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Effect of Oxidation State of Palladium in Polyaniline Layers on Sensitivity to Hydrogen
Author(s) -
Josowicz Mira,
Li Hong Shi,
Domansky Karel,
Baer Donald R
Publication year - 1999
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/(sici)1521-4109(199907)11:10/11<774::aid-elan774>3.0.co;2-o
Subject(s) - polyaniline , palladium , hydrogen , x ray photoelectron spectroscopy , electrochemistry , materials science , aniline , amine gas treating , oxidation state , chemistry , analytical chemistry (journal) , chemical engineering , polymer , organic chemistry , metallurgy , composite material , electrode , catalysis , metal , engineering , polymerization
It is shown that the ratio of Pd 0 /Pd 2+ in polyaniline (PANI) has a major effect on the response of film to hydrogen. The palladium clusters were incorporated in PANI as the result of spontaneous reduction of PdSO 4 by electroactive PANI in the leucoemeraldine or nigraline form, respectively. The two forms of PANI were prepared, by terminating the electrochemical deposition at –0.1 V (PANI –0.1 V ) and by terminating it at +0.7 V (PANI 0.7 V ). A higher amount of Pd is incorporated in the in PANI when the reduction of Pd 2+ is initiated from the leucoemeraldine form. The ratio of the amine/imine units correlates well with the changes of the Pd 0 /Pd 2+ ratio as shown by the XPS. The changes of the work function were measured by a Kelvin Probe. A substantial decrease of WF was observed when the PANI –0.1 V ‐Pd composite film was exposed to hydrogen. On the other hand the WF of PANI 0.7 V ‐Pd film increases upon exposure to hydrogen. The change in the electron donor/electron acceptor behavior towards hydrogen is governed by the Pd 0 /Pd 2+ ratio in the PANI/Pd matrix.