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The Palladium-Hydrogen System
Abstract
Attempts to confirm Fleischmann and Pons's observations of cold fusion phenomena have met with inconsistent results. This second workshop on this topic brought together skeptics and advocates to facilitate communication, to examine closely the experimental results, and to identify research issues. BACKGROUND The majority of attempts to confirm cold fusion phenomena have been unsuccessful. Although some researchers have confirmed portions of the Fleischmann and Pons experiment, these results have been sporadic and difficult to reproduce. The first workshop on this topic, sponsored by the Department of Energy, was held in May 1989 in Santa Fe, New Mexico.
... Since Graham first observed in 1866 that huge amounts of hydrogen could be stored into a palladium rod, the palladium-hydrogen system has been the subject of many studies 177,178 and reviews 179,180 . The palladium-hydrogen system has been widely used as a model system to understand the sorption processes and because it represents a classic example of the removal of gas from a binary solid phase. ...
... However the isotherms do not show the hysteretic difference in the hydrogen pressure exists between the → and the → phase transition 179 . When the hydrogen content is increased (absorption isotherm), the pressure measured shows a greater value than when the hydrogen content is being removed (desorption isotherm), shown in Figure 1.3. ...
... A hysteresis scan is also shown starting from the decomposition plateau. Taken from179 . ...
The detection of local variations of the proton activity is of interest in many fields such as corrosion, sedimentology, biology and electrochemistry. Using nanostructured palladium microelectrodes Imokawa et al. fabricated for the first time a reliable and miniaturized sensor with high accuracy and reproducibility of the potentiometric-pH response. In absence of oxygen, the nanostructured palladium hydride tips are sensitive only to the activity of the protons close to their local environment and they have an almost Nernstian theoretical response with a slope of -58.7 mV/pH (25C) from pH 2 to 14. In the bulk, the lifetime of the palladium hydride sensor is 60 times longer when the solution is saturated with argon than with oxygen. Besides, the open circuit potential (OCP) recorded during the discharge of the hydride is more positive in an oxygenated solution. To unravel the influence of oxygen on the potentiometric response of these tips, we carried out a series of potentiometric and amperometric scanning electrochemical microscopy (SECM) experiments over a range of tip-substrate distances against an inert substrate. Potentiometric SECM experiments in aerated solutions demonstrate that the duration of the hydrogen discharge and tip potential depend on the tip-substrate distance: the closer the tip is to an inert substrate, the longer the lifetime of the sensor is, and the more cathodic the open circuit potentials are. Linear sweep voltammetry (LSV) near the OCP values reveals that the polarization resistance decreases when the tip approaches the substrate. These trends are confirmed by Tafel plots recorded over a range of tip-substrate distances. Potentiometric and amperometric measurements are found to be in good agreement. These results can be analysed in terms of a mixed potential theory as used in corrosion. They reveal that in the potentiometric mode, despite being held at zero current, the tips promote the reduction of oxygen which in turns leads to the rapid discharge of hydrogen from the palladium hydride. The closer the tip is to the substrate, the smaller is the flux of oxygen, the longer is the duration of the discharge and the more negative is the OCP. This dissertation will therefore show that even in a potentiometric SECM experiment where the tip is supposed to be a passive probe, hindered diffusion can affect the tip potential and produce a dependence on the tip-substrate distance. In aerated solutions, a simple correction can be made to bulk experiments. In this study the exceptional potentiometric properties of pH microprobes made with nanostructured palladium hydride microelectrodes are reported to demonstrate their application by monitoring pH variations resulting from a reaction confined in a porous medium. Their properties were validated by detecting pH transients during the carbonation of Ca(OH)<sub>2</sub> within a fibrous mesh. Experimental pHs recorded in situ were in excellent agreement with theoretical calculations for the CO2 partial pressures considered. Results also showed that the electrodes were sufficiently sensitive to differentiate between the formation of vaterite and calcite, two polymorphs of CaCO<sub>3</sub>. These nanostructured microelectrodes are uniquely suited to the determination of pH in highly alkaline solutions, particularly those arising from interfacial reactions at solid and porous surfaces.
