Lakner, Pirmin H.Pirmin H.LaknerBrinker, ManuelManuelBrinkerSeitz, ChristophChristophSeitzJacobse, LeonLeonJacobseVonk, VedranVedranVonkLippmann, MilenaMilenaLippmannVolkov, S. A.S. A.VolkovHuber, PatrickPatrickHuberKeller, Thomas F.Thomas F.Keller2020-12-082020-12-082020-11-17Langmuir : the ACS journal of surfaces and colloids 45 (36): 13448-13456 (2020-11-17)http://hdl.handle.net/11420/8080This study reports on the potential-induced charge and mass transfer between an ultrathin polypyrrole (PPy) film and an electrolyte by simultaneous in situ X-ray reflectivity (XRR) and electrochemistry (EC) utilizing their sensitivity to electrons. An about 30 nm thin PPy film was deposited on a silicon single crystal by fast potential cycling, providing a dense film of an extraordinary small surface roughness. XRR was recorded from the PPy film in an aqueous 0.1 M perchloric acid at electric potentials between -0.2 V and +0.5 V vs Ag/AgCl. The PPy film shows typical reversible and linear changes in film thickness and electron density arising from the potential-dependent electrolyte incorporation. By introducing EC-XRR, a comprehensive analysis combining in situ XRR and EC, the net number of electrons passing through the PPy-electrolyte interface was deduced along with the potential-induced thickness variations, indicating a complex exchange mechanism. Evidently, along with the anion transfer, parallel charge compensation by protons and a volume and electron compensating counterflow of solvent molecules take place. Complementary time-dependent EC-XRR scans indicate that these exchange mechanisms are individual in two potential ranges. The low actuation along with a high pseudocapacitance suggest the fast potentiodynamically deposited PPy film as a promising supercapacitor material.en0743-74632020451344813456https://creativecommons.org/licenses/by-nc-nd/4.0/PhysikTechnikJournal Article10.15480/882.316110.1021/acs.langmuir.0c0206810.15480/882.316133151688Journal Article