The effect upon limiting currents and potentials of coupling a rotating disc and cylindrical electrode with ultrasound

The reduction of the silver cation, Ag⁺, was studied in dilute aqueous Na₂S₂O₃/NaHSO₃ solution at a platinum and stainless steel rotating electrode in the absence and presence of ultrasound. Under silent conditions, electrode potential measurements indicate that silver deposition is the main reaction occurring at the cathode during the electrolysis of a model photographic processing solution. Under insonation conditions at 20 kHz the reduction wave shifts anodically with increasing ultrasonic power. Similarly the discharge of hydrogen shifted anodically with increasing power. It is also shown that below 1000 r.p.m. insonation leads to improved limiting currents when compared to the silent system. As the rotation speed of the electrode increases above 1000 r.p.m., the limiting current decreases as the ultrasonic power increases.