... The lattice constant becomes a is 0.404nm. A volume expansion of 11.7% has been shown while transitioning from the alpha to beta phase [17]. ...
... In material science, this means that there is a stretch or expansion in a material and studies have shown than in the β-phase, there is strain. Because hydrogen pressure needs to be higher for the absorption of hydrogen at the same temperature than for adsorption, an irreversible plastic deformation with loss of heat between the cycles has been observed [17]. ...
In this project, a sensor-based leak detection monitoring system of hydrogen will be developed. The topic’s main purpose is to increase hydrogen’s safety and ensure safe transportation of units carrying all states of hydrogen. This can be done using a Palladium based sensor, which will be the focus of this report. Through understanding the behavior and the principle working of palladium, we were able to choose a design and compute a simple mathematical model for hydrogen detection by the sensor. Additional sensors will be added for the enhancement of the Pd-Hydrogen sensor.
... As a hydrogen adsorbent, the Pd depends on the increased resistance obtained in the process of hydrogen dissolution into the metal, resulting in the Pd hydride showing lower conductivity than the pure Pd [299]. Hydrogen ions are small enough to diffuse in the Pd lattice, causing an effective change in the lattice volume [300]. The Pd particles close the pores of the host material; hence the total volumetric output of molecular hydrogen at room temperature limits the growth of Pd content [237]. ...
Sustainable development of hydrogen energy is a prime concern to address the rising energy demand and the global energy problem since the hydrogen economy is reliable for clean and carbon-free energy carriers. Despite well-established commercial sector technologies, boil-off losses, explosive nature, and leakage risk still exist with compressed and liquefied storage. One of the significant remedies, solid-state hydrogen storage, improves bulk density and gravimetric capacity and addresses safety concerns. The rising popularity of light and heavy fuel cell vehicles is projected to promote the advancement of onboard solid-state hydrogen technology. The present review focuses on the importance of existing porous materials, polymers, metal, and complex metal hydrides for solid-state hydrogen storage and the dominance of Si nanostructures (SiNSs). The fabrication techniques of porous silicon, porous silicon nanowires, and Si quantum dots are accentuated. The review provides insights into the hydrogen-assisted properties, regularities, the importance of hydrogen energy on automobiles for alleviating climate change phenomena, and the application of SiNSs for hydrogen storage with other transition and alkali earth materials to overcome the issues. It highlights the importance of catalysts in resolving the existing reversibility and desorption issues associated with hydrogen energy storage. Different popular desorption techniques considering the pore dimensions are discussed. The evaluation may enable energy providers and Si-based fuel cells to be better customized, promoting the development of the hydrogen energy economy.
Hydrogen storage and production via electrochemistry using advanced amorphous metal catalysts with enhanced performance, cost, and durability may offer dynamic and intermittent power generation opportunities. As a new sub-class of materials, Pd-based metallic-glasses (MGs) have drawn intense attention because of their grain-free, randomly packed atomic structure with intrinsic chemical heterogeneity, bestowing unique physical, structural, and chemical properties for energy applications. Wee first give a general introduction to Pd and Pd-based MGs, including the fabrication techniques of MGs and their hydrogen applications. We then cover hydrogen sorption of Pd-based MGs examined under ribbons, nanowires/microrods, and thin-films subsections. Hydrogen evolution via Pd-based MGs is then analyzed under the bulk rod, ribbons, and thin-films subsections and hydrogenation kinetics and sensing, pseudocapacitance, and electron transfer kinetics subsections are discussed. Finally, a broad summary of Pd-based metallic glasses and future prospects. Altogether, this review provides a thorough and inspirational overview of hydrogen sorption and evolution of Pd-based MGs targeted for future large-scale hydrogen energy storage and production systems.
