Preparation of porous nanostructured Ag electrodes for sensitive electrochemical detection of hydrogen peroxide

Porous Ag layers have been prepared by hydrogen bubble templated electrodeposition from an ammonium acetate bath, under application of a large current density (-2 A cm-2). SEM images of the layers show macroscopic porosity and a spongy dendritic structure, analogous to those observed for other porous metals/alloys deposited with a similar procedure. A deposition charge of 30 C cm-2 produces a porous deposit with a mass of ca 1.7 mg cm-2. The roughness factor fr is evaluated by impedance and from the charge density of Pb UPD; both methods provide estimates of fr in the order of several hundreds but values obtained from impedance analysis are more than twice larger. Mass transport to the porous electrodes is studied by linear sweep voltammetry at stationary and rotating disk electrodes. In comparison with flat Ag cathodes, porous Ag electrodes show larger sensitivity, lower limit of detection and extended range of linear response in H2O2 reduction.