Electrochemistry of Copper in Polyacrylic Acid: The Electrode Mechanism and Analytical Application for Gaseous Hydrogen Peroxide Detection

Abstract

Electrode reaction of copper(II) reduction in an aqueous solution of polyacrylic acid (PAA) is studied by means of cyclic staircase and square-wave voltammetry to establish a basis for an electrochemical sensor for gaseous hydrogen peroxide detection. It has been determined that the reduction mechanism at a glassy carbon electrode follows a two-step, consecutive electron transfer reaction scheme of Cu2+to the final copper solid deposit, via the formation of the intermediate Cu+ions, which are subject to a fast disproportionation reaction. Experimental data have been supported by theoretical considerations and simulations based on EC'E electrode mechanism, where E designates an electrode reaction, whereas C' is a homogeneous regenerative chemical reaction. Estimated thermodynamic and kinetic data of the electrode mechanism suggest stabilization of the intermediate Cu+form by PAA in comparison with a pure aqueous medium. Commercially available screen-printed carbon electrodes were covered with a film of 1% (mass percent) of aqueous PAA solution containing Cu2+ions, which proves to be a promising platform for gaseous H2O2detection, where the Cu2+/Cu+couple serves as a redox mediator for H2O2reduction, with a limit of detection at a sub-μg dm-3concentration level in the gas phase.