The computation of the solution resistance from polarization data

Abstract The influence of the solution resistance between the reference and working electrodes on experimental polarization curves relating to a class of electrochemical systems described by the law i = I c ( e αΔE e - e − βΔE c ) has been examined and a numerical method for computing R s has been proposed. The best-fitting method, based on the function In i = P + QΔE + Ri , P , Q and R being the unknown parameters, processes data belonging to the anodic and cathodic Tafel regions. Applications to artificial data, obtained from the analytical expression of i ( ΔE ), which accounts for the influence of R s , and relating to the ΔE interval [− 300, 300] mV, show its usefulness and validity. Some cases simulated the shape of real polarization curves, characterised by I c = 0.1 mA cm −2 , B a = 40 mV and B c = 120 mV, as a function of R s over the interval [0.1, 5] Ω. Their processing was successful and demonstrated that from a practical point of view the anodic and cathodic regions provide the same value of R s . Furthermore the proposed method reproduces with a good accuracy the actual values of I c , B a and B c . Rather similar results were observed when the distortion of polarization curves for R s = 1 Ω was studied as a function of I c over the interval [0.01, 4.0] mA cm −2 , even if the cathodic region seems to provide better information at high values of I c . At last the proposed method can be improved using the successive approximation technique because in this case the distinction between the anodic and cathodic regions tends to disappear when ΔE intervals of suitable amplitude are considered.