In situ gas-loading sample holders for two-dimensionally arranged detectors in time-of-flight neutron total scattering experiments have been developed to investigate atomic arrangements during deuterium absorption using time and real-space resolution. A single-crystal sapphire container was developed that allows conditions of 473 K and 10 MPa hydrogen gas pressure. High-resolution transient measurements detected deuterium absorption by palladium that proceeded within a few seconds. A double-layered container with thick- and thin-walled vanadium allowed conditions of 423 K and 10 MPa hydrogen gas pressure. The deuterium occupation sites of a lanthanum–nickel–aluminium alloy are discussed in detail on the basis of real-space high-resolution data obtained from in situ neutron scattering measurements and reverse Monte Carlo structural modeling.
Hydrogen isotope separation can be achieved using a palladium (Pd) membrane because protium (H) and deuterium (D) exhibit different solubility, diffusivity and, hence, mixed-gas permeability in Pd. The permeability of H (kH2) and D (kD2) were evaluated using a 4 vol% D2 – 96 vol% H2 feed mixture at temperatures of 293 K–473 K and pressures of 239 kPa–446 kPa in a continuous Pd membrane separation unit. The Pd foil membrane (0.1 mm thick) is shown to be selective toward H2 over the entire temperature range, with both kH2 and kD2 increasing with temperature. As temperature increases, the mixed-gas selectivity (kH2/kD2) rises from 4.0 at 300 K to a maximum value of 9.6 in the 363 K–373 K temperature range (which represents the operating temperatures that would render the highest concentration of H2 in the permeate and the greatest concentration of D2 in the retentate), then decreases to 6.2 at 480 K. Competitive transport during co-permeation is a likely cause for the maximum separation factor kH2/kD2 observed in this temperature range, being larger than the values predicted using pure gases (2 for diffusion dominant separation). The membrane selectivity presumably decreases from the observed maximum because the reverse solubility isotope effect decreases as the temperature increases. Additionally, isotope diffusion begins to increasingly affect the selectivity at higher temperatures.
Extensive use of palladium in many catalysts and catalytic converters causes a high degree of pollution of water and soil resources. Therefore, there is an urgent need to develop rapid and sensitive palladium probes. Herein, a novel “turn-on” near-infrared (NIR) fluorescence and colorimetric probe for Pd has been designed on the basis of the deallylation of the probe, followed by the release of NIR emissive fluorophore through the Tsuji-Trost reaction. The probe can selectively discriminate between the oxidation states of Pd⁰ and Pd²⁺. Sensing results demonstrates that the probe has excellent selectivity, sensitivity, fast response time, NIR fluorescence, high biocompatibility, and low detection limit for the Pd detection over a series metal ion. The probe has been successfully applied in visualization of residual Pd content from water, soil, drug and living cell samples by fluorescence observation with the naked eye.
The structure–activity relationship is a cornerstone topic in catalysis, which lays the foundation for the design and functionalization of catalytic materials. Of particular interest is the catalysis of the hydrogen evolution reaction (HER) by palladium (Pd), which is envisioned to play a major role in realizing a hydrogen‐based economy. Interestingly, experimentalists observed excess heat generation in such systems, which became known as the debated “cold fusion” phenomenon. Despite the considerable attention on this report, more fundamental knowledge, such as the impact of the formation of bulk Pd hydrides on the nature of active sites and the HER activity, remains largely unexplored. In this work, classical electrochemical experiments performed on model Pd(hkl) surfaces, “noise” electrochemical scanning tunneling microscopy (n‐EC‐STM), and density functional theory are combined to elucidate the nature of active sites for the HER. Results reveal an activity trend following Pd(111) > Pd(110) > Pd(100) and that the formation of subsurface hydride layers causes morphological changes and strain, which affect the HER activity and the nature of active sites. These findings provide significant insights into the role of subsurface hydride formation on the structure–activity relations toward the design of efficient Pd‐based nanocatalysts for the HER. Using a combination of experimental and theoretical approaches, the structure–activity relations that govern the complex electrochemical processes for the hydrogen evolution reaction (HER) on Pd electrodes is reported. The formation of subsurface hydride results in morphological changes, inducing a strain, which affects the activity toward the HER.
