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 H2O2 detection,
where the Cu2+/Cu+ couple serves as a redox
mediator for H2O2 reduction, with a limit of
detection at a sub-μg dm–3 concentration level
in the gas phase.
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