NMR comparisons of nanocrystalline and coarse-grained palladium hydride and deuteride.
Two distinct proton NMR lines were previously reported in nanocrystalline PdH{sub x} (r=5nm, x=0.70), and were tentatively assigned to H in the crystalline cores and in grain boundaries. Here we show this assignment to be incorrect, with all of the H in the Pd forming a single line and the second line arising from surface-bound H{sub 2}O formed by reaction with an initial oxygen surface layer on the Pd. Distinct spectroscopic signatures of deuterium in boundaries and in crystalline cores are sought in the rigid lattice {sup 2}D spectrum of nano-PdD{sub x} and in the onset of motional narrowing. In neither case is two-part behavior found; the results are nearly identical to those in coarse-grained PdD{sub x}. The spin-lattice relaxation rate R{sub 1} of {sup 2}D in nano-PdD{sub x} is compared to that in coarse-grained material. The electronic (Korringa) contribution, dominant below 125 K, is 1.58 times as large in nano-PdD{sub x}, indicating a substantial difference in the electronic structure in the boundary regions of nano-PdD{sub x}. Above 200 K, a contribution to R{sub 1} from exchange with D{sub 2} gas and/or surface adsorbed species is observed for nano-PdD{sub x}, a result of the large surface area.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Science Foundation (NSF)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 961182
- Report Number(s):
- ANL/MSD/JA-45298; TRN: US201010%%1001
- Journal Information:
- Phys. Rev. B, Vol. 67, Issue 5 ; Feb. 1, 2003; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
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