Micropatterning of Metals by Tip Electrode Dissolution and Imaging of Oxygen Reduction Reaction Using Scanning Electrochemical Microscopy

Abstract

Surface patterning on substrate has been applied to various nano-devices, microfluidics, cell biology, microelectrochemical systems, and electronics. Most strategies have been based on lithography, but despite the many advantages of conventional lithography, its complex procedures, facilities and high cost arouse desire for the alternative technique. The major complexity in lithography is due to the indirect patterning which uses mask as a template and results in multi-step process. Meanwhile, electrochemical patternings have been also carried out for patterning of metals, and especially maskless patternings are possible using scanning electrochemical microscopy (SECM). We have electrodeposited palladium and gold micropatternings using SECM with the metal precursor ions generated via anodic dissolution of the ultramicroelectrode (UME) tip itself. Simultaneously, in‐situ reduction of the metal ions occurred at the substrate electrode. Contrary to general electrodeposition methods where metal precursor ions exist in the entire solution, in case of local deposition, the metal ions were supplied only from the anodic dissolution of the tip electrode composed of the identical metal which was positioned in a close proximity to the substrate. Therefore, the ions generated from the tip can be reduced only on nearby substrate, not on the entire conductive surface. Especially, this is the first study on the local deposition of Pd using direct Pd dissolution. The catalytic activities of oxygen reduction on the Pd or Au patterns were investigated simultaneously but separately with tip generation‐substrate collection mode of SECM and the activities of each metal deposit varied with potentials applied on substrate. This local deposition technique using SECM could be also applied to other metals if the metal dissolution is possible in proper electrolyte solution within water-stable potential window. Figure 1