Dynamics of the Galvanic Replacement Reaction of Silver by Gold: Phenomenological Models for Open Circuit Potential‐Time Responsive Indicator

Galvanic replacement reaction (GRR) is an oxidation–reduction process triggered by an electrochemical potential difference between two metal species, and involves the concerted motion of electrons, atoms, and ions at different times and spatial scales. Despite extensive research, a fundamental question remains unanswered: How can the driving force, that is, the electrochemical potential, be mapped in real time when existing microscopic, optical, and X‐ray methods cannot capture it? In this article, the most widely used and fascinating system: silver‐gold, in which three silver atoms are replaced by one gold atom, despite silver and gold having almost identical atomic radii, is interrogated. The experimental time‐dependent open‐circuit potential (OCP( t )) data, as well as phenomenological and mathematical models, are leveraged to describe the dynamics of the GRR. Specifically, modified sigmoidal kinetic functions are proposed based on autocatalytic networks and enzyme cascades performing logic gates, in order to account for the offset and sharpness of the OCP( t ) responses at different input concentrations. This allows quantifying, for the first time, the two highly sought‐after kinetic parameters of the apparent rate constant and the midpoint growth time. This knowledge can inspire new explorations in GRR‐derived syntheses involving different galvanic exchange ratios for new functional nanostructured materials.