Hydrogen Reduction Reaction Research Articles

Impact Electrochemistry of Layered Transition Metal Dichalcogenides.

Layered transition metal dichalcogenides (TMDs) exhibit paramount importance in the electrocatalysis of the hydrogen evolution reaction. It is crucial to determine the size of the electrocatalytic particles as well as to establish their electrocatalytic activity, which occurs at the edges of these particles. Here, we show that individual TMD (MoS2, MoSe2, WS2, or WSe2; in general MX2) nanoparticles impacting an electrode surface provide well-defined current "spikes" in both the cathodic and anodic regions. These spikes originate from direct oxidation of the nanoparticles (from M(4+) to M(6+)) at the anodic region and from the electrocatalytic currents generated upon hydrogen evolution in the cathodic region. The positive correlation between the frequency of the impacts and the concentration of TMD nanoparticles is also demonstrated here, enabling determination of the concentration of TMD nanoparticles in colloidal form. In addition, the size of individual TMD nanoparticles can be evaluated using the charge passed during every spike. The capability of detecting both the "indirect" catalytic effect of an impacting TMD nanoparticle as well as "direct" oxidation indicates that the frequency of impacts in both the "indirect" and "direct" scenarios are comparable. This suggests that all TMD nanoparticles, which are electrochemically oxidizable (thus capable of donating electrons to electrodes), are also capable of catalyzing the hydrogen reduction reaction.

Inhibition Performance Study of Aqueous Vanadate Species on Mg Alloys

This work presents the corrosion inhibition performance of vanadate on Mg alloy AZ31 and its dependence on pH and immersion time. Aqueous vanadate speciation, which has been shown to have a strong effect on corrosion inhibition, is a function of solution pH. The pH dependence of vanadate corrosion inhibition is, therefore, attributed to the pH dependence of vanadate speciation. Immersion in tetrahedrally coordinated vanadate species, present in neutral and alkaline solution, was shown to decrease corrosion rate and increase pitting potential, both of which were enhanced with longer immersion times. Alternatively, exposure to octahedrally coordinated vanadate, which predominates in acidic solution, only slightly decreased the corrosion rate. An acidic solution (octahedrally coordinated speciation) was adjusted to alkaline conditions and samples were then immersed in the adjusted alkaline solution. Inhibition on these samples was weaker than that of samples immersed in alkaline solutions that had never been acidic. Regardless of speciation, vanadate was shown to provide limited inhibition on cathodic reaction kinetics (hydrogen reduction reaction). Anodic inhibition was observed on samples treated in solutions containing tetrahedral species. Inhibition performance was also characterized by electrochemical impedance spectroscopy. Aqueous vanadate in 0.1 M NaCl increased the total impedance at all pH values (5, 7.7, 9.2), with enhanced results observed with increasing immersion time. The greatest increase in impedance for a given immersion time occurred at pH 9.2, which is consistent with the inhibition determined by corrosion rate. SEM showed that vanadate forms a film across both secondary particles and the Mg matrix, and it provided qualitative evidence that inhibition efficiency increased as the pH of the exposure solution increased. XPS results indicate that vanadate film formation is associated with the reductive adsorption of vanadate by Mg. Exposure at a pH of 5 produced vanadate predominated by V4+. Exposure at pH values of 7.7 and higher, however, produced vanadate containing predominantly V3+.

Electrochemical Devices Based on Solid Acid Electrolytes for Conversion of Methane Derivatives

