Consistent boundary conditions for electrochemical interfaces, which cover double layer charging, pseudo-capacitive effects and transfer reactions, are of high demand in electrochemistry and adjacent disciplines. Mathematical modeling and optimization of electrochemical systems is a strongly emerging approach to reduce cost and increase efficiency of super-capacitors, batteries, fuel cells, and electro-catalysis. However, many mathematical models which are used to describe such systems lack a real predictive value. Origin of this shortcoming is the usage of oversimplified boundary conditions. In this work we derive the boundary conditions for some general electrode-electrolyte interface based on non-equilibrium thermodynamics for volumes and surfaces. The resulting equations are widely applicable and cover also tangential transport. The general framework is then applied to a specific material model which allows the deduction of a current-voltage relation and thus a comparison to experimental data. Mathematical modeling of electrochemical systems is a strongly growing subject with many applications in science and industry. Applications range from fundamental single crystal systems 2 to plating and metal deposition, 3 lithium ion batteries, 4-8 fuel cells, 9 super caps, 10 and many further. Continuum models are the very basis of interpreting experimental results and widely used in chemical engineering to estimate cell dimensioning and heat generation, utilized in computed aided optimization of charging profiles or material compositions, and applied to many more issues of electrochemical systems.But the development of new electrochemically active materials and subsequent reaction mechanisms proceeds rapidly, e.g. with lithium air 11 or sulfur batteries, 12 solid electrolytes 13 or ionic liquids 14 and new electro-catalytic materials. 15 The adaption of existing mathematical models to new materials or material combinations is quite often not straight forward, if at all possible, and could even lead to a misinterpretation of experimental results. A systematic modeling approach which is applicable to various new electrochemical systems is hence of great importance, including reaction intermediates which can form at the electrode-electrolyte interface.The continuum mechanical modeling procedure generally spreads in two parts, (i) the derivation or prescription of volumetric balance equations, and (ii) stating the corresponding boundary conditions. The volumetric balance equations account for ion diffusion in the electrolyte phase, solid state diffusion in intercalation materials, mechanical deformation and stress, viscosity effects, heat transport, and others. Their derivation is mainly based on the modern framework of nonequilibrium thermodynamics, which provides some guidance through the actual modeling procedure. A core advantage of this framework is the stringent separation between general, material independent relations (expressed in chemical potentials μ α of some species A) and the actual material modeling (expr...