The kinetics of silver electrodeposition from sulfite solutions

Silver electrodeposition from sulfite electrolytes is considered to be one of the most promising processes to replace the extremely toxic traditional cyanide-based silver plating solutions with the additional advantage, that sulfite electrolytes can be successfully applied for silver deposition for micro-electro-mechanical systems (MEMSs). Mechanism of metal complexes electroreduction is an important result, especially when it may have a wide range of applications in the future. However, electrodeposition also has several shortcomings, including sulfite ion oxidation by oxygen in air and relatively negligible cathodic current densities, which are too low for qualitative galvanotechnique. There are very few works dedicated to the chemistry and electrochemistry of silver sulfite complexes. Most publications related with this subject are concerned with the questions of applicability. The main objective of this study was the investigation of the silver sulfite complexes electroreduction kinetics. To achieve this goal, we studied the dependence of the exchange current density on the free sulfite ions concentration in a series of isopotential solutions. Our studies also allowed to determine the mechanism of this electrochemical charge transfer reaction