A boom in natural gas production in the United States presents opportunities for economically effective use of methane-derived molecules. In contrast with methane gas, derivatives may exhibit advantages in volumetric energy density, ease of transport and versatility. Electrochemical conversion of these species to electricity and other fuels is desirable, but depending on the system in question, catalyst stability, activity, and impurity intolerance, or alternately, the cost and durability of the electrolyte may be impediments to adoption The solid-state proton conductor cesium dihydrogen phosphate (CsH2PO4 or CDP) has shown potential in electrochemical devices operating on fuels such as reformed NG or methanol. CDP undergoes a solid-solid phase transition at 228 °C and an associated increase in proton conductivity of more than three orders of magnitude (8.5 x 10-5 S cm-1 at 223 °C to 2.5 x 10-2 S cm-1 at 250 °C). These systems have been shown to tolerate reformate streams in H2-air cells containing CO, H2S, NH3, CH3OH, C3H8 and CH4 of 20%, 100ppm, 100 ppm, 5%, 3% and 5% respectively, retaining 90-95% of pure H2 performance1. Solid acid fuel cells operated using methanol and an integrated steam reformer have also shown similar results2. Recently, we showed that this material can also be used in an electrochemical hydrogen separation system using similar reformate streams3. In the majority of these earlier studies, platinum was used as the catalyst for both the hydrogen reduction and oxidation reactions. We have also demonstrated that unsupported nickel is an effective hydrogen evolution catalyst in solid acid hydrogen pump devices4. Here, we have synthesized a suite of carbon-supported non-platinum catalysts (Pt, Pd, Ru, Ni and Cu) for implementation in electrodes. We evaluate these materials as hydrogen oxidation and evolution catalysts in CDP-based devices for electricity and fuel production from the methane derivatives methanol and dimethyl ether. This work is supported by the National Science Foundation through TN-SCORE (EPS-1004083). References 1 C. R. I. Chisholm et al., Electrochem. Soc. Interface, 18, 53–59 (2009). 2 T. Uda, D. a. Boysen, C. R. I. Chisholm, and S. M. Haile, Electrochem. Solid-State Lett., 9, A261 (2006). 3 A. B. Papandrew et al., J. Electrochem. Soc., 161, F679–F685 (2014). 4 A. B. Papandrew, T.A. Zawodzinski Jr., J. Power Sources 245 (2014) 171. Figure 1

The Electrochemical Corrosion Behavior of High Strength Carbon Steel in H2S-Containing Alkaline Brines

In-situ electrochemical measurements were performed during the corrosion tests of high-strength low-alloy steel, grade S-135, used as a drill pipe in oil and natural gas exploration, in 5 % mass NaCl(aq) solutions of pH 7.5, 10.5, and 12.3 at 85 °C. For each pH, four concentrations of H2S were investigated which corresponded to one dose of H2S gas at H2S partial pressure, P H2S, equal to 0, 0.12 psi (0.83 kPa), 1.2 psi (8.3 kPa), and 10 psi (69 kPa), respectively. It was found that the corrosion process generally reached a steady state by 60 hours in a stirred solution. For P H2S = 0 and 0.12 psi (0.83 kPa), the polarization resistance (R pol) increased as pH increased from 7.5 to 12.3; however, R pol at pH 10.5 were the lowest for P H2S 1.2 psi (8.3 kPa) and 10 psi (69 kPa). The lower and moderate H2S concentrations (P H2S 0.12 psi and 1.2 psi) were generally found to give larger R pol values than without or high H2S levels (P H2S 0 psi and 10 psi) at each pH. The corrosion rates were inversely proportional to R pol and ranged on the orders of 0.001 to 0.1 mm/year. The change of pH had a larger effect on the corrosion rate than the change of H2S concentration. It is believed that higher pH suppressed the hydrogen reduction reaction by decreasing available proton sources and, therefore, resulted in higher R pol. Besides pH, the corrosion rate was also affected by the nature of the corrosion product film on the surface. The corrosion films were predicted with Pourbaix diagrams and investigated with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). With the pH increase from 7.5 to 12.3, the major products in the corrosion film generally changed from iron sulfides to iron oxides, which agreed with the Pourbaix diagrams. The morphology of the corrosion products was also believed to have influenced the protectiveness of the films. The change in R pol and corrosion rate was consistent with the change in the electrochemical impedance spectroscopy (EIS) behavior. Two time constants were generally observed in the Bode plots and the plots of pH 10.5 tended to have the time constants at higher frequencies than pH 7.5 and 12.3.

A Review of Corrosion and Hydrogen Diffusion Behaviors of High Strength Pipe Steel in Sour Environment

A brief overview is given of the corrosion and hydrogen diffusion behaviors of high strength pipe steel in sour environment. Firstly, hydrogen adsorption and diffusion mechanism of the pipe steel is introduced. Secondly, the effect of iron sulfide film precipitated as a result of the corrosion reaction on the steel surface on hydrogen reduction reaction and subsequent hydrogen permeation through the steel is discussed. Moreover, the hydrogen diffusion behavior of the pipe steel under tensile stress in both elastic and plastic ranges is reviewed based on a number of experimental permeation data and theoretical models describing the hydrogen diffusion and trapping phenomena in the steel. It is hoped that this paper will result in significant academic contributions in the field of corrosion and hydrogen related problems of the pipe steel used in sour environment.

