Hydrogen Reduction Reaction Research Articles

Enhanced catalytic activity of Ce1−xMxO2 (M = Ti, Zr, and Hf) solid solution with controlled morphologies

Ce(1-x)M(x)O(2) (M = Ti, Zr, and Hf) nanomaterials with controlled morphology and composition were synthesized by a two-step route for the first time. These nanomaterials exhibit high activities for hydrogen reduction and ethanol reforming reactions, and therefore, they may be useful for applications in catalysis and solid oxide fuel cells.

Proton transport in choline dihydrogen phosphate/H3PO4 mixtures

Mixtures of the plastic crystal material choline dihydrogen phosphate [Choline][DHP] and phosphoric acid, from 4.5 mol% to 18 mol% H(3)PO(4), were investigated and shown to have significantly higher proton conductivity compared to the pure [Choline][DHP]. This was particularly evident from the electrochemical hydrogen reduction reaction and the proton NMR diffusion measurements, in addition to ionic conductivity measured from the impedance spectroscopy. The ionic conductivity was observed to increase by more than an order of magnitude in phase I (i.e. the highest temperature solid phase in [Choline][DHP]) reaching up to 10(-2) S cm(-1). The multinuclear NMR spectroscopy data suggest that, at least on the timescale of the NMR measurement, the H(+) cations and [DHP] anions are equivalent in both phases. The pulsed field gradient NMR diffusion measurements of the 18 mol% acid sample indicate that all three ions are mobile, however the H(+) diffusion coefficient is an order of magnitude higher than for the [Choline] cation or the [DHP] anion, and therefore conduction in these materials is dominated by proton conductivity. The thermal stability, as measured by TGA, is unaffected with increasing acid additions and remains high; i.e. no significant mass loss below 200 °C.

Chemical transformation and morphology change of nickel–silica hybrid nanostructures via nickel phyllosilicates

Ni@SiO(2) core-shell nanoparticles were transformed to Ni particles on silica spheres via a branched nickel phyllosilicate phase by hydrothermal and hydrogen reduction reactions; the final morphology was successfully employed as an active nanocatalyst for the hydrogen transfer reaction of acetophenone.

The Impact of Trace Carbon Monoxide / Toluene Mixtures on PEMFC Performance

The impact of fuel impurities toluene (C7H8) and carbon monoxide (CO) on the performance of polymer electrolyte membrane fuel cells (PEMFCs) was investigated. Single and mixed impurities were injected into the fuel cell via the anode feed stream. Experiments were accompanied by gas chromatography analysis to determine the conversion and reaction processes occurring during contaminant exposure. Impurity injections of 2 and 20 ppm C7H8 caused an insignificant overpotential change of 2 and 8 mV respectively. An almost complete conversion of C7H8 to methylcyclohexane (C7H14) was observed. Impurity injections of 2 ppm CO caused a significant overpotential change of 247 mV. At steady state conditions more than 60% of the injected CO was converted to CO2 in the fuel cell. When the impurities were injected into the anode feed stream as a mixture the overpotential change was 100 mV greater than the sum of the overpotential changes the single impurities caused .Hydrogenation of C7H8 to C7H14 was observed but in contrast to the single C7H8 impurity experiment it stopped when a certain CO coverage was reached. The strong adsorption of CO caused a competition between the hydrogen reduction reaction and the hydrogenation of C7H8 for the available reaction sites.

Electroactive biofilms of sulphate reducing bacteria

Biofilms formed from a pure strain of Desulfovibrio desulfuricans 27774 on stainless steel and graphite polarised surfaces were studied. The polarisation conditions applied were −0.4 V vs. SCE for different times. A cathodic current related with the biofilms growth was observed with a maximum intensity of −270 mA m −2 that remained stable for several days using graphite electrodes. These sulphate reducing bacteria biofilms present electrocatalytic activity towards hydrogen and oxygen reduction reactions. Electrode polarisation has a selective effect on the catalytic activity. The biofilms were also observed by scanning electronic microscopy revealing the formation of homogeneous films on the surfaces.

