PNNL

Abstract

It is shown that the ratio of Pd 0/Pd2+ 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 PdSO4 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 -0.1V) and by terminating it at +0.7 V (PANI 0.7V). A higher amount of Pd is incorporated in the in PANI when the eduction of Pd2+ is initiated from the leucoemeraldine form. The ratio of the amine/imine units correlates well with the changes of the Pd 0/Pd2+ 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 -0.1V -Pd composite film was composed to hydrogen. On the other hand the WF of PANI 0.7V-Pd film increases upon exposure to hydrogen. The change in the electron donor/electron acceptor behavior towards hydrogen is governed by the PANI/Pd matrix.