tomato cells were homogenized with ethanol, saponified by KOH, and extracted with hexane, and the lycopene content was analyzed by HPLC-PDA. We varied five factors at five levels: ethanol volume (1.33-4 mL/g); homogenization period (0-40 s/g); saturated KOH solution volume (0-0.67 mL/g); hexane volume (1.67-3 mL/g); and vortex period (5-25 s/g). Ridge analysis by SAS suggested that the optimal extraction procedure to extract 1 g of tomato cells was at 1.56 mL of ethanol, 28 s homogenization, 0.29 mL of KOH, 2.49 mL of hexane, and 17.5 s vortex. These optimal conditions predicted by RSM were confirmed to enhance lycopene yield from standardized tomato cell cultures by more than 3-fold.

Optimization of Lycopene Extraction from Tomato Cell Culture

For biomedical research, radioisotope‐labeled lycopene is important but not commercially available. A tomato cell suspension culture system for the production of radioisotope‐labeled lycopene was previously developed in our laboratory. In this study, our aim was to improve the lycopene extraction efficiency from the tomato cell culture. We employed the response surface methodology (RSM) which combines fractional factorial design and a second‐degree polynomial model. Tomato cells were homogenized with ethanol, saponified by KOH, extracted by hexane, and the lycopene content was analyzed by HPLC. We varied five factors with five levels: ethanol volume (4–12 mL); homogenization period (0–120 second); saturated KOH solution volume (0–2 mL); hexane volume (5–9 mL); and vortex period (15–75 second). RIDGE analysis by SAS suggested that the optimal extraction procedure employed 9.5 mL ethanol, 75 seconds homogenization, 0.94 mL KOH, 6.4 mL hexane, and 36 seconds vortex to yield lycopene 13.9 nmol lycopene /g from 3 g tomato cells. By repeating this predicted condition, the improvement of extraction yield was confirmed. The production of radioisotope‐labeled lycopene was more efficient and economical with improvement of the extraction procedure by RSM.

Quantitative Measurement of Interfacial Adhesion Between Seedless Electrodeposited Copper and Tantalum-Based Diffusion Barriers for Microelectronics

Seedless electrochemical deposition (ECD) can generate good adhesion of copper on TaN and Ta diffusion barriers using a saturated KOH solution and a copper-citrate complex electrolyte. The interfacial fracture energy of the Cu/TaN or Ta interface was quantitatively measured by four-point bending method. The load increased linearly with interfacial crack growth due to the plasticity of ductile copper and the elastic bending of the Si substrate. The delamination energy was proportional to the thickness of seedless ECD copper, which was in the range of 180-980 nm. The delamination energy in the steady state, G ss , of 5-24 J m -2 was attained.