The photocatalytic activity of TiO 2 foam and surface modified binary oxide titania nanoparticles

Surface modified titania dioxide composite nanoparticles prepared by hydrogen reduction reaction and a mesoporous TiO 2 foam made from a surface modifier and a long chain organic surfactant were characterized by diffractive, spectroscopic and microscopic techniques and studied for their catalytic activity towards the decomposition of an industrial water pollutant, methyl orange. The surface deposition of ruthenium and silicon particles improved the photocatalytic activity of the composite particles resulting in a faster decomposition of the methyl orange compared to commercial TiO 2 alone. Modification of TiO 2 with RuO 2 only offered a marginal benefit over TiO 2 while the incorporation of RuO 2 and SiO 2 into TiO 2 resulted in a marked increase in the rate constant and catalytic activity. These results are consistent with the enhanced surface properties of the composite materials resulting from the modification of TiO 2 with RuO 2 and SiO 2. This surface enhancement effects appear synergetic to the charge separation process and hence the photocatalytic results are explained on the basis of a mechanism involving efficient charge transfer across the interfaces of the composites involving photogenerated electron–hole pairs. Results obtained in this study show that the percentage degradation after 1 h of illumination was 47.15% for TiO 2 foam, 75.5 and 106.4%, respectively, for TiO 2/RuO 2 (SiO 2 5%, w/w) and TiO 2/RuO 2(SiO 2 10%, w/w) and 34.15% for commercial TiO 2.

Production of cobalt and nickel particles by hydrogen reduction

Cobalt and nickel nanoparticles were produced by hydrogen reduction reaction from cobalt or nickel chloride precursor vapour in nitrogen carrier gas. This aerosol phase method to produce nanoparticles is a scalable one-step process. Two different setups were introduced in particle production: a batch type reactor and a continuously operated reactor. Common feature in these setups was hydrogen mixing in a vertical flow reactor. The process was monitored on-line for particle mass concentration and for gas phase chemical reactions. Tapered element oscillating microbalance measured the particle mass concentration and Fourier transform infrared spectroscopy was used to monitor relevant gas phase species. The produced cobalt and nickel particles were characterised using transmission electron microscopy and x-ray diffraction. The produced cobalt and nickel particles were crystalline with cubic fcc structure. Twinning was often observed in cobalt particles while nickel particles were mostly single crystals. The cobalt particles formed typically long agglomerates. No significant neck growth between the primary particles was observed. The primary particle size for cobalt and nickel was below 100 nm.

Material characteristics of Ni–P–B electrodeposits obtained from a sulfamate solution

Material properties of Ni–P–B alloy electrodeposits obtained from a Ni sulfamate bath were investigated as a function of the contents of the P and B sources (H 3PO 3 and the dimethyl amine borane complex (DMAB), respectively) with/without additives of 35 mg/L and the duty cycle by analyzing the chemical composition, microstructure, microhardness results, residual stress and stress–strain curves. SCC (stress corrosion cracking) resistance for a Ni–P–B electrodeposit was assessed by using the C-ring test. It was found that P and B are incorporated competitively during an electrodeposition and the sulfur from an additive is codeposited into the electrodeposit. As the contents of the alloying element sources of P and B increased, the crystallinity and the grain size of the electrodeposit decreased. The effect of boron on the crystallinity and grain size was also relatively larger than the phosphorus. It was explained by a restraining force against a grain growth and an adsorption of DMAB. Introduction of an additive into the bath retarded the crystallization and grain growth, which may be attributed to a change of the grain growth kinetics by the additive adsorbed on the substrate and electrodeposit surfaces during an electrodeposition. Hardness change with the heat treatment temperature was explained by a NiP x and NiB y precipitation which effectively impeded a grain growth and a precipitate coarsening leading to a recrystallization and grain growth. Moreover it was found that grain size was refined leading to a hardness increase with an increase of the P and B contents, which is in good agreement with the Hall–Petch relation. With an increase of the duty cycle, the grain size increased leading to a decrease in the yield strength and tensile strength. This could be described by the relatively faster kinetics of the hydrogen reduction reaction. A Ni–P–B electrodeposit formed inside a tube by using an anode assembly showed an excellent SCC resistance suggesting that an electrodeposition inside a tube can be used as a SCC mitigation method.

