OER and HER Catalyst Activity Metrics: Overpotential, Tafel Slope, and Product Verification

It is useful to consider some of the metrics used to describe the activity of a particular catalyst for the OER or HER. In terms of electrochemical characterization, TABLES 1, 2 give the overpotentials required to achieve a given current density (chosen as -10 mA cm^-2 for the HER and 1 mA cm^-2 for the OER) and Tafel slopes as ways of comparing different catalysts. However, it is clearly insufficient to assume that a given current is producing a particular gas - it has to be proven that the products of the reaction are indeed those claimed.