Applicability range of potential step chronoamperometry for determining reliable diffusion coefficients of hydrogen and lithium in host materials

• Impact of different diffusion regimes on PSCA illustrated on the example of H in Pd. • Literature data Review using Potential Step Chronoamperometry to determine the Diffusion Coefficient of H or Li. • Intrinsic dependency of diffusion coefficient on sample thickness misleads in diffusion coefficient determination. • Proposal for reliable application of potential step chronoamperometry is suggested. Potential step chronoamperometry is often used to study the electrochemical unloading process and to determine the diffusion coefficient D of an intercalating atom species in a host material, as it is seemingly easily applicable. The present work emphasises the importance of ensuring a diffusion-controlled unloading process during the potential step chronoamperometry measurement, if determination of the diffusion coefficient is targeted. As an example, diffusion-controlled and non-diffusion-controlled hydrogen unloading series from palladium samples and the resulting diffusion coefficients are presented, for comparison. A literature review summarising the diffusion coefficients of different intercalating species determined for several different systems by this method reveals a systematic error in the results. It turned out that insufficient diffusion control is a common issue in the application of the chronoamperometry method. Based on this finding, it is suggested to verify measurements in the diffusion-controlled regime when chronoamperometry is applied. A suitable verification technique is provided.