Self-oscillating actuation of IPMC

The experimental relationship between potential-current profile and interconnect poisoning molecules of the Pt electrode surface was analyzed. The 

During a series of electrochemical reactions, oxidation of small organic molecules (SOMs) such as formaldehyde (HCHO) on a Pt electrode affects the potential (or current) on a Pt electrode. Namely, the surface reactions cause oscillatory pattern of the aforementioned variables. The anodic oxidation of HCHO on a Pt surface is believed to be accompanied by the appearance of intermediate species, i.e. CO and OH. Therefore the overall reaction, which involves the reaction of PtOH with the intermediate Pt-CO and the conversion of Pt-OH to Pt oxides, leading to the occurrence 

An electrochemical quartz crystal microbalance (EQCM) experiment was carried out to determine the mass change on the electrode. The equation of the resonant frequency change for mass change has been presented by the Sauerbrey equation  

The actuation study of IPMC under a constant current is shown in Fig. 3.19. The figure shows that the oscillatory potential results in oscillatory deformation of IPMC. During the oxidation of formaldehyde, the intermediate (CO) of the reaction strongly binds to the platinum surface of the IPMC and blocks active sites. In this process, the resistance of platinum is increased, which leads to weaker field strength between electrodes of IPMC. Platinum also adsorbs OH which then oxidizes the CO on adjacent platinum sites to CO2. Due to this reaction, conductivity of platinum improves and results in a stronger field strength between the electrodes. This is believed to be the cause for self-oscillatory actuation of IPMC. 

Chronopotentiometry scans for three different concentrations of HCHO helped to characterize behavior of IPMC in HCHO solution. For all cases, the oscillations started at about 7 mA/cm (further noted as threshold current) with a constant value of 0.11-0.13 Hz up to the current density of 14mA/cm. After further increasing the current, in IMHCHO, the frequency decreases as shown in Fig. 3.20. In 2 M HCHO, the frequency maintains a constant valne regardless of higher current density, and in 3 M HCHO 

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