The experiment of collecting the reversible behavior between the flowing current and linearly changed potentials with time is generally known as cyclic voltammetry (CV). Cyclic voltammetry is commonly carried out in a three-electrode system (Figure ). In such a system, the working electrode will host the redox reaction of interest, and the counter electrode can balance the current flowing from the Faradaic reaction on the working electrode surface. The reference electrode will allow for accurate measurements of the working electrode potential. In the three-electrode system, researchers often utilize the Gouy-Chapman-Stern model at the interface between the working electrode and electrolyte to describe the interfacial effect (Figure ). The double layer on an electrode surface includes a compact double layer within the outer Helmholtz plane (OHP) and a diffusion layer connected to ion redistribution. To ensure a negligible contribution from the migration to the mass transport of the charged active species during a Faradaic reaction, an excess of supporting electrolyte is usually used to simplify the mathematical treatment of the Faradaic current and establish a uniform ionic strength throughout the solution even under steady-state Faradaic conditions. Cyclic voltammetry is a powerful tool to characterize surface-anchored molecular catalysts. Unlike their solubilized counterparts that are free to move around in an electrolyte solution, anchored compounds have limited diffusion range depending on the linkage length and solvent, and usually do not diffuse through the electrical double layer. They gain or lose electrons through electron transfer due to the directional potential difference with the electrode. Therefore, the peak current of surface anchored compounds in typical cyclic voltammograms would be linearly proportional to the scan rate rather than the square root of the scan rate as for their free soluble analogues, a feature that could be employed to validate that the catalysts are anchored (Figure ). Furthermore, the symmetry of the i-E trace (i.e., the relationship between current and voltage during scanning) can reflect the system's chemical stability (i.e., surface anchored catalysts do not decompose or get dissolved) and electrochemical reversibility (i.e., Nernstian wave). Two parameters may be extracted from the analysis. One is the ratio between the cathodic and anodic peak current (i.e., ipa/ipc). Another is the separation of the two peak potentials (i.e., Epa -Epc). For a chemically stable system, the ratio of peak currents is generally equal to 1. However, one should be cautious in calculating it because the anodic peak current (if the cathodic scan is started first) must be corrected to a zero current baseline to mitigate the disturbance of the capacitance effect at the interface. For a Nernstian wave with a one-electron transfer, the difference of the two peak potentials should be 57 -60 mV at room temperature. It is important to note that cyclic voltammetry may not be comprehensive to characterize some non-covalently anchored systems with strong surface interactions (e.g., axial coordination, π-π interactions) between the electrode and the molecular catalyst. With such surface interactions, the Fermi level of the electrode strongly couples with the energy level of the redox center in the anchored system. Therefore, there will be no potential drop between the electrode and the molecular catalyst, and no electron transfer will happen. In that case, cyclic voltammetry can only reflect the Faradaic reaction of the supporting electrolyte (Figure ).