An empirical dependence of frequency in the oscillatory sorption of H2 and D2 in Pd on the first ionization potential of noble gases

Abstract

Oscillatory heat evolution in sorption of H(2) and D(2) in Pd can be induced by an admixture of ~10 vol.% of an inert gas (He, Ne, Ar, Kr, or N(2)) to either isotope prior to its contact with palladium powder. The oscillations are represented in the form of a calorimetric time series, recorded using a gas flow-through microcalorimeter at the temperatures of 75 °C for D(2) and 106 °C for H(2). For both D(2) and H(2), the oscillation parameters change as a function of the kind of inert gas used: the amplitude increases and the frequency decreases in passing from He to Kr. An empirical dependence of the oscillation frequencies observed for various admixtures and normalized with respect to Kr has been found. Accordingly, the frequency is a function of a product of the first ionization potential and the square root of atomic mass of the inert gas (He, Ne, Ar, Kr, or N(2)). On the other hand, invariance of the thermal effects of sorption is evident from the integrated areas under the calorimetric time series yielding the molar heats of sorption conserved, irrespective of the inert gas admixture. A novel calibration procedure has been devised in order to deal with an instability of calibration factor arising in desorption of H(2) and D(2) from Pd. A method of dynamic calibration factor made it possible to obtain a good agreement between the heats of sorption and desorption of both H(2) and D(2) within individual sorption-desorption cycles for all inert gas admixtures.

Humidity induced deactivation of Al2O3 and SiO2 supported Pd, Pt, Pd-Pt catalysts in H2+O2 recombination reaction: The catalytic, microcalorimetric and DFT studies

“…Error estimation for the microcalorimetric measurements has been attempted in ref. [21] basing on a collection of 50 sorption/desorption cycles of hydrogen in metallic palladium powder. The data has been represented as a function of H 2 partial pressure, separately for the heats of sorption and desorption.…”

Chaos in oscillatory sorption of hydrogen in palladium

“…This thermal effect turns out to be slightly below the average amount of heat recorded on reaching saturation for this Pd sample (ca. 0.09 kJ/g Pd) under the same conditions [2]. Hence, at the point of 4,000 s the Pd sample must be rather close to the state of saturation with deuterium.…”

“…The experimental procedure leading to periodic or quasiperiodic oscillatory sorption of H 2 (D 2 ) in Pd has been recently described in detail in Ref. [1,2]. The oscillatory kinetics begins with a fresh Pd powder and, after a 20-30 min, the oscillations cease (in most cases) when the Pd sample is saturated (cf.…”

“…Oscillatory heat evolution accompanying the sorption of hydrogen or deuterium in metallic palladium has recently been described in two reports [1,2]. The thermokinetic oscillations can been induced by admixing hydrogen or deuterium with ca.…”

“…Niezapominajek, 30-239 Kraków, Poland e-mail: nclalik@cyf-kr.edu.pl of an inert gas, such as He, Ne, Ar, Kr or N 2 , prior to its contact with palladium. The frequencies turned out to be functionally dependent on the atomic parameters (the first ionization potential and the square root of atomic mass) of the inert gases being used in the reaction [2]. Apart from specifying conditions for the oscillatory kinetics to occur, the calorimetric experiments have also demonstrated a consistent invariance of the value of the heat of sorption of H 2 (D 2 ) in Pd, which remains the same over a whole range of frequencies observed, independent of whether the oscillations are periodic or quasiperiodic, and irrespective of the process duration.…”