Discussion above highlights the central role of electrode inner potentials in determining the applied electrode potential in electrochemical systems. This is a direct consequence of the general theory of single electrode potentials in Eq. ( ), which shows that ϕ M is directly proportional to the single electrode potential independent of the chosen reference scale. From a computational perspective, it is important to note that unlike E DF T f , the inner potential is a local quantity defined within the bulk electrode and allows controlling the electrode potential between two bulk phases (either solid, liquid, or gas). As shown by the various examples in the following Sections 2.2-2.6, fixing the inner potential enables modelling the applied electrode potential within the electrode in accordance with the general definition given in Eq. ( ). Hence, performing simulations at constant ϕ M ensures that the experimentally applied potential i.e. μbath e is directly mimicked and that electronic quantities inherent to the used simulation cell (μ M e = E DF T f ) are avoided. To control the electrode inner potential in GCE-DFT simulations, we introduce the constant inner potential (CIP) approach illustrated in Figure . The CIP method has been im- plemented in the GPAW software by modifying the solvent jellium model (SJM). The original SJM model controls E DF T f and CIP-DFT extends SJM to fix the inner potential ϕ M against the solution inner potential ϕ S . By using Dirichlet boundary conditions, the solution inner potential far from the electrode is fixed to zero (ϕ S = 0). As displayed in Figure , controlling ϕ M while keeping ϕ S = 0 yields a well-defined electrode potential and a constant reference point. There is no need to introduce E DF T f to define the absolute potential as the inner potential difference uniquely defines the electrode potential and ϕ M can be converted to any experimental scale. A more detailed description of the CIP-DFT method is available in the Supporting Information. In the following sections, we demonstrate the performance of CIP-DFT for simulating a variety of electrochemical systems ranging from inner-sphere reactions on metallic electrodes to outer-sphere reactions, semiconductor electrodes, and the creation of a biased two-electrode setup. Furthermore, we show that the method can be combined with both explicit and implicit solvent models.