In situ monitoring the effects of a magnetic field on the open-circuit corrosion states of iron in acidic and neutral solutions

The effects of a 0.4 T horizontal magnetic field (HMF) on the open-circuit corrosion states of iron in static aqueous solutions are studied by in situ monitoring the responses of two electrochemical parameters to the applied magnetic field, i.e. the open-circuit potential (OCP) and the current under potentiostatic polarization. The applied magnetic field makes the OCP shift in the noble direction. Withdrawing the magnetic field causes a negative shift of the OCP in acidic solutions, but it does not cause any significant change of OCP in neutral solutions. Imposing a magnetic field induces a cathodic current for iron that was previously potentiostatically polarized at the OCP without magnetic field. Withdrawing the magnetic field induces an anodic current for iron that was previously potentiostatically polarized at the OCP with the magnetic field. The magnetic field effect is more significant in the acid solutions than in the salt solutions. The magnetic field effects on the oxygen reduction and on the activation-controlled iron dissolution reaction are found to be insignificant. The magnetic field effect on the hydrogen reduction reaction on iron in acidic solutions is demonstrated. Results show the possibility that a magnetic field would affect the hydrogen evolution by enhancing the electron-transfer process that has been categorized in the classical electrochemistry kinetics to be the rate-determining process. The memory effect of the magnetic field on the electrochemical reaction is identified and discussed.

Effects of Certain Variables on the Materials Properties of Nickel Electrodeposits: Current Density and Duty Cycle

Alloy 600 tubing can be repaired by using a Ni electroplating to have an excellent SCC resistance. In order to carry out a successful Ni electrodeposition inside a steam generator tubing, the effects of various parameters on the material properties of the electrodeposit should be elucidated. Hence this work deals with the effects of the applied current density and the duty cycle(Ton / (Ton + Toff)) of the pulse current on the material properties of the Ni electrodeposit obtained from a Ni sulphamate bath by analyzing the current efficiency, the potentiodynamic curve, the hardness and the stress-strain curve. Hardness, YS(yield strength) and TS(tensile strength) decreased whereas the elongation increased as the applied current density increased. This was due to a concentration depletion of the nickel ion at the interface of the electrodeposit/solution, and a fractional decrease of the hydrogen reduction reaction. As the duty cycle increased, the hardness, YS and TS decreased while the elongation increased. During an off time at a high duty cycle, the concentration depletion of the nickel ion could not be sufficiently recovered and the fraction of the hydrogen evolution reaction which is kinetically faster than the nickel ion reduction decreased, which contributed to a coarse grain sized electrodeposit. The experimental results of the hardness and the stress-strain curves were supplemented by the results of the potentiodynamic curve.

Water electrolysis-induced optical degradation of aluminum-doped zinc oxide films

A type of optical degradation of aluminium-doped zinc oxide (AZO) films due to water electrolysis-induced reduction reaction was reported. An experiment was designed in which AZO films were immersed in a 0.01 M NaOH aqueous solution as cathode to electrolyze water. Significant decreases in the optical transmission of the treated samples were observed. Studies by X-ray diffraction and scanning electron microscope showed that the degradation of AZO films was due to compositional and structural changes with the treatment of water electrolysis, which resulted from the reduction reaction of atomic hydrogen generated in the electrolysis of water. This optical degradation reflects the stability degradation of AZO films under water electrolysis environment.

The use of Tafel back extrapolation to clarify the influence of ruthenium and palladium alloying on the corrosion behaviour of titanium in concentrated hydrochloric acid

Tafel back extrapolation of the cathodic reaction was used to interpret polarization data obtained for titanium alloyed with small amounts of ruthenium and palladium in concentrated hydrochloric acid. It was found that the ruthenium and palladium stimulated the cathodic reaction, but that the anodic behaviour of the titanium was unchanged. The results indicate that the corrosion of the titanium is increased by the small amount of alloying as the catalysis of the hydrogen reduction reaction was not strong enough to cause passivity of the titanium under these conditions. This was even so at longer times of exposure when significant enrichment of the ruthenium and palladium occurred on the surface of the titanium. Thermodynamic data were used to give further perspective to the results. Although excellent Tafel behaviour was found for the cathodic reaction, the exchange current densities and Tafel slopes obtained, are specific to the prior exposure time and surface enrichment of the alloying elements, and should not be interpreted as steady state data.

