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

• Published in: Electrochimica acta 2004-07, Vol.49 (17), p.2863-2870
• Main Authors: Lohrengel, M.M, Rosenkranz, C, Klüppel, I, Moehring, A, Bettermann, H, Bossche, B.Van den, Deconinck, J
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Electrochemical machining; Electrochemical methods; Exact sciences and technology; Microcell; Microreactor
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2004.01.068

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.