Despite the growing popularity of cyclic voltammetry, many students do not receive formalized training in this technique as part of their coursework. Confronted with self-instruction, students can be left wondering where to start. Here, a short introduction to cyclic voltammetry is provided to help the reader with data acquisition and interpretation. Tips and common pitfalls are provided, and the reader is encouraged to apply what is learned in short, simple training modules provided in the Supporting Information. Armed with the basics, the motivated aspiring electrochemist will find existing resources more accessible and will progress much faster in the understanding of cyclic voltammetry.

The pursuit of solar fuels has motivated extensive research on molecular electrocatalysts capable of evolving hydrogen from protic solutions, reducing CO2, and oxidizing water. Determining accurate figures of merit for these catalysts requires the careful and appropriate application of electroanalytical techniques. This Viewpoint first briefly presents the fundamentals of cyclic voltammetry and highlights practical experimental considerations before focusing on the application of cyclic voltammetry for the characterization of electrocatalysts. Key metrics for comparing catalysts, including the overpotential (η), potential for catalysis (E(cat)), observed rate constant (k(obs)), and potential-dependent turnover frequency, are discussed. The cyclic voltammetric responses for a general electrocatalytic one-electron reduction of a substrate are presented along with methods to extract figures of merit from these data. The extension of this analysis to more complex electrocatalytic schemes, such as those responsible for H2 evolution and CO2 reduction, is then discussed.

Molecular catalysts for electrochemically driven hydrogen evolution are often studied in acetonitrile with glassy carbon working electrodes and Brønsted acids. Surprisingly, little information is available regarding the potentials at which acids are directly reduced on glassy carbon. This work examines acid electroreduction in acetonitrile on glassy carbon electrodes by cyclic voltammetry. Reduction potentials, spanning a range exceeding 2 V, were found for 20 acids. The addition of 100 mM water was not found to shift the reduction potential of any acid studied, although current enhancement was observed for some acids. The data reported provides a guide for selecting acids to use in electrocatalysis experiments such that direct electrode reduction is avoided.

Kinetic analysis of hydrogen production catalyzed by Co­(dmgBF2)2(CH3CN)2 (dmgBF2 = difluoroboryl-dimethylglyoxime) was performed in acetonitrile with a series of para-substituted anilinium acids. It was determined that the mechanism of hydrogen evolution is governed by three elementary steps; two are acid concentration and pK a dependent, whereas the third was shown to be intrinsic to the catalyst, likely reflecting either H–H bond formation or H2 release. The kinetics of the first proton transfer step, the protonation of the singly reduced catalyst, were evaluated using foot-of-the-wave analysis, as well as current–potential analysis for voltammograms displaying total catalysis behavior. Analysis of the total catalysis peak shift required the empirical determination of a new equation for the ECEC′ catalytic mechanism using digital simulations. The kinetics of the second proton transfer stepassigned to protonation of the doubly reduced, singly protonated speciesand the acid-independent step were determined by analyzing the plateau current of the catalytic wave over a range of acid concentrations. Both proton transfer steps follow linear free energy relationships of log­(k) vs acid pK a. These linear relationships give slopes of −0.94 and −0.77 for the first and second proton transfers, respectively, indicating that both steps become faster with increasing acid strength.

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