Electrochemically active nickel foams as support materials for nanoscopic platinum electrocatalysts.

Platinum is deposited on open-cell nickel foam in low loading amounts via chemical reduction of Pt cations (specifically, Pt(2+) or Pt(4+)) originating from aqueous Pt salt solutions. The resulting Pt-modified nickel foams (Pt/Ni foams) are characterized using complementary electrochemical and materials analysis techniques. These include electron microscopy to examine the morphology of the deposited material, cyclic voltammetry to evaluate the electrochemical surface area of the deposited Pt, and inductively coupled plasma optical emission spectrometry to determine the mass of deposited Pt on the Ni foam substrate. The effect of potential cycling in alkaline media on the electrochemical behavior of the material and the stability of Pt deposit is studied. In the second part of this paper, the Pt/Ni foams are applied as electrode materials for hydrogen evolution, hydrogen reduction, oxygen reduction, and oxygen evolution reactions in an aqueous alkaline electrolyte. The electrocatalytic activity of the electrodes toward these processes is evaluated using linear sweep voltammetry curves and Tafel plots. The results of these studies demonstrate that nickel foams are acceptable support materials for nanoscopic Pt electrocatalysts and that the resulting Pt/Ni foams are excellent electrocatalysts for the hydrogen evolution reaction. An unmodified Ni foam is shown to be a highly active electrode for the oxygen evolution reaction.

Study of the composition, corrosion, and catalytic properties of Co-W alloys electrodeposited from a citrate pyrophosphate electrolyte

This study describes the composition of Co-W alloy coatings deposited from a citrate-pyrophosphate electrolyte, as well as the effect of the surfactants (SAS) on the quality, morphology, and properties of the coatings obtained. High corrosion resistance of the alloys on the order of 10−5 A cm−2 in a chloride solution and 10−3 A cm−2 in a 6.0 M L−1 KOH solution has been exhibited. The electrocatalytic activity in the reduction reaction of hydrogen in an alkaline medium has been studied, and a substantial decrease of the hydrogen overvoltage as compared to pure cobalt has been established.

Hydrogen permeation in high strength steel under load in aqueous environment

The hydrogen assisted cracking problem is one of the major causes of the failure occurring in the high strength steel structures used in various industries. In aqueous environment, hydrogen is generated by the hydrogen reduction reaction on the steel surface. With depletion of the high quality resources in oil and gas industry, the hydrogen assisted cracking problem becomes severe in sour environment, which contains high amount of H2S. Understanding on the hydrogen permeation behaviour is crucial to deal properly with the hydrogen related problems since they are primarily determined by the hydrogen uptake and transport in the steel. The Devanathan–Stachurski method is widely used to evaluate electrochemically the hydrogen permeation behaviour. This method has been successfully used for the steel with no load. Under loading condition, this electrochemical test method has been modified to accommodate the externally applied load. However, the data require careful examination to validate the technical importance because of the stability and homogeneity of palladium layer coated on the steel surface under load. In this paper, the hydrogen permeation test method under loading condition will be reviewed for the high strength steels used in oil and gas industry. The factors affecting the hydrogen permeation in the high strength steel will be discussed in terms of the applied stress level and the sulphide film forming on the steel surface in sour environment.

The unexpected activity of Pd nanoparticles prepared using a non-ionic surfactant template

Pd deposits on vitreous carbon substrates were prepared by electrodeposition from liquid crystal phases (both micellar and hexagonal phases) consisting of self-assembled non-ionic surfactant molecules. The morphology of the deposits varied significantly with the concentration of the surfactant but all are made up of aggregated nanoparticles circa 9 nm in diameter. The deposits from the micellar phase of the surfactant offer the largest electroactive area and specific activity for the hydrogen evolution, oxygen evolution and reduction reactions and formic acid and ethanol oxidations. Unexpectedly the deposits lead to an increase in catalytic activity far in excess of that expected from an enhancement in electroactive area.

