A new microcell or microreactor for material surface investigations at large current densities

Abstract The capillary-based droplet cell is well established in microelectrochemical surface analysis down to the μm range. The potentiostatic 3-electrode arrangement allows all common techniques like cyclovoltammetry, impedance spectroscopy and current transients of potential steps. A limiting factor was the immobile electrolyte, which meant an accumulation of products or depletion of educts, especially at larger current densities. Reaction products like gases (bubbles of O 2 or H 2 ) or precipitates blocked the capillary. Processes at larger current densities require a moving electrolyte. Examples are pulse deposition of metals, local corrosion and electrochemical machining (ECM), which means an anodic dissolution at current densities up to 100 A/cm 2 . A new concept was developed, based on capillaries made of glass tubes with a partition. Accordingly, we employed two separated channels, one channel is used as an electrolyte inlet, the other as the outlet. One of the channels includes a thin gold wire as a counter electrode. A special gear pump moves the electrolyte with velocities up to 70 m/s in the mouth of the capillary. Current densities >100 A/cm 2 become possible under these conditions. Dissolution processes like ECM normally require an identification of the products, which became possible by adding a flow-through micro cuvette of an UV-Vis spectrometer at the electrolyte outlet.