Hydrogen is regarded as the ultimate fuel and energy carrier with a high theoretical energy density and universality of sourcing. However, hydrogen is easy to leak and has a wide flammability range in air. For safely handling hydrogen, robust sensors are in high demand. Plasmonic hydrogen sensors (PHS) are attracting growing interest due to the advantages of high sensitivity, fast response speed, miniaturization, and high‐degree of integration, etc. In this review, the mechanism and recent development (mainly after the year 2015) of hydrogen sensors based on plasmonic nanostructures are presented. The working principle of PHS is introduced. The sensing properties and the effects of resonance mode, configuration, material, and structure of the plasmonic nanostructures on the sensing performances are discussed. The merit and demerit of different types of plasmonic nanostructures are summarized and potential development directions are proposed. The aim of this review is not only to clarify the current strategies for PHS, but also to give a comprehensive understanding of the working principle of PHS, which may inspire more ingenious designs and execution of plasmonics for advanced hydrogen sensors. Hydrogen sensors based on plasmonic nanostructures with their plasmonic effect, metal‐hydrogen interaction, working principle, and sensing properties are introduced in this review. The merit and demerit of different types of plasmonic nanostructures are summarized and potential development directions are proposed, aiming to inspire more ingenious designs and execution of plasmonics for advanced hydrogen sensors.
The mechanism proposed by Oppenheimer and Phillips for the disintegration of nuclei by deuterons with proton emission (d−p reaction) is examined. A formula is derived which expresses the probability of this process in terms of the sticking probability of the neutron (§2) and the penetrability of the potential barrier. The importance of the finite (rather than zero) nuclear radius for the penetrability is pointed out and the penetrability is calculated for various values of the radius (§3). The energy distribution of the emitted protons is found to be given directly by the sticking probability of the neutron (§5). Therefore it may differ considerably from the distribution in "ordinary" nuclear reactions by containing relatively more high energy protons. A measurement of the energy distribution would allow direct conclusions about the width of low nuclear levels which is of importance for the theory of the α-decay and therefore of the nuclear radius (§5). The probability of the O-P reaction is compared with that of ordinary nuclear reactions. The O-P mechanism is found to prevail in the d−p reactions for nuclear charges of about 25 and higher; if the reaction leads to a nucleus which emits fast β-rays, the O-P mechanism will be valid at still lower charges. The relative probability of d−p as compared to d−n reactions is found to be (on the average) unity for very light nuclei, to decrease with increasing atomic number until the O-P process becomes prevalent, and to increase from there on. The excitation function of reactions with nuclei up to Z∼30 is found to be an inadequate test for the O-P mechanism (§6). The question of secondary (cascade) disintegration following the d−p reaction is discussed and it is found that such disintegrations (e.g. d−pn or d−pα) should be rare with deuteron energies below the top of the potential barrier (§7).
A synergistic quasi-free electron laser for generating infrared radiation. The laser includes a means for producing a volume of ionized gas plasma, a means for directing an electron beam through the gas plasma in a first direction, and a means for directing a laser pump beam into the gas plasma in a second direction opposite to the first direction to produce synergistic bunching of the electron beam and the ionized gas plasma. A portion of the laser pump beam is backscattered by the bunched electron beam and gas plasma to form an output beam having a frequency up-shifted from that of the laser pump beam. The frequency of the output beam may be tuned by charging the velocity of the electron beam.
