Review of materials science for studying the Fleischmann and Pons effect

Fleischmann and Pons effect (FPE) is the production of excess power during electrochemical loading of deuterium in palladium. This effect has the following features: (1) It is a threshold effect (loading D/Pd > 0.9). (2) It is unobserved when electrochemical loading is performed with hydrogen from light water. (3) It is unexplainable as a chemical effect. (4) It occurs only if the involved materials have specific characteristics. The present article will review aspects concerning the occurrence of FPE related to materials science, a field considered to be a key to define the effect and a research approach has been conceived to find correlations with the material status. Metallurgy, crystallographic orientation and surface morphology all together are the necessary conditions to observe the phenomenon. In general, these features affect the deuterium adsorption/absorption in palladium cathodes. On the other hand, crystal orientation seems not to be crucial for PdRh alloy. A preliminary study, based on galvanostatic electrochemical impedance spectroscopy, has been carried out to investigate the status of the electrochemical interface during the effect. Results point in the direction of a significant change in the equivalent circuit at the electrode interface, as the electrode is active.