Concentration mapping around copper microelectrodes studied by scanning electrochemical microscopy

The dendrite formation in a galvanic cell formed by two neighboring-copper-sources microdisc electrodes was investigated in concentrated oxalic acid solution. With simultaneous local-electrochemical measurements such as scanning electrochemical microscopy (SECM) imaging in feedback and substrate generator/tip collector modes, coupled with the electrolyte resistance imaging, both the local concentration of copper complexes and the surface modification around the two copper microelectrodes were monitored. The electrolyte resistance imaging allowed the formation of an electrical contact to be evidenced between the two copper microelectrodes due to the dissolution of one of the two electrodes and to the deposit of copper on the second one. Simultaneously, the SECM tip evidenced the consumption of the dissolved copper ions between the two microdisc copper electrodes, which indicate a copper deposition. This was also confirmed by SEM observations.