Phenomenological Interpretation of the Multistep Thermal Decomposition of Silver Carbonate To Form Silver Metal

Thermal decomposition of Ag2CO3 to form Ag occurs via a multistep reaction, and the reaction pathway varies drastically with the sample and reaction conditions. Understanding this complex reaction behavior has significance today with respect to the formation of Ag nanoparticles via the thermal decomposition of Ag compounds. In this study, the thermal decomposition of three different Ag2CO3 samples that exhibited different reactivities and reaction pathways was investigated via thermal analyses under linearly increasing temperatures and by studying the morphology of the reacting particles. The thermal decomposition was kinetically deconvoluted into four or five partially overlapping reaction steps, in which the contributions of each reaction step to the overall thermal decomposition of Ag2CO3 to Ag varied as a function of the properties of the sample particles and the heating rate. This complex reaction behavior resulted from the competitive interaction of two physicochemical processes, i.e., sintering of the product particles in the surface product layer and the diffusional removal of the generated gases, during the thermal decomposition of Ag2CO3 and the intermediate compound Ag2O in the geometrical reaction scheme for a contracting volume induced by surface reactions. The high sintering ability of the Ag2O and Ag formed in the surface product layer causes the complex reaction behaviors during the thermal decomposition and disturbs the formation of Ag nanoparticles.