Effects of the peak current density and duty cycle on material properties of pulse-plated Ni–P–Fe electrodeposits

This work investigated the effects of the peak current density (PCD) and duty cycle of the pulse plating conditions on the material properties of the Ni–P–Fe electrodeposits obtained from a Ni sulphamate bath by analysing the chemical compositions, current efficiency, stress–strain curve and microstructure. Chemical compositions, the stress–strain curve and the microstructure were obtained using an inductively coupled plasma (ICP) mass spectrometer, tension tester and X-ray diffraction (XRD) and transmission electron micrograph (TEM), respectively. From the results of the stress–strain curves and the microstructure, as the peak current density increased, the yield strength (YS) and the tensile strength (TS) decreased, whereas the elongation and grain size increased. This is attributable to the concentration depletion at the interface of the electrodeposit/solution, the fractional decrease of the hydrogen reduction reaction and the decrease of the chemical concentration (Fe and P). As the duty cycle increased, the YS and the TS decreased while the elongation and grain size increased. During the off time at a high duty cycle, the concentration depletion could not be recovered sufficiently enough at the interface of the electrodeposit/solution, resulting in a coarse grain sized electrodeposit. It is also possible that the ductile electrodeposit can be obtained at a high duty cycle due to the relatively small hydrogen reduction reaction rate and the chemical concentration of the alloying elements. From the comparison between the stress–strain curves for the pulse-plated electrodeposits without an additive and the DC-plated electrodeposit with an additive, the enhancement of the nucleation rate caused by the recovery of the reacting species at the depleted interface during the off time of the pulse plating is comparable with the effect of the additive on the nucleation rate during a DC plating.

Effect of Additives on Hydrogen Evolution and Absorption during Zn Electrodeposition Investigated by EQCM

Hydrogen evolution and absorption during Zn electrodeposition from zinc sulfate electrolytes containing polyethylene glycol (PEG), gelatin, and thiourea (TU) was studied using an electrochemical quartz crystal microbalance (EQCM). The results obtained indicate that PEG and gelatin act as inhibitors of hydrogen absorption on the deposited Zn and that TU acts as an inhibitor of hydrogen evolution but yet promotes hydrogen absorption on the Zn deposits. Gelatin suppressed hydrogen reduction most effectively. EQCM proved to be a useful in situ tool for investigating the effects of hydrogen evolution and absorption on metal deposition and for distinguishing between the cathodic charge for Zn deposition and hydrogen reduction reaction.

A study on effect of hydrogen reduction reaction on the initial stage of Ni electrodeposition using EQCM

Electrodeposition of Ni from acidic sulfate solution with/without the addition of boric acid was studied by electrochemical quartz crystal microbalance (EQCM) to further investigate the initial stage of Ni deposition. EQCM analysis showed that nickel hydroxide was formed due to the pH increase near the electrode caused by hydrogen evolution in the absence of boric acid. In the presence of boric acid, nickel hydride was formed. EQCM was found to be a useful in-situ tool for investigating the effects of the evolution and absorption of hydrogen on metal deposition and separating the charge used for Ni deposition and for hydrogen reduction.

Via-Filling Capability of Copper Film by CVD

The via-filling properties of chemically-vapor-deposition (CVD) Cu film filled in deep submicrometer vias (diam of 0.11, 0.15 and 0.18 μm) were investigated with respect to various deposition parameters. A superior void-free via-filling by Cu film can be achieved at low temperature, low pressure, and high concentration of precursor species in the gas phase. However, these favorable conditions for void-free via-filling of Cu film also lead to slightly degraded film properties, including higher resistivity, higher content of impurities, degraded adhesion to substrate, and lower deposition rate, as compared with those obtained under the optimal deposition condition. Thus, a trade-off is needed between void-free via-filling and a superior film property. The key to achieve a void-free via-filling is to have a high probability of a re-emission event for the Cu-containing species inside the vias. Using helium (He) as the carrier gas is preferable to using hydrogen because the hydrogen reduction reaction would enhance the deposition of Cu, resulting in a decreased probability of a re-emission event and thus degrading the capability of void-free via-filling. In this study, we have achieved void-free filling by CVD Cu film in deep submicrometer 0.11 μm diam vias with an aspect ratio of 9.1 at and below deposition temperatures of 160°C, using a precursor flow rate of 0.4 cm3/min and at a deposition pressure of 60 mTorr. © 2003 The Electrochemical Society. All rights reserved.

