Steven Crouch-Baker

Isothermal flow calorimetric investigations of the D/Pd and H/Pd systems

Abstract Isothermal calorimetric studies of the D/Pd and H/Pd systems have been carried out at high deuterium (hydrogen) loadings (i.e. [D(H)]/[Pd] > 0.9) at approximately 30°C. Under these conditions, the generation of “excess power” was observed in a series of deuterium-based experiments, but not in a hydrogen-based experiment. The results of these experiments enable several (tentative) conclusions to be reached concerning the conditions necessary for the reproducible observation of this anomalous thermal effect.

The effect of ultrasound on the electrochemical loading of hydrogen in palladium

Although the application of ultrasound for the control and modulation of various chemical processes is a subject of continued interest [l], there is surprisingly little discus- sion in the recent literature of the effects of ultrasound on fundamental electrochemical processes. In early systematic studies of the hydrogen evolution reaction under acidic conditions [2,3], it was observed that, on a platinum elec- trode, the overvoltage for hydrogen evolution decreased by up to 30mV on the application of ultrasound, and that this decrease was largely independent of current density in the approximate range l-100 mA cm-‘, i.e. the Tafel slope was largely unaffected under these conditions. On removal of the ultrasound, the original polarization was regained only on continued electrolysis for up to 1 h. These results refer to electrolytes which had been pre-electrolysed for 10 to 20h. With more extensive pre-electrolysis (36h), the results were generally similar; however, the polarization decrease on the application of ultrasound was smaller (by a factor of two) under comparable conditions, and the origi- nal polarization was recovered rapidly on cessation of irradiation. On the application of ultrasound to a nickel electrode evolving hydrogen, the same general phe- nomenon was observed, i.e. a decrease in overvoltage without a significant change in Tafel slope [3]. For these experiments, the acoustic frequency was 3OOkHz and the ;icoustic intensity was estimated to be approximately I Wcmw2 of electrode area.