Metal-hydride electrodes made of an AB₂ alloy of the composition Zr_0¨5Ti_0¨5V_0¨6Cr_0¨2Ni_1¨2 are studied for AC impedance behaviour at several of their state-of-charge values. Impedance data at any state-of-chargecomprisetwoRC-time constants and accordingly are analysed by using a nonlinear-least-square-fitting procedure. Resistance of the electrode and frequency maximumf* of the lowfrequency semicircle are found useful for predicting state-of-charge of the metalhydride electrodes.

Electrochemical reduction of hydrogen peroxide is studied on a sand-blasted stainless steel (SSS) electrode in an aqueous solution of NaClO₄. The cyclic voltammetric reduction of H₂O₂ at low concentrations is characterized by a cathodic peak at $-0.40$ V versus standard calomel electrode (SCE). Cyclic voltammetry is studied by varying the concentration of H₂O₂ in the range from 0.2 mM to 20 mM and the sweep rate in the range from 2 to 100 mV s^-1. Voltammograms at concentrations of H₂O₂ higher than 2 mM or at high sweep rates consist of an additional current peak, which may be due to the reduction of adsorbed species formed during the reduction of H₂O₂. Amperometric determination of H₂O₂ at $-0.50$ V vs SCE provides the detection limit of 5 𝜇M H₂O₂. A plot of current density versus concentration has two segments suggesting a change in the mechanism of H₂O₂ reduction at concentrations of H₂O₂ ≥ 2 mM. From the rotating disc electrode study, diffusion co-efficient of H₂O₂ and rate constant for reduction of H₂O₂ are evaluated.