Catalyst Induced Hydrino Transition (CIHT) electrochemical cell

SUMMARY Atomic hydrogen is predicted to form fractional Rydberg energy states H(1/p) called ‘hydrino atoms’ wherein n = 1/2,1/3,1/4,…,1/p (p ≤ 137 is an integer) replaces the well-known parameter n = integer in the Rydberg equation for hydrogen excited states. The transition of H to a stable hydrino state H[aH/p = m + 1] having a binding energy of p2 × 13.6 eV occurs by a nonradiative resonance energy transfer of m × 27.2 eV (m is an integer) to a matched energy acceptor such as nascent H2O which has a potential energy of 81.6 eV (m = 3) to form an intermediate that decays with the emission of continuum bands with short wavelength cutoffs and energies of m2 × 13.6 eV. The predicted H(1/4) continuum radiation in the region 10 to 30 nm was observed first at BlackLight Power, Inc. (BLP) and reproduced at the Harvard Center for Astrophysics (CfA) wherein H2O catalyst was formed by a hydrogen reduction reaction at the anode of a hydrogen pinch plasma. By the same mechanism, the nascent H2O molecule formed by an oxidation reaction of OH− at a hydrogen anode is predicted to serve as a catalyst to form H(1/4) with an energy release of 204 eV compared to the 1.48 eV required to produce H from electrolysis of H2O. CIHT cells, each comprising a Ni anode, NiO cathode, a LiOH–LiBr eutectic mixture as the electrolyte, and MgO matrix exploit hydrino formation as a half-cell reaction to serve as a new electrical energy source. The cells were operated under intermittent H2O electrolysis to generate H at the anode and then discharged to form hydrinos wherein trace H2O vapor was supplied as entrained in an inert gas flow in otherwise closed cells. Net electrical production over the electrolysis input was measured using an Arbin BT 2000 (<0.1% error) and confirmed using a digital oscilloscope, wherein no theoretical conventional energy was possible. Materials characterizations included those that quantified any compositional change of the electrolyte by elemental analysis using ICPMS, XRF, and XRD, and SEM were performed on the anode. The electrical energies were continuously output over long-duration, measured on different systems, configurations, and modes of operation and were typically multiples of the electrical input that in most cases exceed the input by a factor of greater than 10. Calorimetry of solid fuels that exploited the same catalyst and a similar reaction mechanism showed excess thermal energy greater than 10 times the maximum possible from any conventional reaction. The predicted molecular hydrino H2(1/4) was identified as a product of CIHT cells and solid fuels by MAS 1H NMR, ToF-SIMS, ESI-ToFMS, electron-beam excitation emission spectroscopy, Raman spectroscopy, photoluminescence emission spectroscopy, FTIR, and XPS. Copyright © 2013 John Wiley & Sons, Ltd.

Transformation Process of the Magnetron-Sputtered Ag2O Film in Hydrogen Annealing

The current paper mainly addresses the effect of the hydrogen partial pressure on the microstructure and transformation of the Ag$_2$O film. The transformation process and mechanism were also analyzed in detail. Increasing the hydrogen partial pressure can accelerate the transformation of Ag$_2$O to Ag and lower the critical transformation temperature of the film due to the enhanced hydrogen reduction, and to both of the lowered activation energy of the reaction of Ag$_2$O with hydrogen and enhanced lattice strain of the Ag$_2$O film, respectively. Hydrogen-involved reaction in the whole hydrogen annealing process is mainly hydrogen reduction reaction with Ag$_2$O. The diffusion of hydrogen and gaseous H$_2$O molecules is accompanied with the whole hydrogen annealing process.

Corrosion Protection of Electro-Galvanized Steel by Ceria-Based Coatings: Effect of Polyethylene Glycol (PEG) Addition

A cerium oxide thin layer was deposited onto galvanized steel by cathodic electrodeposition from 0.1 M concentrated cerium nitrate solution. In this work, the influence of polyethylene glycol (PEG) addition on the composition and morphology of the deposits is examined. The results showed that the addition of PEG to the cerium nitrate solutions leads to a decrease in the cracks in the deposits by decreasing the hydrogen reduction reaction and by decreasing the film thickness which provided enhanced corrosion protection. Moreover, the substrate dissolution reaction is inhibited.

