PreviousLy, chemical oxidation of TlCu3X2 (X= S,Se) as a powder immersed in ammonia solution effectuated a phase transformation into the p-metal TlCu2X2. In order to explore whether the small grain size and intimate contact with the liquid phase were imperative, we introduce an electrochemical method with the starting phase as a polished rotating electrode.---The microstructures of polished electrode surfaces indicate that processes within the solid rather than in the interface with the electrolyte are important. The slower and less efficient reduction process may be explained from topotactic symmetry considerations.