Efforts toward controlling the selectivity of chemical syntheses have focused on modifying the molecular structure of chemical components in the system. Identifying the effective structural feature and making desired modifications require tremendous work. Alternatively, we discussed that an external electric field could alter reaction selectivity by inducing field-dipole interactions. However, applying large electric fields to reactions and studying their effects remains challenging. Kanan and coworkers developed a parallel plate cell, which allows the application of a large electric field to the system, to evaluate the electric field-induced change in selectivity in an Al2O3-catalyzed epoxide rearrangement (Figure ). In this study, depositing a thin layer of Al2O3 on a p-doped Si electrode was obtained, and the electrode surface after modification was considered catalytically active. Al2O3 coated on the electrode with alkylphosphonic acid was used as a counter electrode. Applying a voltage between the two electrodes generated an electrochemical double layer where the placement of ionic and polar molecules was controlled by the interfacial electric fields at each electrode-electrolyte interface. An increasing ratio of aldehyde to ketone was observed when the applied potential was less than -3 V and more than 3 V compared to no potential applied. It was also found that changing the type of phosphonic acid coating on the counter electrode affected the capacitance of the cell and further led to the changing of the electric field strength. Up to a 10-fold increase in the ratio of the two products was observed. Furthermore, the electric field was influenced by solvents, resulting in a dramatic change in selectivity. In CH2Cl2, up to a 63-fold enhancement was observed compared to CH3CN. This study represents a proof-of-concept that the use of a parallel plate cell provides an alternative method for engaging interfacial electric fields on a relatively large scale for selective transformations. The use of an insulating coating decouples electrostatic from the electrochemical effects. Thus, the change in selectivity solely resulted from the change in electric potential, showing the irreplaceable role of the interfacial electric field. Taking advantage of the ingenious design of the parallel plate cell, the same group expanded their study on carbene rearrangement reactions catalyzed by adsorbed and immobilized rhodium catalysts in the presence of an interfacial electric field (Figure ). Adapting a similar design as the previous study, Si electrodes coated with metal oxide layers were used as the opposing plates with rhodium porphyrin catalyst in between the dielectric-electrolyte interface. Applying voltage to the parallel plate cell resulted in changes between the cyclopropanation product C and insertion product D of the carbene rearrangement reaction. In the absence of an applied voltage, the Rh-catalyzed intramolecular carbene reaction from diazoketone formed products C:D in an approximate ratio of 10:1. Upon applying a voltage, the surface coating affected the ratio: the covalently attached Rh catalyst via the phosphonate-oxide linkage on the TiO2 surface with a higher dielectric constant was observed to induce an increase in the ratio up to >100:1 at +4 V as a result of increasing charge density, indicating an almost absolute selectivity toward C; on the contrary, the Al2O3 or alkylphosphonate coated surface caused a decrease of the ratio. Such a decrease in the C:D ratio was observed for Al2O3coated surfaces regardless of the positive or negative voltage applied. A comparison between covalently attached versus surface adsorbed Rh catalysts was conducted with a similar trend in selectivity change observed: both covalently immobilized and physically absorbed Rh complex on Al2O3 coated surfaces caused a decrease in the ratio, whereas on painted TiO2 surfaces, an increase in the ratio was found. Specifically, the covalently attached Rh complex on the Al2O3 surface decreased the ratio of C: D to 6.3:1 at -5 V. In comparison, the ratio dropped to 1.6:1 at +5 V in the case of the absorbed Rh complex on the Al2O3 surface. Results obtained from the adsorbed Rh on TiO2/Si surface resembled that of the covalently immobilized Rh. This study demonstrates a successful control of selectivity of a Rh-catalyzed intramolecular carbene reaction otherwise challenging to achieve. It is essential to highlight the effect of the solid surface selected for such a study: the direction of the selectivity change was a direct result of the dielectric property of the surface, as observed from the difference in Al2O3 versus TiO2. Either with or without covalent linkage, the Rh complex was found to localize at the dielectric-electrolyte interface, representing an exciting avenue to exploit.