H 2O-induced degradation in TiO 2-based ceramic capacitors

H 2O-induced degradation in TiO 2-based ceramic capacitors (rutile-based ceramic capacitor) was studied by means of the electrolysis of water. In the test, the ceramic capacitors were placed in a 0.01 M NaOH solution and a small dc voltage was applied to evolve hydrogen onto their silver electrodes. The samples treated by electrolysis of water showed obvious degradation as their permittivity decreased and their dielectric loss increased significantly. I– V measurements indicated that the resistance decreased greatly in the degraded samples. The decrease in resistance could be ascribed to the generation of charge carriers due to the reduction reaction of atomic hydrogen from the electrolysis of water. These results suggested that the reduction reaction of atomic hydrogen at ambient temperature was a cause of the degradation for the rutile ceramic capacitors.

Water‐Induced Degradation of Barium Titanate Ceramics Studied by Electrochemical Hydrogen Charging

Water‐induced degradation of barium titanate (BTO) ceramics has been investigated using electrochemical hydrogen charging, in which the silver electrodes of BTO ceramic specimens are made cathodes in a 0.01M NaOH solution to evolve hydrogen by electrolysis of water. After 80 h of treatment, the resistance of BTO decreases by ∼3 orders of magnitude, and the dielectric loss obviously increases. The degradation can be explained by the reduction reaction of atomic hydrogen with BTO. Hydrogen acts as a donor in BTO, and electrons are formed by the reduction. It is proposed that the reduction reaction of atomic hydrogen at ambient temperature by electrolysis of water is an important origin for degradation of BTO‐based ceramic devices.

Influence of electroless nickel plating on I– V characteristics and its implications for reliability in ZnO-based ceramic varistors

A comparison experiment was designed and carried out to study the influence of electroless nickel plating on ZnO-based ceramic varistors. It was found that the influence was not caused by permeation of the plating solution; the influence was directly related to nickel deposition. It is proposed that adsorbed hydrogen atoms generated in electroless plating can diffuse into ZnO ceramic varistors and undergo a reduction reaction with them, which result in a substantial increase in the leakage current of the varistors. Some implications for the influence of electroplating on I– V characteristics and for the long-term degradation of ZnO varistors are also discussed, in which much attention is paid to the reduction reaction of atomic hydrogen generated by electrolysis of water.

Electrochemical Reactivity of Zirconium-Based Bulk Metallic Glasses

ABSTRACTAmorphous Zr-(Ti)-(Nb)-Al-Cu-Ni alloy samples were prepared by melt-spinning and copper mould casting in an argon atmosphere and characterized regarding their microstructure and thermal behavior. Their anodization behavior in aqueous environments with pH= 0.5 – 13 was studied by electrochemical polarization techniques in combination with surface analytical investigations, i.e. SEM/EDX, AES. In chloride-containing solutions the macroscopic corrosion resistance of bulk amorphous alloys is affected by the presence of heterogeneities, such as concentrated cluster zones of selected components or crystalline defects. Pitting phenomena are studied in neutral and acidic chloride solutions and as a result a local corrosion mechanism is proposed. The cathodic reactivity of alloy samples at different microstructural states and after pre-etching in fluoride solutions was investigated. After pre-etching melt-spun amorphous samples exhibit a significant increase in surface reactivity as expressed by a drastic increase in electrochemical capacities and in cathodic current densities as well as by a significant reduction of overpotentials for the hydrogen reduction reaction. The hydrogen sorption behavior was studied on samples galvanostatically charged at various cathodic current densities by means of XRD, DSC, TEM and thermal desorption analysis TDA. At room temperature Zr-based alloys absorb hydrogen up to H/M=1.65 mainly by interstitial solution of hydrogen atoms in the amorphous structure. The effect of absorbed hydrogen on the thermal stability and the crystallization behavior is described.