Mechanism of Heat Generation from Loading Gaseous Hydrogen Isotopes into Palladium Nanoparticles

Olga Dmitriyeva,, University of Colorado at Boulder

Abstract

I have carried out the study of hydrogen isotope reactions in the presence of palladium nanoparticles impregnated into oxide powder. My goal was to explain the mechanisms of heat generation in those systems as a result of exposure to deuterium gas. Some researchers have associated this heating with a nuclear reaction in the Pd lattice. While some earlier experiments showed a correlation between the generation of excess heat and helium production as possible evidence of a nuclear reaction, the results of that research have not been replicated by the other groups and the search for radiation was unsuccessful. Therefore, the unknown origin of the excess heat produced by these systems is of great interest.

I synthesized different types of Pd and Pt-impregnated oxide samples similar to those used by other research groups. I used different characterization techniques to confirm that the fabrication method I used is capable of producing Pd nanoparticles on the surface of alumina support. I used a custom built gas-loading system to pressurize the material with hydrogen and deuterium gas while measuring heat output as a result of these pressurizations. My initial study confirmed the excess heat generation in the presence of deuterium. However, the in-situ radiometry and alpha-particle measurements did not show any abnormal increase in counts above the background level. In the absence of nuclear reaction products, I decided to look for a conventional chemical process that could account for the excess heat generation.

It was earlier suggested that Pd in its nanoparticle form catalyzes hydrogen/deuterium (H/D) exchange reactions in the material. To prove the chemical nature of the observed phenomena I demonstrated that the reaction can be either exo- or endothermic based on the water isotope trapped in the material and the type of gas provided to the system. The H/D exchange was confirmed by RGA, NMR and FTIR analysis. I quantified the amount of energy that can be released due to the H/D exchange and proved that the heat generated during the experiments can be fully accounted for by this chemical reaction. Based on these results I concluded that the origin of the excess heat generated during deuterium loading of Pd-nanoparticle materials is chemical rather than nuclear.

I also looked at which measurement artifacts can result in apparent heat generation. I suggested that the presence of a thermal gradient within the system can alter the temperature measurement baseline, which would then look like anomalous heating under gas pressure. To test the hypothesis I experimentally enhanced thermal gradients in the gas-loading system and successfully demonstrated the effect. By using a commercially available finite element solver I matched experimental and simulated data to quantify the magnitude of the thermal gradient required to produce a measurable effect. Based on my observations I proposed a technique that would ensure the proper gas-loading system calibration and help to avoid any misinterpretation of the results.