Microcalorimetry of Electrochemical Reactions at Submonolayer Conversions

Abstract

We 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 100μm thin polycrystalline Au electrode. Pulsed electrochemical deposition or dissolution during 10ms 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.