Effect of tensile stress in elastic and plastic range on hydrogen permeation of high-strength steel in sour environment

The new hydrogen permeation technique developed for the electrochemical permeation method makes it possible to evaluate the effect of applied tensile stress in both elastic and plastic range on hydrogen permeation behavior in high-strength steels. This study suggests that the iron sulfide film acts as sites for hydrogen reduction reaction and that the applied elastic stress weakens the stability of the sulfide film due to lots of cracks forming in the local sulfur deficient region, resulting in increase in both the anodic dissolution and hydrogen reduction reaction. In addition, the effect of applied stress in plastic range on hydrogen permeation behavior was clearly evaluated by excluding other side effects such as the reduced rate of hydrogen oxidation caused by the disruption of the Pd layer under stress. Furthermore, by evaluating hydrogen permeation behavior in the transient range from elastic to plastic stress, the effect of newly generated dislocation on the permeation current was accurately investigated without any side effect.

Carbon‐Supported Molybdenum Carbide Catalysts for the Conversion of Vegetable Oils

Ordered mesoporous carbon (OMC)-supported molybdenum carbide catalysts were successfully prepared in one pot using a solvent-evaporation-induced self-assembly strategy accompanied by a carbothermal hydrogen reduction reaction. Characterization with nitrogen sorption, small-angle XRD, and TEM confirmed that the obtained materials had high surface areas, large pore volumes, ordered mesoporous structures, narrow pore size distributions, and uniform dispersions of molybdenum carbide particles. With nitrogen replaced by hydrogen in the carbothermal reduction reaction, the formation temperature of molybdenum carbide could be reduced by more than 100 °C. By changing the amount of molybdenum precursor added from less than 2 % to more than 5 %, molybdenum carbide structures could be easily regulated from Mo(2) C to MoC. The catalytic performance of OMC-supported molybdenum carbide catalysts was evaluated by hydrodeoxygenation of vegetable oils. Compared with Mo(2)C, MoC exhibited high product selectivity and excellent resistance to leaching in the conversion of vegetable oils into diesel-like hydrocarbons.

Optical Nonlinearity of Mesoporous Silica Thin Films Embedded with Gold Nanoparticles

The mesoporous silica thin films (MSTFs) synthesized by evaporation-induced self-assembly were loaded with gold nanoparticles (GNPs). The TEM and XRD characterizations showed that the template of MSTF possessed a well-ordered mesostructure, and GNPs can be well crystallized in the thin film by neutralization and hydrogen-reduction reactions. The z-scan technique was used for studying the nonlinear optical properties of the GNPs/MSTF nanocomposite. The results showed that this kind of material was possessed of a relatively feeble nonlinear absorption but an obvious nonlinear refraction. The nonlinear refractive index was estimated to be 7.9 × 10−11 cm2/W and the theoretical fitting well matched with the measured data.

Developmental Mechanism for the Memory Effect in Perovskite Oxide-Based ReRAM Consisting of Bi2Sr2CaCu2O8+δ Bulk Single Crystal

Resistive random access memory (ReRAM) structures of M-TE/Bi2Sr2CaCu2O8+δ (Bi-2212) bulk single crystal/Pt-BE (M = Al, Pt) were prepared and their memory characteristics and superconducting properties were evaluated, here TE and BE represent top and bottom electrodes. The resistance switching effect developed only in the Al-TE/Bi-2212/Pt-BE structure and was enhanced with decreasing critical temperature by annealing in Ar atmosphere. This suggests that reduction of Bi-2212 single crystal is required for the resistance switching effect. Additionally, due to the large resistance anisotropy (ρc/ρab > 103) of bulk Bi-2212 single crystals, the resistance switching effect was confirmed to occur at the interface between the Al electrode and the Bi-2212 single crystal. These results indicate that introduction of an oxygen-depleted Bi-2212 layer to the surface of the Bi-2212 single crystal at the vicinity of the Al electrode is required to develop the resistance switching effect, which could be achieved by the deposition of electrodes with small Gibbs free energy and raising the temperature to exceed the activation energy for oxygen ions to move from the Bi-2212 single crystal to the electrode. A model which explains the resistance switching of perovskite oxide-based ReRAM by generation/recovery of the oxygen-depleted Bi-2212 layer. The most direct way to prove the validity of the proposed resistance switching model is to show the development of the resistance switching effect simply by inserting the oxygen-depleted Bi-2212 layer at the interface between a large Gibbs free energy electrode such as Pt and Bi-2212 single crystal. Utilizing the catalytic effect of Pt that drastically enhances the reduction reaction of hydrogen, we introduced the oxygen-depleted Bi-2212 layer into the surface of the Bi-2212 single crystal at the vicinity of the Pt electrode by annealing a Pt-TE/Bi-2212/Au-BE structure in H2 atmosphere. The resistance switching effect developed also in a Pt-TE/Bi-2212/Au-BE structure annealed in hydrogen gas, proving the validity of the resistance switching model.

