In electrochemistry, faradaic impedance is the resistance and capacitance acting jointly at the surface of an electrode of an electrochemical cell.   The cell may be operating as either a galvanic cell generating an electric current or inversely as an electrolytic cell using an electric current to drive a chemical reaction.  In the simplest nontrivial case faradaic impedance is modeled as a single resistor and single capacitor connected in parallel, as opposed say to in series or as a transmission line with multiple resistors and capacitors.