B4 Steady State Linear Sweep Voltammograms Electrochemical Catalysis

Linear sweep voltammetry imposes a linear ramp of potential onto the electrochemical cell in a quiet solution and measures the resulting current vs. potential response (Table 11.1). As in many electrochemical experiments, the shape of the response curve is characteristic of the electrode reaction mechanism [1, 2], In general, the shapes are complex and not easily described by closed form models.

However, linear sweep voltammetry gives a characteristic shape for electrochemical catalysis if certain experimental conditions are fulfilled. Box 11.2 illustrates a simple pathway for reductive electrochemical catalysis. A catalyst P added to the solution acts as a mediator to shuttle electrons from an electrode to a substrate A, yielding the product B and regenerating P. Substrate of reactant A is directly reducible only at potentials considerably negative of E°'. A similar pathway pertains to catalytic oxidations.

The homogeneous second step with rate constant k\ in Box 11.2 regenerates P in a thin layer of solution near the electrode, so that it can be easily reduced at the electrode. This catalytic cycling of P increases the current and changes the shape of the response curve compared to what would be obtained in the absence of A.

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