Desenvolvimento e uso do compósito de Nb2O5|Cu como revestimento aplicado por aspersão térmica sobre o aço AISI 1020 para proteção contra a corrosão pelo solo em estruturas enterradas

An Nb2O|Cu corrosion-resistant coating was developed and applied onto AISI 1020 steel substrate by Powder Flame Spray. A galvanostatic electrochemical technique was employed, with and without ohmic drop, in four different soils (two corrosively aggressive and two less aggressive). Behavior of coatings in different soils was compared using a cathodic hydrogen reduction reaction (equilibrium potential, overvoltage and exchange current density) focusing on the effect of ohmic drop. Results allow recommendation of Nb2O5|Cu composite for use in buried structure protection.

AbstractsAstrobiology Graduate Conference (AbGradCon) 2011HOSTED BYMontana State UniversityBozeman, Montana • June 5–8, 2011

AbstractsAstrobiology Graduate Conference (AbGradCon) 2011HOSTED BYMontana State UniversityBozeman, Montana • June 5–8, 2011

Effect of heat treatment on oxygen storage capacity and oxygen release kinetics of alumina-supported ceria

The microstructural feature, oxygen storage capacity and hydrogen reduction reaction of alumina-supported ceria were examined to determine the activation energy of hydrogen consumption. The scanning and transmission electron microscopy under high magnification indicate the small agglomeration and the surface coverage of CeO2 on alumina. The activation energy E was 80–140 kJ/mol for reduction peaks at around 420 °C and 550 °C in the first reduction run. However, in the second run, E for the second peak changed depending on the CeO2 content. The results suggest the surface modification of CeO2 surface with alumina via heat treatment in both reducing and oxidizing atmosphere.

Preparation and characterization of membrane electrode assembly (MEA) for PEMFC

Fuel cell is a system that converts chemical energy to electrical energy from an oxidation–reduction reaction of hydrogen and oxygen. In this study, Pt/C catalyst, solvent, and a binder agent were mixed to prepare catalyst ink. First, we applied carbon black ink to the carbon paper to supply hydrophobic and hydrophilic structure on its surface, which is called as microporous layer (MPL). Then catalyst ink was deposited on the treated carbon paper to form gas diffusion layers (GDLs) for anode and cathode side of the fuel cell. At this position, catalyst layer surfaces and carbon paper were analyzed by using scanning electron microscopy (SEM) and it was seen by energy dispersive spectroscopy (EDS) analysis that the catalysts were spread uniformly on a carbon paper. A membrane is fixed between GDLs and hot-pressed at 120°C, 75 kg cm− 2 to compose membrane electrode assembly (MEA). In a fuel cell test unit, MEA has internal resistance, which was evaluated by applying current interrupt method and current–voltage curve was drawn by load application. As a result of the test, I-V curves were formed and compared with characteristic curve of commercial MEA. It was seen that the shapes of the curves are similar. Maximum power values are 100, 275, and 390 mW for homemade MEA without MPL, with MPL, and commercial MEA, respectively. MEA without MPL was susceptible to flooding, especially at high-currrent values. MPL is helpful to increase the porosity of the diffusion layer and this effect can improve the oxygen transfer rate and lead to a higher performance. Compared with commercial MEA, homemade MEA did not reach high-current and -power values due to lots of parameters which affects the fuel cell performance as catalyst activity, conditions of MEA preparation, and disorder of measurement conditions, etc. Copyright © 2010 John Wiley & Sons, Ltd.