We have developed a spectrometer for MeV neutrons that relies upon total energy absorption to measure neutron energy. A coincidence signal is required from the capture of thermalized neutrons in Li-6 glass scintillators incorporated in the detector body. This dual signal from a single neutron provides a powerful means of discrimination against background events arising either from gamma rays or from ambient, low-energy neutrons. The spectrometer is particularly useful in situations in which the neutron source intensity is very low.
During solar particle events from 1968 to 1971 we observed increases in
the fast neutron flux at high latitude and at 55- to 75-g/cm²
atmospheric depth. The increases correlated with the variations in the
solar proton fluxes; the neutron yield per incident proton, above
threshold, increased by a factor of 100 with increasing hardness of the
proton spectrum. Within a factor of 2 the neutron specific yield fell on
a smooth curve versus the spectral parameter P0, where the
values of P0 were based on the SPME (solar proton monitor
experiment) data from Explorer 34 and 41. The neutron yield from solar
particle events was calculated from a Monte Carlo simulation of neutron
production and transport in the atmosphere. We compare the observed fast
neutron flux with that calculated using the solar proton spectra
reported at the times of the measurements; the causes for variation
among the reported proton spectra and between the calculated and the
observed fast neutron flux are discussed. The calculation reproduced the
results of experiments by others with moderated slow neutron counters in
and above the atmosphere. We calculate that the contribution of solar
particle fluxes to the production rates of neutrons, to the production
rates of radiocarbon, and to the leakage rates of neutrons from the top
of the atmosphere are 2-3 orders of magnitude below the galactic
cosmic ray contribution during solar cycle 20.
Solubility enhancements have been observed for hydrogen in thin Pd films (250–820 Å) in the αphase. Thermodynamic data for the films are determined from isotherms at temperatures between 25 and –40 °C and are compared with those for bulk Pd. From the values of WH—H(interaction energy of hydrogen in the film) and the solvus behaviour, it is suggested that the hydride phase in the films is destabilized relative to the dilute phase as the film thickness decreases. The dependence of the solubility on annealing has been examined for a thin film. The results indicate that the special characteristics of thin films disappear after annealing at ca. 400 °C.
This paper reports how D+ was compressed galvanostatically into sheet, rod and cube samples of Pd from 0.1 M LiOD in 99.5% D2O+0.5% H2O solutions. Experiments of several kinds were performed: (1) calorimetric measurements of heat balances at low current densities; (2) calorimetric measurements at high current densities; (3) determination of γ-rays emitted from the water both, as well as that of the neutron flux; and (4) determination of the generation/accumulation of tritium. It was found that enthalpy generation can exceed 10 W cm-3 of the palladium electrode; this is maintained for experiment times in excess of 120 h, during which typical heat in excess of 4 MJ cm-3 of electrode volume was liberated. The authors believe it inconceivable that this could be due to anything but nuclear processes.
A FEW months ago, K. Peters and I published an account of experiments we had made in an attempt to transmute hydrogen into helium (Ber. d. Deutschen Chem. Ges., 59, 2039; 1926). A more or less detailed account of this publication appeared in the columns of NATURE (vol. 118, p. 526, 1926), and perhaps I may be permitted to refer to a more recent publication on the same topic by K. Peters, P. Günther, and myself (Ber. d. Deutschen Chem. Ges., 60, 808; 1927). In this communication, as a result of further experiments, we feel that we are in a position to give an explanation of the occurrence of the observed very small quantities of helium in our experiments, without having recourse to the assumption of a synthesis of helium.
A model of deuterium-deuterium (D-D) fusion in metal lattices is presented based on two phenomena: reactions between virtual-state pairs of deuterons bound by electrons of high effective mass m and deuterium energy upscattering by fast ions from fusion or tritium reactions with virtual-state nuclear structure groups in palladium nuclei. Since m is a decreasing function of deuterium ion bulk density nâ the exponential barrier tunneling factor decreases rapidly with m. As a result, the fusion rate reaches a maximum at a loading density above zero but less than saturation. This can explain observations of transient neutron output from the (³He,n) branch, of D-D fusion.