Microwave-enhanced electro-deposition and stripping of palladium at boron-doped diamond electrodes

In situ microwave activation has been applied to the electro-deposition and stripping of palladium metal (which is widely used as a catalyst) at cavitation resistant boron-doped diamond electrodes. Focused microwave radiation leading to heating, boiling, and cavitation is explored as an option to improve the speed and sensitivity of the analytical detection procedure. The deposition and anodic stripping of palladium by linear sweep voltammetry in 0.1 M KCl (pH 2) solution and at boron-doped diamond electrodes is shown to be strongly enhanced by microwave activation due to both (i) the increase in mass transport and (ii) the increase in the kinetic rate of deposition and stripping.The temperature at the electrode surface is calibrated with the reversible redox couple Fe(CN)64−/Fe(CN)63− and found to be reach 380 K. In the presence of microwave radiation, the potential of onset of the deposition of palladium is strongly shifted positive from −0.4 to +0.1 V versus SCE. The optimum potential for deposition in the presence of microwaves is −0.4 V versus SCE and the anodic stripping peak current is shown to increase linearly with deposition time. Under these conditions, the stripping peak current varies linearly with the palladium concentration down to ca. 2 μM. At concentration lower than this a logarithmic variation of the stripping peak current with concentration is observed down to ca. 0.1 μM (for 5 min pre-concentration in presence of microwave radiation).