  Electrochemical quartz crystal microbalance (EC-QCM) is a versatile
gravimetric technique that allows for parallel characterization of mass
deposition and electrochemical properties. Despite its broad applicability,
simultaneous characterization of two electrodes remains challenging due to
practical difficulties posed by the dampening from fixture parasitics and the
dissipative medium. In this study, we present a dual electrochemical QCM (dual
EC-QCM) that is employed in a three-electrode configuration to enable
consequent monitoring of mass deposition and viscous loading on two crystals,
the working electrode (WE) and the counter electrode (CE). A novel cor-rection
approach along with a three standard complex impedance calibration is employed
to overcome the effect of dampening while keeping high spectral sensitivity.
Separation of viscous loading and rigid mass deposition is achieved by robust
characterization of the complex impedance at the resonance frequency.
Validation of the presented system is done by cyclic voltammetry
characterization of Ag underpotential deposition on gold. The results indicate
mass deposition of 412.2 ng for the WE and 345.6 ng for the CE, reflecting a
difference of the initially present Ag adhered to the surface. We also
performed higher harmonic measurements that further corroborate the sensitivity
and reproducibility of the dual EC-QCM. The demonstrated approach is especially
intriguing for electrochemical energy storage applications where mass detection
with multiple electrodes is desired.
