The reaction of superoxide with carbon dioxide is studied using voltammetry and potential step chronoamperometry at polycrystalline gold disk microelectrodes in a DMSO electrolyte. In agreement with prior work, it is found that a reaction occurs between the superoxide anion radical and carbon dioxide, effectively precluding their simultaneous detection at low levels of carbon dioxide. The reaction rate is found to be first-order with respect to both carbon dioxide and superoxide, consistent with an ECE or DISP1 type process. A rate constant is determined for this reaction based upon two independent methods: fast scan cyclic voltammetric measurements and steady-state voltammetric signals. These methods yield a consistent rate constant of 3.7 ( 1.6 × 10 5 M -1 s -1 . Potential step chronoamperometric measurements reveal that oxygen adsorbs onto a gold electrode surface, to form a monolayer both in the presence and absence of carbon dioxide. A rate constant for the reduction of surface-bound oxygen to superoxide is reported.

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The electro-reduction of carbon dioxide is studied by linear sweep and cyclic voltammetry in DMSO electrolyte solutions and at polycrystalline gold microdisk electrodes. An electrode reaction pathway is suggested. Numerical simulation of the reaction mechanism gives current | potential waveshapes in excellent agreement with those observed experimentally. Kinetic parameters for the reduction process are deduced from this waveshape approach, and the charge-transfer coefficient is found to be approximately 0.43 ( 0.05.

Designs for reusable microelectrodes, which are easy to assemble and so do not require special technical skills or services for their construction, are presented. Three types of microelectrodes are fabricated by lamination of metal foil, wire, and wire grids, producing microband, microdisk, and a linear array of microdisk geometries. The electrodes themselves do not need to be polished prior to their use but are observed to be slightly recessed from the surrounding insulating surface. Good agreement is observed between experimental steady-state voltammetric results in nonaqueous solutions and the relevant analytical theory for the voltammetric current.

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