Microcalorimetry of Electrochemical Reactions at Submonolayer Conversions

Abstract

Electrochemistry / Calorimetry / Underpotential Deposition / Peltier Heat / Entropy of Electrode ReactionsWe measured heat effects upon underpotential deposition or dissolution of a fraction of a monolayer of Cu on a Au surface. Temperature changes due to electrochemical reactions were pyroelectrically detected at the backside of a 100 µm thin polycrystalline Au electrode. Pulsed electrochemical deposition or dissolution during 10 ms intervals prevented significant loss of heat into the electrolyte on that time scale. The combination of both, i.e., pulsed electrochemical reactions at a thin electrode with low heat capacity, leads to unprecedented sensitivity. In addition, we compare the experimental temperature transients with the temperature evolution simulated for our experimental setup. Interferences stemming from mechanical deformation of the electrode foil due to potential-induced surface stress are also discussed.

In-situ Thermoelectrochemistry

“…Commercially available thermistor probes in the form of small bulbs were protected by an insulating layer, and the working electrode wire was wound around the thermistor [331,332]. Instead of thermistors, pyroelectric foils carrying electrode layers have been used for calorimetry in situ [343][344][345][346][347]. Heat exchange of reactions of adhering solid crystals were determined by such arrangements.…”

“…Also, graphite hollow cylinders in close contact to a thermistor have been used [333,334]. Layers of nickel [343] and of platinum [344,345] have been studied, and the heat exchange even of a submonolayer conversion [346] has been determined. Thermistor probes covered by thick electrode layers of copper [335,336], silver [337] or platinum [338] proved also to be useful (Fig.…”

Heat Effects upon Electrochemical Copper Deposition on Polycrystalline Gold

“…We achieved the sensitivity to measure such minute heat effects by a combination of pyroelectric heat detection at the backside of a thin electrode and pulsed electrochemistry. [20,21] Experimental Section…”

“…[20,21]. In brief, the electrode temperature of a 12.5 mm thick polycrystalline Au foil, supported by a 120 mm thick Si sheet was measured at the backside of the electrode with a 9 mm thick pyroelectric Polyvinyliden (PVDF) foil.…”

Mikrokalorimetrische Messung des Lösungsmittelbeitrags zur Entropieänderung bei der elektrochemischen Lithiumvolumenabscheidung

“…Details zum Kalorimeter finden sich in Lit. [14,27]. Kurz zusammengefasst bestand das Kernstück des Kalorimeters aus einem 50 mm dicken Nickelblech, das in engem thermischem Kontakt mit einer goldbeschichteten Polyvinylidenfluorid(PVDF)-Folie stand, die als Temperatursensor fungierte.…”