Hi Jones, Sorry for the delay, here is the ref (note it refers to hydrogen, not deuterium, whose heat of adsorption could thus conceivably be the 2 eV per D found by Kitamura for 5 nm particle sizes):
"JOURNAL OF CATALYSIS 104, 1-16 (1987) Calorimetric Heat of Adsorption Measurements on Palladium I. Influence of Crystallite Size and Support on Hydrogen Adsorption PEN CHOU AND M. ALBERT VANNICE" Here is the abstract (some OCR errors may have escaped my scrutiny): << A modified differential scanning calorimeter was used to measure integral heats of adsorption of hydrogen, Qad, at 300 K on unsupported Pd powder and on Pd dispersed on SiO2, SiO2-Al2O3, Al2O3, and TiO2. The supports were found to have no significant effect on Qad, and although reduction of Pd/TiO2 samples at 773 K sharply decreased the amount of hydrogen chemisorbed on these samples, the Qad values measured on these samples were comparable to the other catalysts. In contrast, Pd crystallite size had a very pronounced effect on Qad. On all these catalysts the heat of adsorption for hydrogen remained constant at 15 +- 1 kcal mole^-1 as the average Pd crystallite size decreased from 1000 to 3 nm, but it increased sharply as the size dropped below 3 nm. The highest value, 24 kcal mole^-1, was obtained on one of the most highly dispersed samples. Heats of formation of bulk Pd hydride showed a similar behavior, remaining constant at 8.7 +- 1.0 kcal mole^-1 for samples with low Pd dispersions and then increasing noticeably as the crystallite size dropped below 3 nm. Most of this variation in Qad is attributed to changes in the electronic properties of small Pd crystallites because the differences in Qad values reported on single crystal surfaces are not sufficient to explain the enhanced bond strength.>> Michel 2009/12/30 Jones Beene <jone...@pacbell.net>: > Michel > > > > Ø The spread is not large for a given set of conditions. In particular > there is one very important (IMHO) point which seems consistently > overlooked, not just by you, which is that the binding energy is not the > same on the surface (heat of adsorption) as it is in the bulk (heat of > absorption). It's much higher on the surface. Interestingly, decreasing the > Pd particle size increases the surface binding energy (I can dig up a ref > if anyone is interested) which is what the Kitamura work re-discovers IMHO. > > > > By all means - we are very interested, since this is really one of the two > important points left to be decided. And providing this reference in an > unequivocal way (i.e. specifically wrt hydrogen and palladium) would salvage > your other comments out of the category of “fishy”. > > > > Therefore, we eagerly await your (hopefully authoritative) reference, since > the “much higher” surface binding attribute as you claim, is a bit > counter-intuitive; and without it we have a compelling set of circumstances > for expanding the importance of the putative anomaly – which as Terry > opined, might possibly be related to nascent hydrogen. > > > > The next issue, of course, is whether or not the 2 eV per atom loading heat > of Kitamura is accurate and reproducible by others. That is where I suspect > the problem will be found. > > > > Side note: as many of us are aware, hydrogen comes off of bulk palladium > easily enough that it can be, and once was, once used as a cigarette lighter > (which presumably did not require much input to ignite – other than a spark) > but was surely an expensive indulgence. > > > > As I recall – and a brief googling confirms, the so-called "Doebereiner > cigarette lighter" from the 1800’s was used by early CF skeptics to explain > away the excess heat of the P&F effect, since it apparently got quite hot > following a hydrogen recharge. > > > > Problem is – they apparently never checked the complete thermodynamic > balance of the Doebereiner effect … at least there is no record of that > which I can find. Is it presumptive to suggest, given Kitamura, that the > very same effect used by skeptics to try to disprove CF could instead point > to another, and perhaps more usable anomaly? > > > > Nah, probably not. But it would be one great way to convert palladium into > irony ;-) > > > > Jones > > > >
