A holistic approach on real-time analysis of degradation at solid-liquid interfaces

Abstract

Stability of electrified solid|liquid interfaces is decicive for a variety of electrochemical processes ranging from corrosion of structural materials to electrocatalysts. Electrochemical reactions, may they be desired as in catalysis or unintended as for corrosion inevitably lead to degradation of electrodes. Studying those inter- faces during electrochemical processes is challenging for classical, vaccum-based methods of surface science.In this thesis two complementary analytical methods are used to enable in situ tracking of the electrochemical processes taking place. Firstly, a electrochemical flow cell was developed, that, in combination with a down-stream analysis with inductively coupled plasma mass spectrometry (ICP-MS), enables a time and ele- mental resolved analysis of material degradation. Analysis of degradation products indirectly give an indication about composition of the degraded surface. Further, a novel design of an electrochemical cell for atomic force microscopy (AFM) comple- ments the knowledge gained with time-resolved topographies of an active electrochemical interface. Here local effects as roughening or delamination of the surface can be observed and therefore lead to a better understanding of the processes during dissolution.The influence of o-rings on corrosion studies in flow cells is shown exemplary for the corrosion of nickel-based alloys. Further the electrochemical passivation and qual- ity of the formed metal oxid layers on a series of metal alloys were studied in order to establish a material library to decipher the contributions of single alloying elements on the formation of a stable passive film. Also the flow cell was adapted for studying photoinduced corrosion of photoactiive semiconductors like zinc oxide.By this the variety of applications of the complementary methods of electrochemical ICP-MS flow cells and AFM for the investigation of electrified solid|liquid interfaces could be broadened. The developed analytical techniques supplement each other in their explanatory power and pave the way to gain complementary knowledge about fundamental processes on electrochemical active solid|liquid interfaces.