The ReaxFF reactive force field method is based on a bond-order-dependent potential energy term in combination with a time-dependent, polarizable charge description. Bonding terms (e.g. bond, angle and torsion contributions; inherently depending on the bond order) and non-bonding interaction terms (e.g. van der Waals, Coulomb interactions and hydrogen bonds) contribute to the potential energy formulation. The bond order gets updated every iteration step controlled by the local atomic environment. Hereby, bond formation as well as bond dissociation can be captured. The self-consistent electron equilibration method (EEM) by Mortier et al. is used for determining the partial charges of each atom and for describing the electrostatic interactions. Our self-developed Pt/O/H reactive force field by D. Fantauzzi et al. serves as atomistic potential for the platinum, the oxygenated intermediates and water, extended by the reactive force field parameters for K + and F -ions. There, the interactions between the electrolyte ions and water have been extensively validated while in our previous work (Ref. 37) the force field for platinum bulk and surfaces including surface oxide formation of the Pt(111) surface was intensively tested. Note, that between the charged ions and the surface no direct bonding terms are considered, as these ions are considered to keep their solvation shell. All ReaxFF calculations were performed in the ADF software package (version 2019.103). In general, a timestep of 0.25 fs was used for integration of the equations of motions applying the velocity-Verlet algorithm. The Nosé-Hoover thermostat with a damping constant of 100 fs set the temperature for the MD simulations at 298.15 K. The Pt(111) surface was modelled by a symmetric twelve-layer slab (10 × 10 × 12 atoms), in which the central two layers were fixed to the corresponding calculated bulk crystal structure. Normal to the surface planes, the Pt slab is in contact with a 50 Å thick water layer (ρ = 0.997 g/cm 3 ), e.g. 2306 water molecules. The systems were built using the packmol software. All systems presented here have been equilibrated for 400,000 iterations in the canonical N V T ensemble, followed by the production run for another 400,000 iterations. For evaluating the spatially resolved entropy of water layers Two Phase Thermodynamics (2PT) calculations have been performed, here the N V T run was followed by 50,000 iterations in the microcanonical N V E ensemble plus 5,000 iterations for evaluation within the 2PT method. For a detailed description of the method as well as the coupling between the 2PT method (developed by Lin et al. ) and ReaxFF we refer to our recent publication. Structure visualizations were performed with the VMD software. Introducing the electrode potential in ReaxFF MD simulations