Design and characterization of a rotating electrochemical quartz-crystal-microbalance electrode

A novel design for a rotating electrochemical quartz-crystal microbalance (rEQCM) which includes easily and reproducibly exchangeable quartz-crystal holders is described. The rEQCM allows for well-controlled mass-transport conditions at the working electrode on a 10 MHz quartz crystal. Together with the flexibility of the proposed design, this makes it useful for a wide range of applications in electrochemistry. At a data acquisition rate of 5 Hz, noise level and stability of the resonant frequency were better than 1 Hz at rotation rates of 0-3500 rpm. This corresponds to a mass density on the quartz crystal of 4.7 ng cm(-2). The small recess needed to fix the quartz crystal in the electrode holder was shown not to affect the primary current distribution and the mass-transport conditions. Electrodeposition of Cu and Ag was used for the in situ characterization of the frequency dependence of the Sauerbrey constant (mass sensitivity) of the quartz as a function of mass load on the crystal. It was found that, in the initial phase of Ag and Cu deposition on Au, the mass sensitivity is affected by internal stresses in the deposit. (C) 2000 The Electrochemical Society. S0013-4651(99)05-039-9. All rights reserved.